Positioning for acute respiratory distress in hospitalised infants and children

Abstract

Background

Acute respiratory distress syndrome (ARDS) is a significant cause of hospitalisation and death in young children. Positioning and mechanical ventilation have been regularly used to reduce respiratory distress and improve oxygenation in hospitalised patients. Due to the association of prone positioning (lying on the abdomen) with sudden infant death syndrome (SIDS) within the first six months, it is recommended that young infants be placed on their back (supine). However, prone positioning may be a non‐invasive way of increasing oxygenation in individuals with acute respiratory distress, and offers a more significant survival advantage in those who are mechanically ventilated. There are substantial differences in respiratory mechanics between adults and infants. While the respiratory tract undergoes significant development within the first two years of life, differences in airway physiology between adults and children become less prominent by six to eight years old. However, there is a reduced risk of SIDS during artificial ventilation in hospitalised infants. Thus, an updated review focusing on positioning for infants and young children with ARDS is warranted. This is an update of a review published in 2005, 2009, and 2012.

Objectives

To compare the effects of different body positions in hospitalised infants and children with acute respiratory distress syndrome aged between four weeks and 16 years.

Search methods

We searched CENTRAL, which contains the Acute Respiratory Infections Group's Specialised Register, MEDLINE, Embase, and CINAHL from January 2004 to July 2021.

Selection criteria

Randomised controlled trials (RCTs) or quasi‐RCTs comparing two or more positions for the management of infants and children hospitalised with ARDS.

Data collection and analysis

Two review authors independently extracted data from each study. We resolved differences by consensus, or referred to a third contributor to arbitrate. We analysed bivariate outcomes using an odds ratio (OR) and 95% confidence interval (CI). We analysed continuous outcomes using a mean difference (MD) and 95% CI. We used a fixed‐effect model, unless heterogeneity was significant (I² statistic > 50%), when we used a random‐effects model.

Main results

We included six trials: four cross‐over trials, and two parallel randomised trials, with 198 participants aged between 4 weeks and 16 years, all but 15 of whom were mechanically ventilated. Four trials compared prone to supine positions. One trial compared the prone position to good‐lung dependent (where the person lies on the side of the healthy lung, e.g. if the right lung was healthy, they were made to lie on the right side), and independent (or non‐good‐lung independent, where the person lies on the opposite side to the healthy lung, e.g. if the right lung was healthy, they were made to lie on the left side) position. One trial compared good‐lung independent to good‐lung dependent positions.

When the prone (with ventilators) and supine positions were compared, there was no information on episodes of apnoea or mortality due to respiratory events. There was no conclusive result in oxygen saturation (SaO_2; MD 0.40 mmHg, 95% CI ‐1.22 to 2.66; 1 trial, 30 participants; very low certainty evidence); blood gases, PCO₂ (MD 3.0 mmHg, 95% CI ‐1.93 to 7.93; 1 trial, 99 participants; low certainty evidence), or PO₂ (MD 2 mmHg, 95% CI ‐5.29 to 9.29; 1 trial, 99 participants; low certainty evidence); or lung function (PaO₂/FiO₂ ratio; MD 28.16 mmHg, 95% CI ‐9.92 to 66.24; 2 trials, 121 participants; very low certainty evidence). However, there was an improvement in oxygenation index (FiO₂% X M_PAW/ PaO₂) with prone positioning in both the parallel trials (MD ‐2.42, 95% CI ‐3.60 to ‐1.25; 2 trials, 121 participants; very low certainty evidence), and the cross‐over study (MD ‐8.13, 95% CI ‐15.01 to ‐1.25; 1 study, 20 participants).

Derived indices of respiratory mechanics, such as tidal volume, respiratory rate, and positive end‐expiratory pressure (PEEP) were reported. There was an apparent decrease in tidal volume between prone and supine groups in a parallel study (MD ‐0.60, 95% CI ‐1.05 to ‐0.15; 1 study, 84 participants; very low certainty evidence). When prone and supine positions were compared in a cross‐over study, there were no conclusive results in respiratory compliance (MD 0.07, 95% CI ‐0.10 to 0.24; 1 study, 10 participants); changes in PEEP (MD ‐0.70 cm H₂O, 95% CI ‐2.72 to 1.32; 1 study, 10 participants); or resistance (MD ‐0.00, 95% CI ‐0.05 to 0.04; 1 study, 10 participants).

One study reported adverse events. There were no conclusive results for potential harm between groups in extubation (OR 0.57, 95% CI 0.13 to 2.54; 1 trial, 102 participants; very low certainty evidence); obstructions of the endotracheal tube (OR 5.20, 95% CI 0.24 to 111.09; 1 trial, 102 participants; very low certainty evidence); pressure ulcers (OR 1.00, 95% CI 0.41 to 2.44; 1 trial, 102 participants; very low certainty evidence); and hypercapnia (high levels of arterial carbon dioxide; OR 3.06, 95% CI 0.12 to 76.88; 1 trial, 102 participants; very low certainty evidence).

One study (50 participants) compared supine positions to good‐lung dependent and independent positions. There was no conclusive evidence that PaO₂ was different between supine and good‐lung dependent positioning (MD 3.44 mm Hg, 95% CI ‐23.12 to 30.00; 1 trial, 25 participants; very low certainty evidence). There was also no conclusive evidence for supine position and good‐lung independent positioning (MD ‐2.78 mmHg, 95% CI ‐28.84, 23.28; 25 participants; very low certainty evidence); or between good‐lung dependent and independent positioning (MD 6.22, 95% CI ‐21.25 to 33.69; 1 trial, 25 participants; very low certainty evidence).

As most trials did not describe how possible biases were addressed, the potential for bias in these findings is unclear.

Authors' conclusions

Although included studies suggest that prone positioning may offer some advantage, there was little evidence to make definitive recommendations. There appears to be low certainty evidence that positioning improves oxygenation in mechanically ventilated children with ARDS. Due to the increased risk of SIDS with prone positioning and lung injury with artificial ventilation, it is recommended that hospitalised infants and children should only be placed in this position while under continuous cardiorespiratory monitoring.

Plain language summary

Positioning for hospitalised infants and children with acute respiratory distress

Review question

We investigated whether there was a difference in the outcomes for infants and young children with acute respiratory distress syndrome (ARDS) on artificial ventilation who were positioned lying on their abdomen (the prone position), compared to lying on their back (the supine position), or on their side.

Background

ARDS is one of the most frequent causes of hospitalisation and death in infants and young children globally. When children with severe respiratory distress are hospitalised, treatment may include additional oxygen, with or without assisted ventilation. These attempts to increase oxygenation may damage the lungs. Infants and children with respiratory distress placed in particular positions may be more comfortable, breathe more easily, and have better outcomes. However, different positions may also increase the risk of adverse outcomes, such as obstruction of the endotracheal tube (the tube that connects the person to a ventilator), and accidental extubation (removal of the tube). To find out if this was the case, we searched the literature to identify randomised controlled trials (RCTs) and quasi‐RCTs comparing two or more body positions for managing infants and children hospitalised with ARDS.

Search date

Our evidence is current to 26 July 2021.

Study characteristics

We included six trials, with a total of 198 participants aged from four weeks to 16 years. The majority were on mechanical ventilators. The timing of interventions ranged from 15 minutes after the child had been settled in a hospital bed, to a maximum of seven days over the duration of the intervention. Only a small number (n = 15) of the children did not have their breathing supported by a ventilator.

Study funding source

The trials included in this review were supported by public agencies.

Key results

Lying on their abdomen appeared to improve the use of oxygen (oxygenation index is the need for additional oxygen relative to the child’s oxygen level) compared to lying on their back. This finding was based on data from three trials with 141 children. Only one trial with 102 children reported adverse effects, which did not differ between the two positions. One trial with 50 children compared lying on their back to other positions, and was not able to show consistent differences in blood oxygenation. There is not enough information to make any conclusions about the benefits and harms of any position in infants and children with acute respiratory distress.

It is important to remember that these children were hospitalised, and on assisted breathing. Because of the association between lying on their abdomen and SIDS, children should not be positioned on their abdomen unless they are in hospital, and their breathing is constantly monitored.

Certainty of the evidence

The findings of this review are limited by the small number of identified trials, five of which had fewer than 40 participants; the short duration of the interventions; and the lack of description of how the study authors addressed the risk of bias in their trials. Overall, we are uncertain how different positions affect our main outcomes, such as oxygenation levels. This means that future research is needed to improve the certainty of our results.

Summary of findings

Summary of findings 1. Summary of findings table ‐ Prone compared to supine for acute respiratory distress in hospitalised infants and children (ARDs).

Prone compared to supine for acute respiratory distress in hospitalised infants and children (ARDs)
Patient or population: acute respiratory distress in hospitalised infants and children (ARDs) Setting: hospital (paediatric critical care unit) Intervention: prone Comparison: supine
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with supine	Risk with prone
Mortality (respiratory events) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Oxygen saturation (SaO2)	The mean oxygen saturation (SaO2) ranged from 90.5 to 93.1 mmHg	mean 0.4 mmHg higher (1.22 lower to 2.66 higher)	‐	30 (1 RCT)	⊕⊝⊝⊝ Very lowa,b,c
Blood gases (PO2) follow‐up: range 1 hours to 7 days	The mean blood gases (PO2) ranged from 78 to 97.5 mmHg	mean 2 mmHg higher (5.29 lower to 9.29 higher)	‐	99 (1 RCT)	⊕⊕⊝⊝ Lowd,e
PaCO2 follow‐up: range 20 hours to 7 days	The mean paCO2 ranged from 6.5 to 53 mmHg	mean 3 mmHg higher (1.93 lower to 7.93 higher)	‐	99 (1 RCT)	⊕⊕⊝⊝ Lowd,e
Lung function (PaO2/FiO2 ratio) follow‐up: range 1 hour to 7 days	The mean lung function (PaO2/FiO2 ratio) ranged from 153 to 176 mmHg	mean 28.16 mmHg higher (9.92 lower to 66.24 higher)	‐	121 (2 RCTs)	⊕⊝⊝⊝ Very lowa,b,d
Oxygenation index (FiO2% X MPAW/PaO2) follow‐up: range 1 hour to 7 days	The mean oxygenation index (FiO2% X MPAW/PaO2) ranged from 9.5 to 11 mmHg	MD 2.42 mmHg lower (3.6 lower to 1.25 lower)	‐	121 (2 RCTs)	⊕⊝⊝⊝ Very lowa,f
Potential adverse outcomes (extubation) assessed with: % follow‐up: range 1 hours to 7 days	98 per 1000	58 per 1000 (14 to 216)	OR 0.57 (0.13 to 2.54)	102 (1 RCT)	⊕⊝⊝⊝ Very lowa,f
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; MD: mean difference; OR: odds ratio
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.
See interactive version of this table: https://gdt.gradepro.org/presentations/#/isof/isof_question_revman_web_423281134243830314.

^a We identified significant issues with the randomisation process and concealment of allocation
^b The study was downgraded due to very wide confidence intervals indicating possible benefit or harm
^c Downgraded due to very small single study assessment 
^d The study was downgraded due to very wide confidence intervals indicating possible benefit or harm
^e This outcome was downgraded due to imprecision; very small single study
^f Downgraded due to very small studies

Summary of findings 2. Summary of findings table ‐ Supine compared to good‐lung dependent for acute respiratory distress in hospitalised infants and children (ARDs).

Supine compared to good‐lung dependent for acute respiratory distress in hospitalised infants and children (ARDs)
Patient or population: acute respiratory distress in hospitalised infants and children (ARDs) Setting: hospital (paediatric critical care unit) Intervention: supine Comparison: good‐lung dependent
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with good‐lung dependent	Risk with supine
Mortality (respiratory events) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Oxygen saturation (SaO2) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
PaO2 follow‐up: range 15 minutes to 45 minutes	The mean paO2 was 111.92 mmHg	mean 3.44 mmHg higher (23.12 lower to 30 higher)	‐	50 (1 RCT)	⊕⊝⊝⊝ Very lowa,b,c
Blood gases (PaCO2) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Lung function (PaO2/FiO2 ratio) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Oxygenation index (FiO2% X MPAW/PaO2) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Potential adverse outcomes (episodes of apnoea) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.
See interactive version of this table: https://gdt.gradepro.org/presentations/#/isof/isof_question_revman_web_423282959442933151.

^a We identified significant issues with the randomisation process as well as concealment of allocation
^b A very wide and imprecise confidence intervals (CI), suggesting possible benefit or harm
^c A very small single study

Summary of findings 3. Summary of findings table ‐ Supine compared to good‐lung independent for acute respiratory distress in hospitalised infants and children.

Supine compared to good‐lung independent for acute respiratory distress in hospitalised infants and children
Patient or population: acute respiratory distress in hospitalised infants and children Setting: hospital (paediatric critical care unit) Intervention: supine Comparison: good‐lung independent
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with good‐lung independent	Risk with supine
Mortality (respiratory events) ‐ not reported			‐	‐	No studies reported this outcome
Oxygen saturation (SaO2) ‐ not reported			‐	‐	No studies reported this outcome
PaO 2 follow‐up: range 15 minutes to 45 minutes	The mean paO 2 was 118.14 mmHg	mean 2.78 mmHg lower (28.84 lower to 23.28 higher)	‐	50 (1 RCT)	⊕⊝⊝⊝ Very lowa,b,c
Blood gases (PCO2) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Lung function (PaO2/FiO2 ratio) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Oxygenation index (FiO2% X MPAW/PaO2) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Potential adverse outcomes (episodes of apnoea) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.
See interactive version of this table: https://gdt.gradepro.org/presentations/#/isof/isof_question_revman_web_423283527611744015.

^a We identified significant issues with the randomisation process as well as concealment of allocation
^b Very wide confidence intervals indicating possible benefit or harm
^c Downgraded due to very small single study

Summary of findings 4. Summary of findings table ‐ Good‐lung independent compared to good‐lung dependent positioning for acute respiratory distress in hospitalised infants and children.

Good‐lung independent compared to good‐lung dependent positioning for acute respiratory distress in hospitalised infants and children
Patient or population: acute respiratory distress in hospitalised infants and children Setting: hospital (paediatric critical care unit) Intervention: good‐lung independent Comparison: good‐lung dependent positioning
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with good‐lung dependent positioning	Risk with good‐lung independent
Mortality (respiratory events) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Oxygen saturation (SaO2) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
PaO 2 (cross‐over trial) follow‐up: range 15 minutes to 45 minutes	The mean paO 2 (cross‐over trial) was 111.92 mmHg	MD 6.22 mmHg higher (21.25 lower to 33.69 higher)	‐	50 (1 RCT)	⊕⊝⊝⊝ Very lowa,b,c
Blood gases (PaCO2) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Lung function (PaO2/FiO2 ratio) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Oxygenation index (FiO2% X MPAW/PaO2) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
Potential adverse outcomes (episodes of apnoea) ‐ not reported	‐	‐	‐	‐	‐	No studies reported this outcome
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; MD: mean difference
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.
See interactive version of this table: https://gdt.gradepro.org/presentations/#/isof/isof_question_revman_web_429747819004596191.

^a We identified significant issues due to randomisation and poor allocation concealment
^b Very large confidence intervals suggesting possible benefit or harm
^c Downgraded due to findings from very small single study

Background

Description of the condition

Acute respiratory distress is one of the most frequent causes of hospitalisation and death in young children (Buckmaster 2007; Meurer 2000; Mintegi Raso 2004; Shay 1999), and infants across the world (Ahmed 2004; Caitlin 2008; Chang 2000; Lal 2019; Ritz 2020; Simiyu 2004; Sritipsukho 2007). While there is no official definition of acute respiratory distress (or breathing difficulty), it is clinically recognised as a presentation of one or more of the following signs or symptoms: shortness of breath, wheeze, increased breathing rate, increased heartbeat, increased chest wall retractions, thoracoabdominal asynchrony, pallor, cyanosis, nasal flare, expiratory grunt, and fatigue. Respiratory distress can lead to hypoxemia or hypercapnic respiratory failure, which may require positive pressure ventilation when prone positioning is relevant. Respiratory distress can lead to hypoxaemia with decreased PaO₂ (arterial oxygen pressure), increased PaCO₂ (arterial carbon dioxide pressure), altered neurological status (confusion), and ultimately to respiratory or multiple organ failure (or both), and eventually death (Amigoni 2017; Hazinski 1992a; Hazinski 1992b; Killien 2019). Most infants and young children who develop mild to moderate respiratory distress can be managed at home. However, children with more severe respiratory distress require hospitalisation for treatment, which may include supplemental oxygen, intravenous fluids, intravenous antibiotics, and possibly assisted ventilation.

Description of the intervention

Positioning for therapeutic effect has long been proposed as a means of improving respiratory mechanics and increasing oxygenation (oxygen requirement) in individuals with acute respiratory distress. We define respiratory mechanics as a measure of resistance and elastance, or compliance of the lungs with values of derived indices, such as tidal volume (V_T), respiratory rate, and positive end‐expiratory pressure (PEEP (Bou Jawde 2020; Hess 2014; Silva 2018)). Each index exerts a direct effect on respiratory mechanics when plotted as a function of time or another respiratory index (Hess 2014). Body positioning is a non‐invasive intervention that may augment oxygenation, while avoiding further complications (Bloomfield 2015; Hewitt 2016; Wang 2016). There is no convincing evidence of either benefit or harm from the universal application of prone positioning among adults with hypoxaemia, mechanically ventilated in intensive care units (ICUs (Bloomfield 2015)). However, in children, particularly infants, the risk of injury from oxygen toxicity from mechanical ventilation is greater than in adults, as the lungs are going through a period of high growth and development (Bateman 2000; Hazinski 1992a). Positioning may reduce the need for such interventions, or reduce the required length of time, thereby reducing the associated risk of longer‐term lung damage.

How the intervention might work

Numerous studies on adult and paediatric patients with acute respiratory distress in acute and complex care settings have found that the prone position improves arterial oxygenation compared to the supine position (Bloomfield 2015; Abrams 2020; Cumpstey 2020). Other positions, including lateral (side‐lying) positioning, have also been proposed to assist in maintaining optimal ventilation and oxygenation during episodes of respiratory distress (Hewitt 2016).

Structural differences in the respiratory system are evident in infants and young children when compared with adults (Hazinski 1992a). While supportive airway cartilage, small airway muscles, and the intercostal muscles are not fully developed until school age (Adams 1994), the chest wall of the infant and young child is also much more compliant than the chest wall of an adult (Hazinski 1992a). These differences may lead to a relative increase in the infant's or child's respiratory effort during an episode of respiratory distress, further compromising their ability to maintain adequate ventilation (Adams 1994; Hazinski 1992a).

Why it is important to do this review

specific review of positioning for infants and young children with respiratory distress is warranted, as the structure and respiratory mechanics of the infant and young child differ from those of an adult. Infants and young babies are also at higher risk of deterioration or mortality from acute respiratory distress syndrome (ARDS). It is important to update this review to determine whether prone positioning improves the respiratory management of children with severe, acute respiratory distress. Furthermore, the use of prone positioning for infants is controversial, as it is linked to sudden infant death syndrome (SIDS (Horne 2019)).

Therefore, it is necessary to clarify the benefits and potential risks of body positioning in hospitalised infants and children with acute respiratory distress, to inform evidence‐based clinical practice. There have been four reviews, without meta‐analyses, of positioning in participants with respiratory distress (Ball 1999; Ballout 2017; Curley 1999; Wong 1999). All reviews, except Ballout 2017, which included self‐ventilating infants with apnoea, found that the prone position improved oxygenation in ventilated neonates. However, so far, most of the participants in the reviewed studies are adults. Several of the studies in these reviews included small numbers of children, but excluded neonates.

This review is an update of a systematic review of the effects of positioning on respiratory distress in infants and children (Black 2005; Gillies 2009; Gillies 2012). Each of these reviews found that prone positioning increased oxygenation outcomes, but the majority of data came from trials of neonates. There have now been several Cochrane Reviews that specifically investigated the effects of positioning in neonates (Ballout 2017; Riva‐Fernandez 2016). Although Ballout 2017 did not find evidence that body positioning had any benefits for spontaneously breathing in preterm infants with apnoea, Cochrane Reviews in neonates receiving mechanical ventilation found that the prone position improved oxygenation (Riva‐Fernandez 2016). Because of these reviews in spontaneously breathing and ventilated neonates, we removed neonates from this 2022 update, and focused on infants and children aged between four weeks and 16 years.

Objectives

To compare the effects of different body positions in hospitalised infants and children with acute respiratory distress syndrome aged, between the ages of four weeks and 16 years.

Methods

Criteria for considering studies for this review

Types of studies

We included randomised controlled trials (RCTs) or quasi‐RCTs, comparing two or more positions in the management of infants and children hospitalised with acute respiratory distress.

Types of participants

 

Hospitalised infants older than four weeks, and children up to 16 years of age, with a primary or secondary diagnosis of acute respiratory distress, or with an acute exacerbation of a chronic respiratory illness. The studies included the following conditions in infants and children.

1. Acute respiratory failure

2. Acute respiratory distress syndrome (ARDS)

3. Acute lung injury

4. Acute respiratory distress due to lower respiratory tract infections: bronchiolitis, pneumonia (bacterial, viral, and atypical)

5. Bronchitis, legionella, whooping cough; chronic neonatal lung disease (bronchopulmonary dysplasia, respiratory distress syndrome, hyaline membrane disease)

6. Upper respiratory tract infections, including croup, epiglottitis (laryngotracheobronchitis)

7. Laryngeal infections; acute episodes of chronic suppurative lung diseases, including bronchiectasis and cystic fibrosis; inflammatory respiratory conditions, such as asthma

8. Congenital malformations of the bronchi, lungs, diaphragm, and rib cage

9. Disorders of the pleura (for example pneumothorax, pleural effusion)

Types of interventions

Body positions used for the management of infants and children with acute respiratory distress included the following.

1. Sitting − erect sitting, forward‐leaning sitting, and non‐erect sitting

2. Prone − prone abdomen free, prone abdomen restricted, semi‐prone, quarter‐prone, horizontal (flat), and head elevated

3. Lateral recumbent or side‐lying position − horizontal (flat) and head elevated (this position can be good‐lung dependent, where the person lies on the side of the healthy lung; or good‐lung independent, where the person lies on the side opposite to the healthy lung).

4. Supine − horizontal (flat) and head elevated

5. Kinetic positioning − continuous postural therapy (usually with an automated bed)

6. Body tilting

Types of outcome measures

A range of outcomes on positioning for infants and young children with ARDS was assessed in the included studies. The outcomes measured and reported also varied across the trials. Oxygenation outcomes included: arterial oxygen saturation, partial pressure of oxygen and carbon dioxide in arterial blood, lung function, and oxygenation index. Ventilatory outcomes included: tidal volume, minute volume, dynamic lung compliance, inspiratory resistance, expiratory resistance, total pulmonary resistance, respiratory rate, work of breathing, and laboured breathing index. Other outcomes were heart rate, oesophageal pressure, and adverse events. These are listed below, with their definition and significance.

Primary outcomes

1. Mortality: respiratory events

2. Oxygen saturation: arterial oxygen saturation (SaO₂)

3. Blood gases: partial pressure of carbon dioxide in arterial blood (PaCO₂) and partial pressure of oxygen in arterial blood (PaO₂), all in mmHg

4. Lung function or P/F ratio (PaO₂/FiO₂ ratio): ratio of arterial oxygen partial pressure (PaO₂ in mmHg) to the fraction of inspired oxygen (FiO₂ expressed as a fraction, not a percentage). It is a clinical indicator of hypoxemia that suggests the possibility of ARDS from a sudden state of lung insufficiency. The severity of ARDS is measured by the PaO₂/FiO₂ ratio, which ranges from 200 to 300 for mild, 100 to 200 for moderate, and 0 to 100 for severe hypoxemia (ARDS Definition Task Force 2012).

5. Oxygenation index (FiO₂% X M_PAW/PaO₂): used in paediatrics to determine the breathing capacity, and to predict the future outcome or assessment for potential extracorporeal membrane oxygenation (ECMO (Trachsel 2005)). An oxygenation index < 25% predicts a good outcome, 25% to 40% indicates signs of mortality, and children with values > 40% should be considered for ECMO (Kathirgamanathan 2009).

6. Episodes of apnoea in non‐ventilated children

Secondary outcomes

1. Respiratory mechanics: measure of resistance and elastance, or compliance of the lungs with values of derived indices, such as tidal volume (V_T), respiratory rate, and positive end‐expiratory pressure (PEEP)

2. Heart rate

3. Per cent inspired oxygen received: FiO₂; standardised protocol

4. Duration of supplemental oxygenation: standardised protocol

5. Intensive care unit (ICU) admission: standardised protocol

6. Length of hospital stay

7. Mortality: all causes

8. Haemodynamic parameters

9. Ventilatory parameters

Potential adverse outcomes

1. Accidental removal and compression of intravenous lines, endotracheal tube (or both)

2. Hypercapnia

3. Facial oedema

4. Pressure ulcer

5. Cutaneous damage to the chest wall

6. Contractures of the hip and shoulder

7. Raised intra‐ocular pressure, deterioration in visual acuity

8. Gastrointestinal event

9. Any other adverse events reported by study authors

Search methods for identification of studies

Electronic searches

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2021, Issue 7) in the Cochrane Library, which contains the Acute Respiratory Infections Group's Specialised Register, MEDLINE (January 2004 to July week 4, 2021), Embase (January 2004 to July 2021), and CINAHL (January 2004 to July 2021).

We searched CENTRAL and MEDLINE using the search strategy described in Appendix 1. We combined the MEDLINE search terms with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE, sensitivity‐ and precision‐maximising version (2008 revision); Ovid format (Lefebvre 2021). We adapted the search strategy to search Embase (Appendix 2), and CINAHL (Appendix 3). We used no language or publication restrictions. Previous searches are detailed in Appendix 4.

Searching other resources

We searched the trials registries, World Health Organization International Clinical Trials Registry Platform (apps.who.int/trialsearch) and US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (www.clinicaltrials.gov) for completed and ongoing trials up to July 2021. We made all reasonable efforts to contact recognised experts in the fields of respiratory and intensive care medicine to obtain any additional trials, where applicable. We sent emails to primary or corresponding authors of potentially eligible studies and used the information provided if we got a reply. We manually searched the reference lists of included and excluded trials to identify any other published or unpublished works relevant to the review topic.

Data collection and analysis

Selection of studies

Initially, two review authors (JYT, APB) independently examined all potentially relevant citations using Covidence and retrieved the full text of articles that met the selection criteria in Review Manager 2020. Two review authors (JYT, APB) independently compared each article against the selection criteria to determine which articles to select for data extraction. During a subsequent update, due to expired search dates, two review authors (DAN, LV) independently examined all potentially relevant citations using Covidence, and retrieved the full text of articles that met the inclusion criteria in Review Manager 2020. We resolved any differences either by referral to a topic expert, consensus with a co‐author, or both. To reduce the risk of publication bias, there were no language restrictions.

Data extraction and management

We used a standardised data extraction form. Two review authors (JYT, APB) independently extracted data from each study, without blinding to authorship or journal publication. We resolved differences either by consensus or by referral to a contributor with topic expertise. When there were missing data, or further information was required, we contacted trial authors to obtain the required information. We extracted data from graphs where necessary. When duplicate publication occurred, the publication with the most data was the primary reference for the review. We kept and managed records of all articles identified from the search strategies, included and excluded, using a reference management system (Covidence).

Data extraction included the following categories.

1. Method of allocation

2. Concealment of allocation

3. Country and setting where the study was performed

4. Participant details

5. Inclusion and exclusion criteria

6. Details of intervention

7. Outcomes measured

8. Confounders

9. Duration of study and frequency of measurements

10. Numbers enrolled and completed in each group

11. Baseline characteristics

12. Results for each group

Assessment of risk of bias in included studies

Three review authors (JYT, APB, MK) independently assessed the quality of the trials to be included, without blinding to authorship or journal of publication. We assessed primary outcomes (where available) or secondary outcomes of parallel trials and cross‐over trials using the Cochrane RoB 2 tool (Sterne 2019). We also evaluated the risk of bias in the trials based on blinding to intervention, outcome measurement and completeness of follow‐up. We resolved differences in the allocation of trials into quality categories either by consensus or by referral to a third person with content expertise.

Measures of treatment effect

For binary outcomes, we calculated the odds ratio (OR) and 95% confidence interval (CI). We calculated the mean difference (MD) and 95% confidence interval (CI), using a fixed‐effect model for continuous outcomes. If we found significant heterogeneity (I² statistic > 50%), we used a random‐effects model (Assessment of heterogeneity). For the other comparisons, we extracted data as median and interquartile range in Table 5, or mean and standard deviation in Table 6 and Table 7.

1. Prone versus supine positioning (median and range data).

Study	Outcome	Supine (N)	Supine (median)	Supine (IQ range*)	Prone (N)	Prone (median)	Prone (IQ range*)
Baudin 2019	TcPCO2 (kPA)	14	6.5	* 6.1 to 6.8	14	6.9	* 6.1 to 7.7
Baudin 2019	FiO2 (%)	14	30	* 25 to 35	14	27	* 25 to 30
Baudin 2019	SpO2 (%)	14	97.5	* 95 to 99	14	96.5	* 94 to 98
Baudin 2019	Heart rate (beats/min)	14	159	* 146 to 164	14	156	* 144 to 163
Curley 2005	Minute ventilation (minutes)	42	1.6	* 1.0 to 3.2	42	1.6	0.6 to 2.8

* Interquartile range

2. Supine compared to good‐lung dependent (mean and SD data).

Study	Outcome	Participants (N)	Supine (mean)	Supine (SD)	Good‐lung dependent lung (mean)	Good‐lung dependent lung (SD)
Polacek 1992	PO2	25	115.36	45.28	111.92	50.42

Cross‐over trial with 13 participants in the intervention arm and 12 in the control arm

SD = standard deviation

3. Supine compared to good‐lung independent (mean and SD data).

Study	Outcome	Participants (N)	Supine (mean)	Supine (SD)	Good‐lung independent lung (mean)	Good‐lung independent lung (SD)
Polacek 1992	PO2	25	115.36	45.28	118.14	48.67

Cross‐over trial with 12 participants in the intervention arm and 13 in the control arm

SD = standard deviation

Unit of analysis issues

Ideally, we would have used the results from paired analyses from the cross‐over trials. However, we included data from the first period only, as the cross‐over studies only reported data from the first period. Therefore, to maintain the quality of the current study, we followed the recommendations of Elbourne 2002 that state, "the results of two or more cross‐over trials might be combined, but with this pooled result kept separate from the data from  parallel‐group trials". We could not correct data for paired analysis in the meta‐analysis of cross‐over trials because of incomplete information, which may mean that we over‐estimated the pooled variance. Therefore, significant effects across groups may be less apparent in the meta‐analyses of cross‐over trials compared to the meta‐analyses of parallel‐group studies.

Dealing with missing data

We analysed data, as planned, on an intention‐to‐treat (ITT) basis. However, we did not perform a sensitivity analysis for parallel randomised trials or cross‐over trials, as data for this analysis were not reported.

Assessment of heterogeneity

We interpreted a Mantel‐Haenszel Chi² value of less than 0.10, or an I² statistic greater than 50%, or both, as significant heterogeneity. If heterogeneity was significant, we used a random‐effects model.

Assessment of reporting biases

Had there been 10 or more parallel trials reporting the same primary outcome, we would have generated a funnel plot (trial effect against trial size) to investigate the possibility of publication bias, but there were not enough data to do this.

Data synthesis

We undertook meta‐analyses where similar and meaningful combinations of participants with the same treatments and comparison groups were reported under similar clinical timings. We calculated the pooled OR and corresponding 95% CI for binary outcomes using a fixed‐effect model. We calculated the mean difference (MD) and 95% CI interval for meta‐analysis of continuous outcomes using a fixed‐effect model. If we found significant heterogeneity, we used a random‐effects model (Assessment of heterogeneity).

Subgroup analysis and investigation of heterogeneity

We considered a subgroup analysis to compare findings in different age groups, but there were not enough study data.

The pathophysiology of acute respiratory distress varies substantially. Therefore, we proposed to undertake a subgroup analysis based on the reported cause (and related pathophysiology) of respiratory distress.

We also proposed to include a subgroup analysis of the following age categories.

1. Infants (28 days to 12 months)

2. Toddlers and young children (12 months to 5 years)

3. School‐age children (5 to 16 years)

As there may be greater scope for non‐ventilated participants to benefit from therapeutic body positioning, we also planned subgroup analysis of ventilated versus non‐ventilated children. We planned a subgroup analysis based on the temporal parameters of the positioning, if appropriate.

Sensitivity analysis

We had planned to undertake a sensitivity analysis based on the level of potential allocation bias. However, there were not enough data to do this.

Summary of findings and assessment of the certainty of the evidence

We created four summary of findings tables for the following outcomes: mortality (respiratory events), oxygen saturation (SaO₂), blood gases (PaCO₂ and PaO₂), PaO₂/FiO₂ ratio, oxygenation index (FiO₂% X M_PAW/ PaO₂), episodes of apnoea, and adverse outcomes (extubation or apnoea). See Table 1; Table 2; Table 3; Table 4.

We used the five GRADE considerations (study limitations, consistency of effect, imprecision, indirectness, and publication bias) to assess the quality of evidence as it related to the studies that contributed data to the meta‐analyses for the prespecified outcomes (Atkins 2004). We used methods and recommendations described in Section 8.5 and Chapter 12 of the Cochrane Handbook for Systematic Reviews of Interventions, and GRADEproGDT software (GRADEpro GDT; Higgins 2021). We justified all decisions to down‐ or upgrade the quality of evidence in footnotes, and made comments to aid readers’ understanding of the review where necessary.

Results

Description of studies

See Characteristics of included studies and Characteristics of excluded studies tables.

Results of the search

Following the original search, the first, second, and final updates that searched electronic databases up to July 2021, we identified 4798 unique records with 425 duplicates. We obtained 123 citations reporting 119 studies, commentaries, and reviews in full text based on the title and abstract. We excluded 116 studies (115 citations) following data extraction and included 6 studies (7 records). Citation screening identified one additional study after the final update for inclusion (Baudin 2019).

Included studies

Overall, we extracted data from six trials. Four were randomised controlled cross‐over trials (Baudin 2019; Kornecki 2001; Levene 1990; Polacek 1992). The remaining two trials were parallel randomised trials (Curley 2005; Ibrahim 2007).

Baudin 2019 was funded by a grant from the Fonds de recherche en santé du Québec. Curley 2005 was funded by the NIH/NINR. Levene 1990 was funded by the North East Thames Regional Health Authority. Ibrahim 2007 was supported by Al‐Noor specialist hospital‐KSA. Kornecki 2001 was supported by the Department of Critical Care Medicine, Division of Respiratory Medicine, Hospital for Sick Children, University of Toronto, Toronto, Ontario. Polacek 1992 was supported by the Children's Mercy Hospital, Kansas City, Missouri.

There was a total of 198 participants. Thirteen (7.1%) of the participants were infants, aged between four weeks and 12 months (Levene 1990). The remaining 171 participants were aged one month to 16 years (Curley 2005; Ibrahim 2007; Kornecki 2001; Polacek 1992), all but 15 of whom were mechanically ventilated (Polacek 1992).

The inclusion and exclusion criteria were not uniform across included trials. One study did not list any exclusion criteria, but excluded two children from the prone versus supine comparison because physical restrictions prevented them from being placed prone (Kornecki 2001). Curley 2005 and Ibrahim 2007 had extensive exclusion criteria, which included cardiac, respiratory, and neurological abnormalities.

The interventions included prone versus supine (Baudin 2019; Curley 2005; Ibrahim 2007; Kornecki 2001; Levene 1990); supine versus prone versus lateral; and right lateral versus left lateral (Polacek 1992).

The trial times also varied greatly, ranging from 15 minutes after a 15‐minute settling‐in period in Polacek 1992, to a median of 20 hours over a four‐day period in the studies by Curley 2005 and Ibrahim 2007. The outcomes reported across trials were arterial oxygen saturation (SaO₂), transcutaneous oxygen pressure (PO₂), transcutaneous carbon dioxide pressure (PCO₂), lung function or P/F ratio, oxygenation index, tidal volume (V_T), heart rate, respiratory rate, and adverse events.

Excluded studies

We excluded 27 of the 49 citations selected for full‐text review in the original review. These citations did not meet the selection criteria during a previous update (Gillies 2012) and remained excluded for this update. In this update, we excluded 36 studies as they did not meet the selection criteria. In 16 studies, the population was ineligible; eight used the wrong population (Akatsuka 2018; Jang 2020; Li Bassi 2017a; Li Bassi 2017b; Li Bassi 2017c; Li Bassi 2017; Najafi 2017; Panigada 2017a), seven evaluated the intervention among an adult population (Anonymous 2005; Ayzac 2016; Hassankhani 2017; Li 2018; Pelosi 2001; Thompson 2013; Trikha 2013), and one evaluated a neonatal population (Pourazar 2018). Out of 10 studies, two used observational study designs (Curley 2000; Murdoch 1994), and eight studies used inappropriate study designs (Baston 2019; Brzęk 2019; Casado‐Flores 2002; Du 2018; Kamo 2018; Lee 2018; Leger 2017; Munshi 2017). Five studies were literature reviews (Bourenne 2018; Dalmedico 2017; Gattinoni 2018; Guervilly 2019; Johnson 2017), two were systematic reviews (Teng 2018; Yue 2017), and one was a commentary (Kavanagh 2005). One study evaluated the wrong intervention (Li 2018), and one reported the wrong outcomes (Yonis 2017). One study was a conference presentation (Panigada 2017b), and one was a duplicate record for a study already considered for inclusion (Panigada 2017a).

Risk of bias in included studies

The overall risk of bias for primary or main outcomes as reported by study authors is summarised in Figure 1. See Characteristics of included studies.

1.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study

Allocation

Only two included trials provided an adequate description of the random sequence generation and concealment of allocation (Baudin 2019; Curley 2005). We judged both trials at low risk of allocation bias. We considered all other trials at unclear risk of bias because sequence generation and allocation concealment were not described. This raised concerns about selection bias.

Blinding

We considered all trials at unclear risk or posing some concerns, because there was an inadequate description of the blinding process. However, we considered the risk of unblinded observers biasing the outcome unlikely, because objective outcomes were used.

Incomplete outcome data

We considered four trials as unclear risk of bias due to missing outcomes, as there was some loss to follow‐up (1/102)  in Curley 2005, Ibrahim 2007, and Kornecki 2001, though minimal (2/16) in the study by Baudin 2019. However, we considered Levene 1990 at high risk of bias due to missing outcomes. Levene 1990 did not collect data from nine infants as the babies did not sleep or wake up during study time. There appeared to be complete follow‐up in Polacek 1992, which we considered at low risk of bias due to missing outcomes.

Selective reporting

We identified selective reporting of data for lung mechanics by Kornecki 2001. While the authors reported no differences between interventions, the data justifying this report were not shown.

Other potential sources of bias

A potential source of bias was the inclusion of four randomised controlled cross‐over trials (Baudin 2019; Kornecki 2001; Levene 1990; Polacek 1992). However, we did not identify bias arising from period or carry‐over effects in these studies. Furthermore, we analysed these studies using data from the first period only.

Effects of interventions

See: Table 1; Table 2; Table 3; Table 4

Comparison 1: Prone versus supine positioning

Primary outcomes

1. Mortality: respiratory events

None of the studies included in this comparison reported data for this primary outcome.

2. Oxygen saturation (SaO₂)

One trial reported oxygen saturation for prone versus supine positioning (Levene 1990). There was an inconclusive finding between the prone and supine groups in the SaO₂ (mean difference (MD) 0.40 mmHg, 95% confidence interval (CI) ‐1.22 to 2.66; 30 participants; very low certainty evidence). The evidence is very uncertain about the change in oxygen saturation in the upper respiratory tract infection (MD ‐0.50 mmHg, 95% CI ‐2.58 to 1.58; 13 participants) and lower respiratory tract infection (MD 1.80, 95% CI ‐0.78 to 4.38; 17 participants; fixed‐effect; Analysis 1.1).

1.1. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 1: SaO₂

3. Blood gases (PaCO₂, PaO₂)

Curley 2005 reported PaCO₂ and PaO₂ for prone versus supine positioning in 99 participants. There was no conclusive finding between the prone and supine groups in the PaCO₂ (MD 3.0 mmHg, 95% CI ‐1.93 to 7.93; 99 participants; low certainty evidence; fixed‐effect; Analysis 1.2). There were also inconclusive results between the prone and supine groups in the PaO₂ (MD 2 mmHg, 95% CI ‐5.29 to 9.29; 99 participants; fixed‐effect; Analysis 1.3).

1.2. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 2: PaCO₂

1.3. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 3: PaO₂

4. Lung function (PaO₂/FiO₂)

Two trials measured lung function (Curley 2005; Ibrahim 2007).

There were no conclusive findings in lung function or PaO₂/FiO₂ (MD 28.16 mmHg, 95% CI ‐9.92 to 66.24; 2 trials, 121 participants; very low certainty evidence; random‐effects; Analysis 1.4).

1.4. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 4: PaO₂/FiO₂ ratio

5. Oxygenation index (FiO₂% X M_PAW/PaO₂)

Two parallel trials (Curley 2005; Ibrahim 2007) and one cross‐over trial (Kornecki 2001) reported oxygenation index for prone versus supine positioning. The oxygenation index was improved in the prone group (MD ‐2.42, 95% CI ‐3.60 to ‐1.25; 2 trials, 121 participants; very low certainty evidence; I² = 0%; fixed‐effect; Analysis 1.5). This was largely due to the greater weighting given to the smaller study by Ibrahim 2007, which reported small standard deviations. Placing participants in the prone position also improved the oxygenation index in the study by Kornecki 2001 (MD ‐8.13, 95% CI ‐15.01 to ‐1.25; 10 participants; fixed‐effect; Analysis 1.6).

1.5. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 5: Oxygenation index (parallel trials)

1.6. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 6: Oxygenation index (cross‐over trial)

Oxygenation index by time

Kornecki 2001 also measured the oxygenation index as an outcome over time. Measurements were taken at 0.5 hours (MD ‐0.83, 95% CI ‐8.04 to 6.38), 2 hours (MD ‐2.08, 95% CI ‐8.61 to 4.45), 4 hours (MD ‐4.20, 95% CI ‐9.37 to 0.97), 6 hours (MD ‐5.13, 95% CI ‐10.13 to ‐0.13), 8 hours (MD ‐6.89, 95% CI ‐12.93 to ‐0.85), and 12 hours (MD ‐8.13, 95% CI ‐15.01 to ‐1.25). Measurements were inconclusive between prone and supine positioning until the six‐hour measurement. However, this improvement continued and was maintained for up to 12 hours; fixed‐effect; Analysis 1.6.

6. Episodes of apnoea

None of the studies included in this comparison reported data for this primary outcome.

Secondary outcomes

1. Respiratory mechanics (as defined by study authors)

Two trials assessed respiratory mechanics for prone versus supine positioning (Curley 2005; Kornecki 2001). 

There was an apparent decrease in tidal volume between the prone and supine groups in the study by Curley 2005 (MD ‐0.60, 95% CI ‐1.05 to ‐0.15; 84 participants; fixed‐effects; Analysis 1.7). 

1.7. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 7: Tidal volume

Kornecki 2001 did not report the collective data for respiratory mechanics but reported compliance, positive end‐expiratory pressure (PEEP), and resistance instead. There were inconclusive results between the prone and supine positions in respiratory compliance (MD 0.07, 95% CI ‐0.10 to 0.24; 10 participants; fixed‐effect; Analysis 1.8), a change in PEEP (MD ‐0.70 cm H₂O, 95% CI ‐2.72 to 1.32; 20 participants; fixed‐effect; Analysis 1.9), and resistance (MD ‐0.00, 95% CI ‐0.05 to 0.04; 20 participants; fixed‐effect; Analysis 1.10).

1.8. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 8: Respiratory compliance

1.9. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 9: Positive end‐expiratory pressure (PEEP)

1.10. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 10: Respiratory resistance

2. Heart rate

Baudin 2019 assessed heart rate for prone versus supine positioning. The authors reported no significant difference in heart rate between the prone and the supine position (Table 5).

3. Per cent inspired oxygen received (FiO₂)

Baudin 2019 also assessed per cent inspired oxygen for prone versus supine positioning. The authors reported no significant difference in FiO₂ between the prone and the supine position (Table 5).

None of the included trials evaluated any of the other secondary outcomes or measured the length of intensive care unit or hospital stay.

Potential adverse outcomes

Curley 2005 reported extubations due to adverse events, obstructions of the endotracheal tube, pressure ulcers, and hypercapnia (high levels of arterial carbon dioxide). There were no conclusive findings for groups for extubation (odds ratio (OR) 0.57, 95% CI 0.13 to 2.54; 1 trial; 102 participants; very low certainty evidence), and the obstruction of the endotracheal tubes (OR 5.20, 95% CI 0.24 to 111.09; 1 trial; 102 participants; fixed‐effect; Analysis 1.11). The authors also found no conclusive evidence of a difference between groups for pressure ulcers (OR 1.00, 95% CI 0.41 to 2.44; 1 trial; 102 participants) and hypercapnia (OR 3.06, 95% CI 0.12 to 76.88; 1 trial; 102 participants; fixed‐effect; Analysis 1.11).

1.11. Analysis.

Comparison 1: Prone versus supine positioning, Outcome 11: Potential adverse outcomes

None of the included trials reported data for cutaneous damage to the chest wall. 

Comparison 2: Supine versus good‐lung dependent positioning

Primary outcomes

1. Mortality: respiratory events

None of the included trials in this comparison reported data for this primary outcome.

2. Oxygenation saturation (SaO₂)

None of the included trials in this comparison reported data for this primary outcome.

3. Blood gases (PaCO_2, PO₂)

Polacek 1992 compared the PaO₂ in the supine position to the good‐lung independent position. There was an inconclusive result that PaO₂ was different between supine position and good‐lung independent (MD 3.44 mmHg, 95% CI ‐23.12 to 30.00; 1 study, 25 participants; very low certainty evidence; Table 6; fixed‐effect; Analysis 2.1).

2.1. Analysis.

Comparison 2: Supine versus good‐lung dependent positioning, Outcome 1: PaO₂ (cross‐over trial)

4. Lung function (PaO₂/FiO₂)

None of the included trials in this comparison reported data for this primary outcome.

5. Oxygenation index (FiO₂% X M_PAW/PaO₂)

None of the included trials in this comparison reported data for this primary outcome.

6. Episodes of apnoea

None of the included trials in this comparison reported data for this primary outcome.

Secondary outcomes

None of the included trials evaluated any secondary outcomes or measured the intensive care unit, or hospital length stay.

Potential adverse outcomes

For this comparison, no data were reported for any of the potential adverse outcomes.

Subgroup analysis

We intended to conduct subgroup analyses on ventilated versus non‐ventilated subgroups based on age groups, but there were inadequate data.

Sensitivity analysis

We had planned to conduct a sensitivity analysis based on the risk of bias assessment. However, this was not possible due to inadequate data.

Comparison 3: Supine versus good‐lung independent positioning

Primary outcomes

1. Mortality: respiratory events

None of the included trials in this comparison reported data for this primary outcome.

2. Oxygenation saturation (SaO₂)

None of the included trials in this comparison reported data for this primary outcome.

3. Blood gases (PaCO_2, PO₂)

Polacek 1992 compared the PaO₂ in the supine position with the good‐lung independent positioning. There was no conclusive result between positions for the PaO₂ (MD ‐2.78 mmHg, 95% CI ‐28.84 to 23.28; 1 study, 25 participants; very low certainty evidence; fixed effects; Analysis 3.1; Table 7).

3.1. Analysis.

Comparison 3: Supine versus good‐lung independent positioning, Outcome 1: PaO ₂ (cross‐over trial)

4. Lung function (PaO₂/FiO₂)

None of the included trials in this comparison reported data for this primary outcome.

5. Oxygenation index (FiO₂% X M_PAW/PaO₂)

None of the studies included in this comparison reported data for this primary outcome.

6. Episodes of apnoea

None of the included trials in this comparison reported data for this primary outcome.

Secondary outcomes

None of the included trials evaluated any secondary outcomes or measured the length of intensive care unit or hospital stay.

Potential adverse outcomes

None of the included trials in this comparison reported data for any potential adverse outcomes.

Comparison 4: Good‐lung independent positioning versus good‐lung dependent positioning

Primary outcomes

1. Mortality: respiratory events

None of the included trials in this comparison reported data for this primary outcome.

2. Oxygenation saturation (SaO₂)

None of the included trials in this comparison reported data for this primary outcome.

3. Blood gases (PaCO_2, PO₂)

Polacek 1992 compared the PaO₂ in the good‐lung independent position with the good‐lung dependent positioning. There was no conclusive finding between positions for the PaO₂ (MD 6.22, 95% CI ‐21.25 to 33.69; 1 study, 25 participants; very low certainty evidence; fixed‐effect; Analysis 4.1; Table 8).

4.1. Analysis.

Comparison 4: Good‐lung independent versus good‐lung dependent positioning, Outcome 1: PaO₂ (cross‐over trial)

4. Good‐lung independent compared to good‐lung dependent (mean and SD data).

Study	Outcome	Participants (N)	Good‐lung independent (mean)	Good‐lung independent lung (SD)	Good‐lung dependent (mean)	Good‐lung dependent lung (SD)
Polacek 1992	PO2	25	118.14	48.67	111.92	50.42

Cross‐over trial with 12 participants in the intervention arm and 13 in the control arm

SD = standard deviation

4. Lung function (PaO₂/FiO₂)

None of the included trials in this comparison reported data for this primary outcome.

5. Oxygenation index (FiO₂% X M_PAW/PaO₂)

None of the included trials in this comparison reported data for this primary outcome.

6. Episodes of apnoea

None of the included trials in this comparison reported data for this primary outcome.

Secondary outcomes

None of the included trials evaluated any secondary outcomes or measured intensive care unit length of stay or hospital stay.

Potential adverse outcomes

None of the included trials in this comparison reported data for any potential adverse outcomes.

Discussion

Overall, there seems to be little, and low certainty evidence to suggest a positive impact of positioning and mechanical ventilation on pulmonary physiology in hospitalised infants and children. An understanding of how haemodynamic stability and respiratory mechanics vary with changes in oxygenation and ventilatory outcomes becomes vital for optimal gas exchange and alveolar perfusion. Although a clear relationship between deficiency in a single oxygenation parameter and hypoxemia exists, respiratory mechanics vary due to changes in one ventilatory parameter against another, or as a function of time. 

In the current review, ventilatory outcomes were analysed by Curley 2005 and Kornecki 2001. While data for lung mechanics were not shown by Kornecki 2001, we separately reported study results of the indices predicting respiratory mechanics. However, results should be interpreted with caution, as to whether parameters represent a causal relationship with the observed change.

Prolonged ventilation with higher tidal volumes and airway pressures may exacerbate ventilator‐associated lung injury for patients in prone positions (Henderson 2014). While Curley 2005 investigated the use of low tidal volumes during prolonged periods of prone ventilation, the observed decrease in tidal volume allows for an even distribution of oxygen in the alveoli. One of the major complications associated with prone positioning is reduced tidal volume, with a concomitant decrease in the amount of oxygen delivered in or out of the lungs. However, the clinical benefits lie in its ability to reduce or prevent mechanical lung injury from alveolar distension and trauma. Likewise, there is a concomitant increase in oxygenation index during prone positioning, with more homogenous lung ventilation and perfusion. Guérin 2013 also reported improved oxygenation and reduced ventilator days as a complementary benefit of prone positioning in adults with acute respiratory distress syndrome. However, the current evidence is insufficient to determine the relationship between low tidal volume and reduced ventilator days in infants and children on prone ventilation.

It is also important to bear in mind the possible bias introduced by the included cross‐over studies. As included cross‐over designs only reported data from first periods, there was a lack of information to ascertain how issues regarding carry‐over effects were resolved by the authors. As paired analysis was not possible, we reported data from cross‐over trials as if they were parallel trials, but did not combine them with the parallel randomised trials. Therefore, these results need to be interpreted with caution. The inclusion of the study by Baudin 2019 introduced bias to the review, as study results were reported as interquartile ranges, indicative of skewed data. However, it would be inappropriate to remove the Baudin 2019 trial, as this could also introduce selection bias. Therefore, we reported the results for heart rate and FiO₂ narratively.

Summary of main results

There appears to be low certainty evidence that there may be a positive effect of positioning on improving oxygenation in children with ARDS, who are mechanically ventilated. However, these results were limited by insufficient data from the included trials. There were also limited data to make any conclusions about adverse effects.

While there were few studies that met the inclusion criteria of this updated review, the included cross‐over trials reported data from only the first periods, which may have introduced a selection bias of the corresponding analyses. Although a particular concern with cross‐over designs is the risk of a carryover effect, the trial authors did clarify why they analysed data from the first period only. Another potential source of bias acknowledged in the study by Kornecki 2001 was incomplete outcome data and attrition bias as the trial authors also did not account for one participant when analysing respiratory mechanics. Baudin 2019 reported data as means and interquartile ranges (IQR). While the use of IQR depicts a high probability of bias in the reported data, calculating SD from interquartile range was not feasible, and results were reported narratively. While we considered the risk of selection, attrition, and detection bias to be high in the majority of the included studies, the trials did not describe how these potential biases were addressed. Therefore, there may still be other risks of bias in these trials.

Overall completeness and applicability of evidence

Given the limited amount of data and the possibility of publication bias, we were unable to draw any conclusions about the relative benefits and harms of any position in infants and children who have acute respiratory distress. No data were reported for clinically meaningful outcomes, such as mortality, morbidity, and recovery variables.

Although, we proposed to undertake a subgroup analysis based on age, the reported cause, and related pathophysiology of respiratory distress, we could not evaluate inconsistency in the result due to variation in the pathophysiology of acute respiratory distress. The only data available for subgroups came from one small trial by Levene 1990, which reported data from infants with upper and lower respiratory tract infections in the prone and supine positions.

Studies conducted amongst young infants face technical difficulties during outcome measurements. Hence, they are usually done when the infants are asleep, and are of short duration. For example, 2/12 participants were not included in one trial because they could not be placed in a prone position due to physical restrictions (Kornecki 2001). In the trial by Levene 1990, 9/39 infants did not go to sleep or woke when moved; hence did not contribute data to the review.

Quality of the evidence

Small participant numbers and short study times are major limitations to the conclusions drawn from this review. There was very low certainty evidence on the effects on oxygen saturation, lung function (PaO₂/FiO₂ ratio), oxygenation index (FiO₂% X M_PAW/ PaO₂), tidal volume, extubation, obstructions of the endotracheal tube, pressure ulcers, and hypercapnia with prone positioning in both the parallel trials and cross‐over studies.

There was very low certainty evidence when supine positioning was compared to good‐lung dependent and independent positioning. There was very low certainty evidence when good‐lung independent positions and good‐lung dependent positions were compared. 

The majority of studies reported data from fewer than 50 infants or children, with the number of participants ranging from 10 (Kornecki 2001) to 102 (Curley 2005). Only two trials used random sequence generation during the conduct of their trials (Baudin 2019; Curley 2005). As most of the trials included in this review were of short duration, it was not possible to establish whether any beneficial or adverse effects of positioning became clinically meaningful over longer periods. Only three trials collected data for more than an hour. Three reported outcomes from 2 to 24 hours (Curley 2005; Ibrahim 2007; Kornecki 2001), and no trial reported data for more than 24 hours. The study by Kornecki 2001 highlights the importance of collecting data for longer periods. While there was no difference between the prone and supine positions until the sixth hour, oxygenation appears to have steadily increased up to 12 hours.

Potential biases in the review process

For the primary objective, we compared studies amongst hospitalised infants and children with acute respiratory distress syndrome aged between four weeks and 16 years, to minimise potential biases in interpreting the intervention effects, by following Cochrane recommendations (Higgins 2011).  We conducted comprehensive searches without limiting the searches to a specific language. Two review authors independently assessed study eligibility, extracted data, and assessed the risk of bias for each included study. A third reviewer (with clinical expertise) adjudicated when there were discrepancies. 

However, there is the possibility that some studies available through the grey literature or unpublished may have been missed. Also, we used the updated version of the RoB 2 tool to assess the limitations of some of the source's biases in included studies (Sterne 2019). Since this version of the review is an update, this post hoc decision may have introduced some bias, but improved the comparability of our findings with current research.

Agreements and disagreements with other studies or reviews

The findings from this review show that short‐ and medium‐term prone positioning may be beneficial in improving oxygenation and ventilation in acutely respiratory‐distressed ventilated infants or children. Riva‐Fernandez 2016 concluded that prone position in ventilated preterm neonates improved oxygenation in the short term.

Similarly, reviews of positioning for respiratory‐distressed, ventilated adult participants have also concluded that prone positioning helped improve oxygenation in the short term (Ball 1999; Curley 1999; Munshi 2017; Wong 1999). However, the evidence is inconclusive for mortality and adverse events, which were higher among participants placed in prone positions in Bloomfield 2015 and Munshi 2017.

Authors' conclusions

Implications for practice.

Prone positioning may offer some advantage over other positions in improved oxygenation and lung protection for ventilated infants or children hospitalised with acute respiratory distress. However, the benefits of prone positioning cannot be extrapolated to non‐hospitalised infants and children with respiratory distress, due to the increased risk of sudden infant death syndrome (SIDS) with prone positioning. Due to the increased risk of lung injury associated with artificial ventilation, it is further recommended that hospitalised infants placed in the prone position be closely monitored, due to the increased risk of hypoxia associated with acute respiratory distress.

At present, there is insufficient evidence to make solid recommendations regarding the preferred position to support hospitalised infants and children with acute respiratory distress. 

Implications for research.

Large, international, multicentre, randomised controlled trials are required to better assess the effect of positioning respiratory‐distressed infants and children in the prone position. Future studies should also collect clinically meaningful data, such as mortality, morbidity, recovery variables, and adverse effects. Trials also need to determine the optimal frequency and timing of the prone position to gain maximal sustained benefits over a longer duration. As most identified studies reported data from children, future studies are needed to determine whether the prone position is also effective for infants, as well as the effect on their quality of life. In addition, to investigate whether findings are consistent across a range of participants, future trials should report separate data for subgroups of infants and children based on the age group, the causes of acute respiratory distress, and whether they are mechanically ventilated. Further research on the effectiveness of other positions for infants and children with acute respiratory distress is also needed.

What's new

Date	Event	Description
26 July 2021	New citation required but conclusions have not changed	Our conclusions remain unchanged.
26 July 2021	New search has been performed	We updated the search strategy to exclude studies evaluating positioning amongst neonates. This topic is now covered by the Cochrane Neonatal Group. However, the evidence for the management of infants or children as a separate group is unavailable. Four new authors joined the team. We included one new trial (Baudin 2019), and excluded 36 new trials. We updated the rationale for this review, we added the GRADE assessment for an additional (fourth) outcome comparison, and we updated our risk of bias assessment using the Cochrane RoB 2 for assessing parallel and cross‐over controlled trials.

History

Protocol first published: Issue 2, 2002
Review first published: Issue 2, 2005

Date	Event	Description
12 April 2012	New search has been performed	Searches conducted. One new study was identified (Oliveira 2009), but our conclusions remain unchanged. Additional details were added to the Methods and the risk of bias tables.
26 August 2011	New citation required but conclusions have not changed	A new author joined the team to update this review.
7 August 2008	New search has been performed	Searches conducted. We included two new studies in this updated review.
14 February 2008	Amended	Converted to new review format.
13 July 2006	Amended	Plain language summary re‐written.
24 October 2004	New search has been performed	Searches conducted.

Appendices

Appendix 1. MEDLINE Ovid search strategy (2021 search)

1. exp Bronchiolitis/
2. Bronchiolitis.tw.
3. exp respiratory syncytial virus infections/
4. Respiratory syncytial virus.tw.
5. RSV.tw.
6. Bronchopneumonia.tw.
7. exp bronchial diseases/
8. exp respiratory distress syndrome, adult/
9. ARDS.tw.
10. Acute respiratory distress.tw.
11. Acute lung injury.tw.
12. ALI.tw.
13. exp respiratory tract infections/
14. Respiratory distress.tw.
15. (Resp$ adj25 distress).tw.
16. (Bronch$ adj25 distress).tw.
17. Respiratory infection.tw.
18. exp respiratory insufficiency/
19. Respiratory insufficiency.tw.
20. Respiratory failure.tw.
21. Respiratory distress syndrome.tw.
22. exp pneumonia/
23. Pneumonia.tw.
24. exp lung diseases/
25. exp hyaline membrane disease/
26. Hyaline membrane disease.tw.
27. exp Bronchopulmonary dysplasia/
28. Bronchopulmonary dysplasia.tw.
29. 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18 or 19 or 20 or 21 or 22 or 23 or 24 or 25 or 26 or 27 or 28
30. exp posture/
31. Postur$.tw.
32. Supine.tw.
33. Prone.tw.
34. (Face adj5 down).tw.
35. (Side adj5 lying).tw.
36. Lateral$.tw.
37. (Kinetic adj5 position$).tw.
38. Continuous body position$.tw.
39. Upright.tw.
40. (High adj5 sitting).tw.
41. Semirecumbent.tw.
42. Position$.tw.
43. 30 or 31 or 32 or 33 or 34 or 35 or 36 or 37 or 38 or 39 or 40 or 41 or 42
44. randomized controlled trial.pt.
45. controlled clinical trial.pt.
46. randomized.ab.
47. placebo.ab.
48. drug therapy.fs.
49. randomly.ab.
50. trial.ab.
51. groups.ab.
52. 44 or 45 or 46 or 47 or 48 or 49 or 50 or 51
53. exp animals/ not humans.sh.
54. 9 not 10
55. 29 and 31 and 54
 

Appendix 2. Embase Ovid search strategy (2021 search)

1. 'bronchiolitis'/
2. bronchiolit*.ab,ti.
3. 'respiratory syncytial virus infection'/ or 'respiratory syncytial pneumovirus'/
4. ('respiratory syncytial virus' or 'respiratory syncytial viruses' or rsv).ab,ti.
5. 'bronchus disease'/
6. 'bronchopneumonia'/
7. bronchopneumon*.ab,ti.
8. 'acute lung injury'/
9. ('acute lung injury' or 'acute lung injuries' or ali).ab,ti.
10. 'respiratory tract infection'/
11. (respir* adj5 infect*).ab,ti.
12. (respir* adj3 (insufficien* or fail*)).ab,ti.
13. 'lung disease'/
14. pneumon*.ab,ti.
15. (distress* adj2 (respir* or bronch*)).ab,ti.
16. (ards or rds).ab,ti.
17. 'hyaline membrane disease'/
18. 'hyaline membrane disease'.ab,ti.
19. ('chronic neonatal lung disease' or 'chronic neonatal lung diseases').ab,ti.
20. 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18 or 19
21. 'body posture'/
22. (postur* or supine or prone or (face adj5 down*) or (side adj5 (lay or laying or laid or lying or lies or lays)) or lateral* or (kinetic adj5 position*) or 'continuous body position' or 'continuous body positions' or upright or (high adj5 sitting) or 'semi‐recumbent' or semirecumbent or 'semirecline' or semirecline or position*).ab,ti.
23. 21 or 22
24. 20 and 23
25. 'randomized controlled trial'/exp or 'single blind procedure'/exp or 'double blind procedure'/exp or 'crossover procedure'/
26. (random* or placebo* or factorial* or crossover* or 'cross‐over' or 'cross over' or assign* or allocat* or volunteer* or ((singl* or doubl*) adj2 (blind* or mask*))).ab,ti.
27. 25 or 26
28. 24 and 27

Appendix 3. CINAHL EBSCO search strategy (2021 search)

S48 S37 and S47
S47 S39 or S40 or S41 or S42 or S43 or S44 or S45 or S46 or S47
S46 (MH "Quantitative Studies")
S45 (MH "Random Assignment")
S44 (MH "Placebos")
S43TI placebo* or AB placebo*
S42 TI random* or AB random*
S41 TI (singl* blind* or doubl* blind* or trebl* blind* or tripl* blind* or singl* mask* or doubl* mask* or trebl* mask* or tripl* mask*)
or AB (singl* blind* or doubl* blind* or trebl* blind* or tripl* blind* or singl* mask* or doubl* mask* or trebl* mask* or tripl* mask*)
S40 TI clinic* trial* or AB clinic* trial*
S39 PT clinical trial
S38 (MH "Clinical Trials+")
S37 S22 and S36
S36 S23 or S24 or S25 or S26 or S27 or S28 or S29 or S30 or S31 or S32 or S33 or S34 or S35
S35 TI position* or AB position*
S34 TI (semi‐recumbent or semirecumbent or semi‐reclin* or semireclin*) or AB (semi‐recumbent or semirecumbent or semi‐reclin* or semireclin*)
S33 TI high N5 sitting or AB high N5 sitting
S32 TI upright or AB upright
S31 TI continuous body position* or AB continuous body position*
S30 TI kinetic N5 position* or AB kinetic N5 position*
S29 TI lateral* or AB lateral*
S28 TI side N5 laid or AB side N5 laid
S27 TI side N5 lying or AB side N5 lying
S26 TI side N5 lies or AB side N5 lies
S25 TI side N5 lay* or AB side N5 lay*
S24 TI face N5 down* or AB face N5 down*
S23 TI (supine or prone or postur*) or AB (supine or prone or postur*)
S22 (MH "Posture+")
S21 S1 or S2 or S3 or S4 or S5 or S7 or S8 or S9 or S10 or S11 or S12 or S13 or S14 or S15 or S16 or S17 or S18 or S19 or S20
S20 TI hyaline membrane disease* or AB hyaline membrane disease*
S19 TI (ards or rds) or AB (ards or rds)
S18 TI bronch* N25 distress* or AB bronch* N25 distress*
S17 TI respir* N25 distress* or AB respir* N25 distress*
S16 TI pneumon* or AB pneumon*
S15 TI respir* N3 fail* or AB respir* N3 fail*
S14 (MH "Bronchial Diseases+")
S13 TI respir* N3 insufficien* or AB respir* N3 insufficien*
S12 (MH "Lung Diseases+")
S11 "respiratory insufficiency"
S10 TI respir* N5 infect* or AB respir* N5 infect*
S9 (MH "Respiratory Tract Infections+")
S8 TI (acute lung injury or ali) or AB (acute lung injury or ali)
S7 TI bronchopneumon* or AB bronchopneumon*
S6 (MH "Bronchial Diseases")
S5 TI ( respiratory syncytial virus* or rsv ) or AB (respiratory syncytial virus* or rsv)
S4 (MH "Respiratory Syncytial Virus Infections")
S3 (MH "Respiratory Syncytial Viruses")
S2 TI bronchiolit* or AB bronchiolit*
S1 (MH "Bronchiolitis+")

Appendix 4. Search strategies used in previous versions

1 MEDLINE Ovid search strategy

1 exp Lung Diseases/ (692599)
2 exp Bronchial Diseases/ (160999)
3 exp Respiratory Tract Infections/ (288514)
4 exp Respiratory Insufficiency/ (51190)
5 ((respir* or bronch*) adj3 (insuffic* or fail* or distress*)).tw. (51957)
6 (acute lung injur* or ali).tw. (9361)
7 (ards or rds).tw. (10766)
8 (respiratory adj5 infect*).tw. (38064)
9 (pneumon* or bronchopneumon*).tw. (128563)
10 (bronchit* or bronchiolit*).tw. (25002)
11 ((neonatal lung or neonatal respiratory) adj1 (diseas* or injur* or infect* or illness*)).tw. (316)
12 hyaline membrane diseas*.tw. (1609)
13 bronchopulmonary dysplasia.tw. (4003)
14 (croup or laryngotracheobronchit* or epiglottit* or whooping cough or legionel*).tw. (11864)
15 (laryng* adj2 infect*).tw. (618)
16 (acute adj2 (episode or exacerbation*) adj3 (asthma or bronchiectasis or cystic fibrosis)).tw. (975)
17 respiratory syncytial viruses/ or respiratory syncytial virus, human/ (6404)
18 Respiratory Syncytial Virus Infections/ (4740)
19 (respiratory syncytial virus* or rsv).tw. (11550)
20 or/1‐19 (959468)
21 exp Posture/ (61565)
22 (postur* or position*).tw. (421035)
23 (supine or prone or semi‐prone).tw. (62142)
24 ((face or facing) adj5 down*).tw. (599)
25 (side adj5 (lay or laying or laid or lays or lying or lies)).tw. (695)
26 lateral.tw. (194949)
27 upright.tw. (10446)
28 (semi‐recumbent or semirecumbent or semi‐reclin* or semireclin* or reclin* or recumbent).tw. (2970)
29 ((high or erect or non‐erect or lean* or forward) adj5 (sit or sitting)).tw. (400)
30 (body adj3 tilt*).tw. (546)
31 (elevat* adj3 head*).tw. (787)
32 or/21‐31 (669104)
33 20 and 32 (16342)

2 Embase.com search strategy

#28 #24 AND #27 116416 Jan 2011
#27 #25 OR #26 83206316 Jan 2011
#26 random*:ab,ti OR placebo*:ab,ti OR factorial*:ab,ti OR crossover*:ab,ti OR 'cross‐over':ab,ti OR 'cross over':ab,ti OR assign*:ab,ti OR allocat*:ab,ti OR volunteer*:ab,ti OR ((singl* OR doubl*) NEAR/2 (blind* OR mask*)):ab,ti AND [embase]/lim79319116 Jan 2011
#25 'randomized controlled trial'/exp OR 'single blind procedure'/exp OR 'double blind procedure'/exp OR 'crossover procedure'/exp AND [embase]/lim 23497116 Jan 2011
#24 #20 AND #23 1301916 Jan 2011
#23 #21 OR #22 52233216 Jan 2011
#22 postur*:ab,ti OR supine:ab,ti OR prone:ab,ti OR (face NEAR/5 down*):ab,ti OR (side NEAR/5 (lay OR laying OR laid OR lying OR lies OR lays)):ab,ti OR lateral*:ab,ti OR (kinetic NEAR/5 position*):ab,ti OR 'continuous body position':ab,ti OR 'continuous body positions':ab,ti OR upright:ab,ti OR (high NEAR/5 sitting):ab,ti OR 'semi‐recumbent':ab,ti OR semirecumbent:ab,ti OR 'semi‐recline':ab,ti OR semirecline:ab,ti OR position*:ab,ti AND [embase]/lim51802216 Jan 2011
#21 'body posture'/de AND [embase]/lim21003 16 Jan 2011
#20 #1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11 OR #12 OR #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19 679544 16 Jan 2011
#19 'chronic neonatal lung disease':ab,ti OR 'chronic neonatal lung diseases':ab,ti AND [embase]/lim29 16 Jan 2011
#18 'hyaline membrane disease':ab,ti AND [embase]/lim1319 16 Jan 2011
#17 'hyaline membrane disease'/de AND [embase]/lim2972 16 Jan 2011
#16 ards:ab,ti OR rds:ab,ti AND [embase]/lim9686 16 Jan 2011
#15 (distress* NEAR/2 (respir* OR bronch*)):ab,ti AND [embase]/lim22691 16 Jan 2011
#14 pneumon*:ab,ti AND [embase]/lim99195 16 Jan 2011
#13 'lung disease'/exp AND [embase]/lim513379 16 Jan 2011
#12 (respir* NEAR/3 (insufficien* OR fail*)):ab,ti AND [embase]/lim22834 16 Jan 2011
#11 (respir* NEAR/5 infect*):ab,ti AND [embase]/lim32004 16 Jan 2011
#10 'respiratory tract infection'/exp AND [embase]/lim147424 16 Jan 2011
#9 'acute lung injury':ab,ti OR 'acute lung injuries':ab,ti OR ali:ab,ti AND [embase]/lim 7550 16 Jan 2011
#8 'acute lung injury'/de AND [embase]/lim 3542 16 Jan 2011
#7 bronchopneumon*:ab,ti AND [embase]/lim 2178 16 Jan 2011
#6 'bronchopneumonia'/de AND [embase]/lim 3002 16 Jan 2011
#5 'bronchus disease'/exp AND [embase]/lim 6865616 Jan 2011
#4 'respiratory syncytial virus':ab,ti OR 'respiratory syncytial viruses':ab,ti OR rsv:ab,ti AND [embase]/lim 904616 Jan 2011
#3 'respiratory syncytial virus infection'/de OR 'respiratory syncytial pneumovirus'/de AND [embase]/lim 877916 Jan 2011
#2 bronchiolit*:ab,ti AND [embase]/lim 644716 Jan 2011
#1 'bronchiolitis'/exp AND [embase]/lim 876316 Jan 2011

3 CINAHL search strategy

S45 S44 AND EM 201202‐ CINAHL 61
S44 S33 AND S43 CINAHL 378
S43 S34 OR S35 OR S36 OR S37 OR S38 OR S39 OR S40 OR S41 OR S42 CINAHL 207,055
S42 (MH "Quantitative Studies") CINAHL 9,853
S41 TI placebo* OR AB placebo* CINAHL 21,717
S40 (MH "Placebos") CINAHL 7,026
S39 (MH "Random Assignment") CINAHL 30,993
S38 TI random* OR AB random* CINAHL 110,457
S37 TI ((singl* or doubl* or tripl* or trebl*) W1 (blind* or mask*)) OR AB ((singl* or doubl* or tripl* or trebl*) W1 (blind* or mask*)) CINAHL 15,872
S36 TI clinic* trial* OR AB clinic* trial* CINAHL 34,075
S35 PT clinical trial CINAHL 51,429
S34 (MH "Clinical Trials+") CINAHL 122,002
S33 S20 AND S32 CINAHL 2,526
S32 S21 OR S22 OR S23 OR S24 OR S25 OR S26 OR S27 OR S28 OR S29 OR S30 OR S31 CINAHL 59,985
S31 TI elevat* N3 head* OR AB elevat* N3 head* CINAHL 227
S30 TI body N3 tilt* OR AB body N3 tilt* CINAHL 40
S29 TI ((high or erect or non‐erect or lean* or forward) N5 (sit or sitting)) OR AB ((high or erect or non‐erect or lean* or forward) N5 (sit or sitting)) CINAHL 146
S28 TI (semi‐recumbent or semirecumbent or semi‐reclin* or semireclin* or reclin* or recumbent) OR AB (semi‐recumbent or semirecumbent or semi‐reclin* or semireclin* or reclin* or recumbent) CINAHL 420
S27 TI upright OR AB upright CINAHL 1,229
S26 TI lateral OR AB lateral CINAHL 13,235
S25 TI (side N5 (lay or laying or laid or lays or lying or lies)) OR AB (side N5 (lay or laying or laid or lays or lying or lies)) CINAHL 175
S24 TI ((face or facing) N5 down*) OR AB ((face or facing) N5 down*) CINAHL 113
S23 TI (supine or prone or semi‐prone) OR AB (supine or prone or semi‐prone) CINAHL 5,954
S22 TI (postur* or position*) OR AB (postur* or position*) CINAHL 41,900
S21 (MH "Body Positions") OR (MH "Lateral Position") OR (MH "Posture") OR (MH "Prone Position") OR (MH "Supine Position") CINAHL 7,567
S20 S1 OR S2 OR S3 OR S4 OR S5 OR S6 OR S7 OR S8 OR S9 OR S10 OR S11 OR
S12 OR S13 OR S14 OR S15 OR S16 OR S17 OR S18 OR S19 CINAHL 129,550
S19 TI (respiratory syncytial virus* or rsv) OR AB (respiratory syncytial virus* or rsv) CINAHL 914
S18 (MH "Respiratory Syncytial Viruses") CINAHL 328
S17 (MH "Respiratory Syncytial Virus Infections") CINAHL 847
S16 TI (("acute episode" or "acute exacerbation" or "acute exacerbations") N3 (asthma or bronchiectasis or cystic fibrosis)) OR AB (("acute episode" or "acute exacerbation" or "acute exacerbations") N3 (asthma or bronchiectasis or cystic fibrosis)) CINAHL 109
S15 TI laryng* N2 infect* OR AB laryng* N2 infect* CINAHL 23
S14 TI (croup or laryngotracheobronchit* or epiglottit* or whooping cough or legionel*) OR AB (croup or laryngotracheobronchit* or epiglottit* or whooping cough or legionel*) CINAHL 1,025
S13 TI bronchopulmonary dysplasia OR AB bronchopulmonary dysplasia CINAHL 758
S12 TI hyaline membrane diseas* OR AB hyaline membrane diseas* CINAHL 45
S11 TI (("neonatal lung" or "neonatal respiratory") N1 (diseas* or injur* or infect* or illness*)) OR AB (("neonatal lung" or "neonatal respiratory") N1 (diseas* or injur* or infect* or illness*)) CINAHL 55
S10 TI (bronchit* or bronchiolit*) OR AB (bronchit* or bronchiolit*) CINAHL 1,861
S9 TI (pneumon* or bronchopneumon*) OR AB (pneumon* or bronchopneumon*) CINAHL 11,258
S8 TI respiratory N5 infect* OR AB respiratory N5 infect* CINAHL 4,062
S7 TI (ards or rds) OR AB (ards or rds) CINAHL 1,445
S6 TI (acute lung injur* or ali) OR AB (acute lung injur* or ali) CINAHL 1,640
S5 TI ((respir* or bronch*) N3 (insuffic* or fail* or distress*)) OR AB ((respir* or bronch*) N3 (insuffic* or fail* or distress*)) CINAHL 5,997
S4 (MH "Respiratory Failure+") CINAHL 6,325
S3 (MH "Respiratory Tract Diseases+") CINAHL 121,891
S2 (MH "Bronchial Diseases+") CINAHL 21,227
S1 (MH "Lung Diseases+") CINAHL 71,495

4. 2012 search strategy

In 2012, we searched CENTRAL, 2012, Issue 3, in the Cochrane Library, (accessed 12 April 2012), which contains the Acute Respiratory Infections Group's Specialised Register, MEDLINE (June 2008 to April week 1, 2012), Embase (January 2010 to April 2012) and CINAHL (2008 to April 2012).

We searched MEDLINE and CENTRAL using the following search strategy. We combined the MEDLINE search terms with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE, sensitivity‐ and precision‐maximising version (2008 revision); Ovid format (Lefebvre 2021). The search strategy was adapted to search Embase and CINAHL.

MEDLINE Ovid

1 exp Bronchiolitis/
2 bronchiolit*.tw.
3 Respiratory Syncytial Virus Infections/
4 respiratory syncytial viruses/ or respiratory syncytial virus, human/
5 (respiratory syncytial virus* or rsv).tw.
6 exp Bronchial Diseases/
7 bronchopneumon*.tw.
8 (acute lung injur* or ali).tw.
9 exp Respiratory Tract Infections/
10 (respir* adj5 infect*).tw.
11 exp Respiratory Insufficiency/
12 (respir* adj3 (insufficien* or fail*)).tw.
13 exp Lung Diseases/
14 pneumon*.tw.
15 ((respir* or bronch*) adj25 distress*).tw.
16 (ards or rds).tw.
17 hyaline membrane disease*.tw.
18 bronchopulmonary dysplasia.tw.
19 chronic neonatal lung disease*.tw.
20 or/1‐18
21 exp Posture/
22 postur*.tw.
23 supine.tw.
24 prone.tw.
25 (face adj5 down*).tw.
26 (side adj5 (lay or laying or laid or lays or lying or lies)).tw.
27 lateral*.tw.
28 (kinetic adj5 position*).tw.
29 continuous body position*.tw.
30 upright.tw.
31 (high adj5 sitting).tw.
32 (semi‐recumbent or semirecumbent or semi‐recline* or semirecline*).tw.
33 position*.tw.
34 or/21‐33
35 20 and 34

For the 2008 update, we searched CENTRAL, 2008, Issue 3, in the Cochrane Library, which contains the Acute Respiratory Infections Group's Specialised Register; MEDLINE (January 1966 to August Week 1, 2008); Embase (January 2004 to Week 33, 2008), and CINAHL (January 2004 to August Week 3, 2008).

We combined the MEDLINE search terms with a search strategy used to identify relevant trials (Dickersin 1994). We adapted the search terms to search Embase and CINAHL.

TERMS FOR ACUTE RESPIRATORY DISTRESS

1 Exp Bronchiolitis/
2 Bronchiolitis.tw
3 Exp respiratory syncytial virus infections/
4 Respiratory syncytial virus.tw
5 RSV.tw
6 Bronchopneumonia.tw
7 Exp bronchial diseases/ [incorporates asthma, bronchopneumonia]
8 Exp respiratory distress syndrome, adult/
9 ARDS.tw
10 (Acute respiratory distress).tw
11 Acute lung injury.tw
12 ALI.tw
13 Exp respiratory tract infections/
14 Respiratory distress.tw
15 (Resp$ adj25 distress).tw
16 (Bronch$ adj25 distress).tw
17 Respiratory infection.tw
18 Exp respiratory insufficiency/ [Used for respiratory failure]
19 Respiratory insufficiency.tw
20 Respiratory failure.tw
21 Exp respiratory distress syndrome/
22 Respiratory distress syndrome.tw
23 Exp pneumonia/
24 Pneumonia.tw
25 Exp lung diseases/ [incorporates pneumonia, RDS]
26 Exp hyaline membrane disease/
27 Hyaline membrane disease.tw
28 Exp Bronchopulmonary dysplasia/
29 Bronchopulmonary dysplasia.tw
30 Chronic neonatal lung disease.tw
31 Or/1‐30

POSITIONING TERMS
32 Exp posture/ [This will capture (exp supine position/) and (exp prone position/)]
33 Postur$.tw
34 Supine.tw
35 Prone.tw
36 Face adj5 down.tw
37 Side adj5 lying.tw
38 Lateral$.tw
39 Kinetic adj5 position$.tw
40 Continuous body position$.tw
41 Upright.tw
42 High adj5 sitting.tw
43 Semirecumbent.tw
44 Position$.tw
45 Or/32‐44
46 31 and 45

Data and analyses

Comparison 1. Prone versus supine positioning.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 SaO2	1	60	Mean Difference (IV, Fixed, 95% CI)	0.40 [‐1.22, 2.02]
1.1.1 Upper respiratory Indices	1	26	Mean Difference (IV, Fixed, 95% CI)	‐0.50 [‐2.58, 1.58]
1.1.2 Lower respiratory Indices	1	34	Mean Difference (IV, Fixed, 95% CI)	1.80 [‐0.78, 4.38]
1.2 PaCO2	1	99	Mean Difference (IV, Fixed, 95% CI)	3.00 [‐1.93, 7.93]
1.3 PaO2	1	99	Mean Difference (IV, Fixed, 95% CI)	2.00 [‐5.29, 9.29]
1.4 PaO2/FiO2 ratio	2	121	Mean Difference (IV, Random, 95% CI)	28.16 [‐9.92, 66.24]
1.5 Oxygenation index (parallel trials)	2	121	Mean Difference (IV, Fixed, 95% CI)	‐2.42 [‐3.60, ‐1.25]
1.6 Oxygenation index (cross‐over trial)	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
1.6.1 30 minutes	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
1.6.2 2 hour	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
1.6.3 4 hours	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
1.6.4 6 hours	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
1.6.5 8 hours	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
1.6.6 12 hours	1		Mean Difference (IV, Fixed, 95% CI)	Totals not selected
1.7 Tidal volume	1	84	Mean Difference (IV, Fixed, 95% CI)	‐0.60 [‐1.05, ‐0.15]
1.8 Respiratory compliance	1	20	Mean Difference (IV, Fixed, 95% CI)	0.07 [‐0.10, 0.24]
1.9 Positive end‐expiratory pressure (PEEP)	1	20	Mean Difference (IV, Fixed, 95% CI)	‐0.70 [‐2.72, 1.32]
1.10 Respiratory resistance	1	20	Mean Difference (IV, Fixed, 95% CI)	‐0.00 [‐0.05, 0.04]
1.11 Potential adverse outcomes	1	408	Odds Ratio (M‐H, Fixed, 95% CI)	1.07 [0.53, 2.14]
1.11.1 Extubation	1	102	Odds Ratio (M‐H, Fixed, 95% CI)	0.58 [0.13, 2.54]
1.11.2 Obstructed endotracheal tube	1	102	Odds Ratio (M‐H, Fixed, 95% CI)	5.20 [0.24, 111.09]
1.11.3 Pressure ulcers	1	102	Odds Ratio (M‐H, Fixed, 95% CI)	1.00 [0.41, 2.44]
1.11.4 Hypercapnia	1	102	Odds Ratio (M‐H, Fixed, 95% CI)	3.06 [0.12, 76.88]

Comparison 2. Supine versus good‐lung dependent positioning.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 PaO2 (cross‐over trial)	1	50	Mean Difference (IV, Fixed, 95% CI)	3.44 [‐23.12, 30.00]

Comparison 3. Supine versus good‐lung independent positioning.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
3.1 PaO 2 (cross‐over trial)	1	50	Mean Difference (IV, Fixed, 95% CI)	‐2.78 [‐28.84, 23.28]

Comparison 4. Good‐lung independent versus good‐lung dependent positioning.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4.1 PaO2 (cross‐over trial)	1	50	Mean Difference (IV, Fixed, 95% CI)	6.22 [‐21.25, 33.69]

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Baudin 2019.

Study characteristics
Methods	Cross‐over RCT of prone and supine positions
Participants	Severe bronchiolitis requiring non‐invasive ventilation
Interventions	14 infants with a diagnosis of viral bronchiolitis were randomised to receive 7 cm H2O continuous positive airway pressure for 1 hour in the prone position or in the supine position, which was followed by cross‐over to the supine position or the prone position for 1 hour, opposite to which they had been in phase one.
Outcomes	Modified Wood clinical asthma score, transcutaneous partial pressure of carbon dioxide, inspired fraction of oxygen, pulse oximetry, and heart rate
Notes	Funded by a grant from the Fonds de recherche en santé du Québec.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The randomisation sequence was generated by the clinical investigation centre of the Hospices Civils de Lyon, France. Infants were randomised using an online data management software (Clinsigh, Ennov, Paris, France) to receive either the supine position then the prone position, or the converse.
Allocation concealment (selection bias)	Low risk	The randomisation sequence was central, generated by the clinical investigation within the centre. An online software was used which could have concealed the order of randomisation but may be easy to uncover considering the small study population.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated. Participants were infants, and blinding would have been difficult to achieve, since nurses and caregivers would have been aware of the child's intervention group before crossing over, but outcomes were objective and less prone to bias.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Participants were enrolled between November 2015 and January 2016. 16 participants were included in the study and 2 participants were excluded from the analysis owing to a technical problem with the data acquisition system. The number of patient data lost was minimal.

Curley 2005.

Study characteristics
Methods	Parallel RCT of prone and supine positions
Participants	Included: 102 intubated and ventilated paediatric participants (2 weeks to 18 years) with a PaO2/FiO2 of less than or equal to 300, bilateral pulmonary infiltrates and no clinical evidence of left atrial hypertension Excluded: less than 42 weeks post‐conceptual age, unable to tolerate a position change, respiratory failure due to cardiac disease, hypoxaemia without bilateral infiltrates, bone marrow or lung transplant, receiving extracorporeal membrane oxygenation, a non‐pulmonary condition that was exacerbated by the prone position, participated in another trial within previous 30 days, the decision to limit life support Median age: 2 years; median FiO2: 0.60; diagnosis: pneumonia (28), bronchiolitis with pneumonia (8), sepsis (7), aspiration (6), other (2) Setting: 7 paediatric ICUs, USA
Interventions	Participants were placed in the prone position 20 hours/day while in the acute phase of their illness up to a maximum of 7 days; the median time in each position (acute phase) was 4 days in the prone group and 5 days in the supine group
Outcomes	OI; PaO2; PaCO2; tidal volume; minute ventilation; FiO2; PaO2/FiO2; PEEP; extubations; obstructed ETT; pressure ulcers; hypercapnia
Notes	Mortality was also reported at 28 days, however, as the intervention continued only up to a maximum of 7 days, we did not include these data in this review The study was funded by the NIH/NINR.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation performed using a permuted block design
Allocation concealment (selection bias)	Low risk	Serial numbered opaque sealed envelopes were used
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Data collection was not blinded but outcomes were not subjective
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Loss to follow‐up 1/102 because consent was withdrawn

Ibrahim 2007.

Study characteristics
Methods	Parallel RCT of prone and supine positions
Participants	Included: 34 children aged 8 weeks to 10 years on mechanical ventilation for acute respiratory failure Excluded: participants with cardiac or neurological disease, chest or abdominal trauma, neurological surgery, unstable circulatory system or receiving extracorporeal membrane oxygenation Median age: 12 months; FiO2: 0.5; diagnosis: sepsis (13), pneumonia (12), inhalation injury (5), drowning (2) Setting: paediatric ICU, Saudi Arabia
Interventions	Prone and supine for 20 hours, both groups also received inhaled nitric oxide
Outcomes	OI; PaO2/FiO2 at 1 hour and 20 hours
Notes	Outcome data were also collected at 24 hours, however, as children in the prone group were changed to the supine position at 20 hours, these data were not included. Study supported by Al‐Noor specialist hospital‐KSA.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Outcome assessment was not blinded but outcomes were not subjective
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Loss to follow‐up 2/34; 1 because PaO2 improved and the other because of clinical deterioration

Kornecki 2001.

Study characteristics
Methods	Cross‐over RCT of prone and supine positions
Participants	Included: 10 children aged 8 weeks to 16 years who required mechanical ventilation for moderate to severe acute respiratory failure Excluded: not stated Mean age: 5 years; mean weight: 22.5 kg; diagnosis: sepsis/acute respiratory distress syndrome (4), pneumonia (3), other (3) Setting: 36‐bed paediatric critical care unit in a tertiary care university‐based children's hospital in the USA
Interventions	Supine first, then random order of first study position; 12 hours in each position
Outcomes	Oxygenation index Data collected at 2, 4, 6, 8, 12 hours for each position
Notes	Heart rate, PaCO2 and arterial BP were not reported The study was supported by the Department of Critical Care Medicine, Division of Respiratory Medicine, Hospital for Sick Children, University of Toronto, Toronto, Ontario.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Loss to follow‐up: 2/12 patients were not enrolled because they could not be placed in prone position due to physical restrictions

Levene 1990.

Study characteristics
Methods	Cross‐over RCT of prone and supine positions
Participants	Included: 13 infants aged 2 to 11 months with upper respiratory tract infection and nasal discharge and 17 infants with lower respiratory tract infection, or bronchiolitis (as determined clinically by tachypnoea, fever, wheeze, crackles on auscultation) Excluded: infants with SaO2 < 85% in air Setting: UK
Interventions	After settling in each position for 10 minutes, infants remained in each position for 20 minutes All participants studied during quiet sleep
Outcomes	SaO2 continuously measured over 20 minutes
Notes	The study was funded by the North East Thames Regional Health Authority.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	High risk	Loss to follow‐up 9/39 infants as they did not go to sleep or woke when moved

Polacek 1992.

Study characteristics
Methods	Cross‐over RCT of supine, lateral atelectatic lung dependent; and lateral atelectatic lung non‐dependent positions
Participants	Included: 25 children, aged from 1 month to 10 years, and unilateral atelectasis who had undergone heart surgery within the previous 2 weeks, and had an indwelling arterial catheter Excluded: children with previous underlying disease, presence of pulmonary hypertension, presence of cardiac lesions with persistent intracardiac shunting Median age: 20 months; ventilation: mechanical ventilation (10), supplemental oxygen (9), spontaneously breathing room air (6) Setting: PICU in a tertiary paediatric hospital, USA
Interventions	All children were placed in the supine position first; only the order of the lateral positions were randomised Children were positioned for 15 minutes in each position over a total of 45 minutes
Outcomes	PaO2 Arterial blood gas sampled 15 minutes after position change
Notes	The study was supported by the Children's Mercy Hospital, Kansas City, Missouri.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	Appears to be no loss to follow‐up

BP: blood pressure
bpm: beats per minute
cm: centimetres
CPAP: continuous positive airways pressure
ETT: endotracheal tube
FiO₂: inspired oxygen
H2O: water
ICU: intensive care unit
kg: kilogram
kPa: kilopascal
m‐WCAS: modified Wood clinical asthma score
M_PAW: mean airway pressure
NICU: neonatal intensive care unit
NIH/NINR: National Institute for Health/National Institute for Nursing Research
O2: oxygen
OI: oxygenation index = (FiO₂% X M_PAW/ PaO₂)
PaCO₂: arterial carbon dioxide tension
PaO₂: arterial oxygen tension
PDA: patent ductus arteriosis
PEEP: positive expiratory end pressure
PICU: paediatric intensive care unit
RCT: randomised controlled trial
SaO₂: oxygen saturation of haemoglobin
tcO2: transcutaneous oxygen level
tcCO2: transcutaneous carbon dioxide level
UK: United Kingdom
USA: United States of America

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Akatsuka 2018	Wrong population
Anonymous 2005	Comment on Curley 2005
Ayzac 2016	Adult population
Baston 2019	Wrong study design
Bourenne 2018	Literature review
Brzęk 2019	Wrong study design
Casado‐Flores 2002	Wrong study design
Curley 2000	Wrong study design
Dalmedico 2017	Literature review
Du 2018	Wrong study design
Gattinoni 2018	Literature review
Guervilly 2019	Literature review
Hassankhani 2017	Adult population
Jang 2020	Wrong population
Johnson 2017	Literature review
Kamo 2018	Wrong study design
Kavanagh 2005	Comment on Curley 2005
Lee 2018	Wrong study design
Leger 2017	Wrong study design
Li 2018	Wrong intervention
Li Bassi 2017	Adult population
Li Bassi 2017a	Adult population
Li Bassi 2017b	Wrong population
Li Bassi 2017c	Wrong population
Munshi 2017	Wrong study design
Murdoch 1994	Not randomised
Najafi 2017	Wrong population
Panigada 2017a	Wrong population
Panigada 2017b	Wrong population
Pelosi 2001	Adult population
Pourazar 2018	Neonatal population
Teng 2018	Systematic review
Thompson 2013	Adult population
Trikha 2013	Adult population
Yonis 2017	Wrong outcomes
Yue 2017	Systematic review

Differences between protocol and review

New authors joined the team to update this review, and the previous lead author resigned from this update.

The search strategy was updated to exclude studies that evaluated positioning amongst neonates, defined as hospitalised infants aged more than 4 weeks, and children up to 16 years of age, with a primary or secondary diagnosis of acute respiratory distress, or with an acute exacerbation of a chronic respiratory illness. Previous reviews have evaluated neonates with children < 18 years old in combination. However, due to the differences in physiology and pathology that occur during the postpartum period, we decided to separate the two population groups.

We reported results on the sub‐analysis of upper and lower respiratory tract infections provided by Levene 1990.

An additional (fourth) outcome comparison was added to the review, as well as the GRADE assessment.

We also updated our quality assessment using recommended Cochrane risk of bias tool version 2, for assessing parallel and cross‐over controlled trials appropriately.

For the unit of analysis issues in the cross‐over trial by Baudin 2019, we used data from the first period only, to avoid possible carry‐over effects.

Contributions of authors

Abhishta P Bhandari: data extraction and drafting of the 2022 update
Daniel A Nnate: screening, analysis, drafting, and finalisation of the 2022 update
Lenny Vasanthan: screening, analysis, and drafting of the 2022 update
Menelaos Konstantinidis: analysis, drafting, and finalisation of the 2022 update
Jacqueline Y Thompson: screening, data extraction, analysis, drafting, and finalisation of the 2022 update.

Sources of support

Internal sources

• The Children's Hospital Westmead, Sydney, Australia

  Organisation

External sources

• University of Birmingham, UK

  Organisation

• Townsville University, Australia

  Organisation

Declarations of interest

Abhishta P Bhandari: declared that they have no conflict of interest
Daniel A Nnate: declared that they have no conflict of interest
Lenny Vasanthan: declared that they have no conflict of interest
Menelaos Konstantinidis: declared that they have no conflict of interest
Jacqueline Y Thompson: declared that they have no conflict of interest.

New search for studies and content updated (no change to conclusions)