Comparison of Spontaneous Ventilation, Pressure Control Ventilation and Pressure Support Ventilation in Pediatric Patients Undergoing Infraumbilical Surgery Using ProSeal Laryngeal Mask Airway

Abstract

Background:

Pediatric infraumbilical surgeries are often performed under general anaesthesia using different modes of ventilation through Laryngeal Mask Airway .Although controlled ventilation has been successfully used, very less studies have been done to compare them with spontaneous ventilation for short duration surgeries.

Aims:

We tried to measure quantitave differences in haemodynamic and respiratory parameters and assess the recovery profile between controlled and spontaneous ventilation using Proseal LMA.

Settings and Design:

This was a prospective, randomized, double-blind study that comprised 90 American Society of Anaesthesiologist (ASA) classes I and II pediatric patients posted for infra umbilical surgery.

Materials and Methods:

90 paediatric patients undergoing infraumbilical surgeries were included. Three different ventilation strategies: spontaneous , pressure support and pressure-controlled ventilation were applied depending on attending anaesthesiologist's preference. Haemodynamic and respiratory parameters were recorded during the procedure. Post procedure parameters including need for supplementary oxygen, recovery time, complications were recorded.

Statistical Methods:

Analysis of variance (ANOVA) was employed for inter group analysis and for multiple comparisons, least significant difference (LSD) test was applied. Chi-square test or Fisher's exact test, whichever appropriate, was used for comparison of categorical variables.

Results:

The mean time interval between end of surgery and removal of LMA was significantly higher in PCV group in comparison to SV and PSV groups. In SV group lesser number of patients required oxygen supplementation and had shorter stay in recovery than PCV group.

Conclusion:

We conclude that spontaneous mode of ventilation can be used as safely as controlled /assist ventilation mode in short duration surgeries in high turn over settings.

INTRODUCTION

Pediatric infraumbilical surgeries are often performed under general anesthesia using different modes of ventilation through laryngeal mask airway (LMA). For brief general anesthesia, supraglottic devices are being increasingly used with spontaneous ventilation (SV) in all age groups. Spontaneous breathing is a popular mode of ventilation with LMA, but it provides less effective gas exchange than does positive pressure ventilation especially when the depth of anesthesia is increased.[1,2,3] Pressure-controlled ventilation (PCV) has been used successfully through the LMA between 15 and 20 cm H₂O to prevent gastric insufflation or oropharyngeal leak.[4] The advantage of PCV over volume-controlled ventilation is that the peak inspiratory pressure (PIP) in the former is reduced at the same tidal volume (TV) and inspiratory time.[5,6] ProSeal LMA (PLMA) is a new version of LMA with a modified cuff and an esophageal drainage tube. When compared with the same-sized adult LMA, the pediatric PLMA provides a better oropharyngeal seal, as demonstrated by a higher airway leak pressure. This and a reduced tendency to produce gastric insufflation make positive pressure ventilation more effective with the PLMA than with the classic LMA.[7,8]

Pediatric patients may further benefit from pressure support in the operating room (OR) during anesthetic procedures. The advantage of the use of pressure support ventilation (PSV) is that it requires less pressure to obtain the same target TV than controlled mechanical ventilation. This reduced pressure requirement results in less air leakage during mechanical ventilation with supraglottic airway devices like LMA.[9,10] In addition, the resulting reduced intrathoracic pressure attenuates the effects of mechanical ventilation on hemodynamics and cardiac output especially in neonates.[11,12] However, we believe that controlled ventilation in short-duration pediatric infra umbilical surgeries in a high turnover settings leads to prolonged extubation time and longer stay in recovery. We hypothesized that SV in such settings can be used as safely as controlled ventilation.

The aim of our study was to determine the efficiency of spontaneous mode of ventilation in terms of hemodynamic and respiratory parameters and assess whether it translates to any difference in clinical outcome versus controlled ventilation using PLMA in pediatric patients.

MATERIALS AND METHODS

This prospective, randomized, double-blind study was conducted in the Department of Anesthesiology (Sher-I-Kashmir Institute of Medical Sciences Srinagar) during a 2-year period from January 2017 to January 2019.

After obtaining Institutional Ethical Committee approval (IEC-SKIMS RP 93/2017) and written informed consent from parents, 90 patients of either sex, aged between 1 and 5 years of the American Society of Anesthesiologists (ASA) Physical Status Classes I-II undergoing infraumbilical surgical procedures were included in the study.

Following patients were excluded from the study:

1. Anticipated difficult airway

2. Subjects with tracheostomies

3. Patients with hiatus hernia, gastro esophageal reflux disease

4. Upper respiratory tract infection

5. Full stomach.

Using G*Power software version 3.0.10 (Heinrich Heine University Dusseldorf, Germany), it was estimated that the least number of patients required in each group with effect size of 0.25, 80% power, and 5% significance level is 30. Since we had to compare three groups in our study, we included 90 patients in our study.

A thorough preoperative clinical assessment was done a day before surgery. The children selected for the study were kept fasting as per ASA fasting guidelines. Informed written consent was obtained from the parents or guardians. The children received premedication preoperatively with oral midazolam 0.5 mg.kg⁻¹ 1 h before surgery. On arrival to the OR, standard anesthetic monitors including electrocardiogram (ECG), noninvasive blood pressure, and pulse-oximeter were attached. Baseline vital parameters were recorded. Anesthesia was induced by inhalational induction with sevoflurane followed by intravenous line insertion. PLMA was inserted once there was no response to jaw thrust. Before inserting PLMA its posterior surface was well lubricated with 2% lignocaine jelly. The child's head was maintained in the sniffing position. The PLMA was then inserted using the index finger technique. The cuff was inflated with air as recommended by the manufacturer. After obtaining an effective airway (defined as normal thoracoabdominal movements, bilaterally equal audible breath sounds on auscultation, and a regular waveform on capnograph), the PLMA was fixed by taping over the maxilla.

Anesthesia was maintained with isoflurane 1% and oxygen between 30% and 40% and N₂O between 60% and 70%. Patients were then put on any one of the three modes of ventilation i.e., Group 1 or SV group, Group 2 or PCV group and Group 3 or PSV group depending upon attending anesthesiologist's preference. For PCV group, pressure limit and respiratory rate were governed by ETCO₂.Target ETCO₂ was 35 mmHg to 40 mmHg. A standard pediatric circle circuit connected to the anesthesia workstation was used. Data collection was done by anesthesiologist blinded to the group allocation.

For intraoperative analgesia and immediate postoperative analgesia, all patients received caudal epidural with 0.2% ropivacaine 1 mL.kg⁻¹ body weight. Supplemental analgesia was provided with fentanyl 1 μg.kg⁻¹ as needed. Respiratory parameters, which include respiratory rate, expired TV, end-tidal CO₂, SpO₂, inspired concentration of oxygen, peak airway pressure, and end-tidal isoflurane were monitored continuously and recorded every 5 min throughout surgery. An arterial blood gas sample was taken 30 min after induction of anesthesia. Hemodynamic parameters which include ECG and heart rate were monitored continuously, and noninvasive blood pressure was measured every 5 min for the whole duration of surgery.

The mean values of each of these parameters were computed for each patient, and these values were used for statistical analysis. At the end of surgery, PLMA was removed at end-tidal isoflurane of 0.8–0.9. Before transfer to recovery room, the time taken from the end of surgery to the removal of LMA was noted in all patients. Any adverse event such as laryngospasm, bronchospasm, aspiration, coughing, or breath-holding was recorded in the immediate postoperative period. In the recovery room, SpO₂ on arrival, the need for supplemental oxygen and its duration, nausea and/or vomiting as well as discharge time were recorded.

The primary outcome of our study was intraoperative respiratory parameters and recovery time. Whereas, hemodynamic parameters, blood gas parameters, supplemental oxygen requirement, and any adverse effects were secondary outcomes.

Statistical methods

The recorded data were compiled and entered into a SpreadSheet (Microsoft Excel) and then exported to the data editor of SPSS Version 20.0 (SPSS Inc., Chicago, Illinois, USA). Statistical software SPSS and Microsoft Excel were used to carry out the statistical analysis of data. Continuous variables were expressed as mean ± standard deviation and categorical variables were summarized as percentages. Analysis of variance was employed for inter-group analysis of data and for multiple comparisons, Least Significant Difference test was applied. Chi-square test or Fisher's exact test, whichever appropriate, was used for comparison of categorical variables. Graphically the data was presented by bar and line diagrams. A P < 0.05 was considered statistically significant. All P values were two-tailed.

RESULTS

A total of 90 patients in the age group of 1–5 years were included in the study. All the groups were comparable with respect to demographic characteristics such as age, sex, ASA status, and duration of surgery [Table 1].

Table 1.

Demographic characteristics of the study groups

Demographic parameter	Group 1 (n=30)	Group 2 (n=30)	Group 3 (n=30)	P
Age (years)	2.9±1.22	3.0±1.16	2.5±1.25	0.717
Sex (male/female)	26/4	27/3	25/5	0.735
Weight (kg)	12.9±2.47	13.1±2.84	12.3±2.68	0.212
ASA status (I/II)	22/8	24/6	25/5	0.682
Duration of surgery (min)	37.5±6.92	36.1±6.17	38.1±5.74	0.321

Data expressed as mean±SD and analyzed using unpaired t-test or n % and analyzed using Chi-square test. Group 1=Spontaneous ventilation, Group 2=Pressure control ventilation, Group 3=Pressure support ventilation, SD=Standard deviation, ASA=American Society of Anesthesiologists

The intraoperative hemodynamic parameters were comparable between the three groups [Table 2]. Respiratory rate (breaths min⁻¹) was significantly higher in SV group (29.65 ± 4.09) compared to PCV group (21.04 ± 2.25) and PSV group (21.83 ± 2.56) and was comparable between PCV group and PSV group. The mean TV (mL.kg⁻¹) generated in SV, PCV, PSV groups was 5.88 ± 0.64, 8.18 ± 1.03 and 8.10 ± 0.31 respectively. The difference was statistically significant between group SV versus PCV group (P < 0.001), SV group versus PSV group (P < 0.001) and comparable between group PCV versus PSV group (P = 0.592).

Table 2.

Hemodynamic parameters of the three groups

Parameter	Group 1 (n=30)	Group 2 (n=30)	Group 3 (n=30)	Intergroup comparison (P)
				1 versus 2	1 versus 3	2 versus 3
Heart rate (beats/min)	107.24±5.00	106.52±7.40	105.15±3.02	0.549	0.082	0.265
Mean arterial pressure (mmHg)	56.54±3.01	58.05±3.58	56.37±3.42	0.066	0.818	0.058
Oxygen saturation (%)	99.46±0.41	99.55±0.53	99.62±0.43	0.394	0.129	0.520

Data expressed as mean±SD and analyzed using unpaired t-test. Group 1=Spontaneous ventilation, Group 2=Pressure control ventilation, Group 3=Pressure support ventilation, SD=Standard deviation

Mean peak airway pressure (cm H₂O) in SV, PCV, PSV groups was 3.39 ± 0.40, 9.68 ± 1.46, and 11.23 ± 1.41, respectively. The peak pressures between three groups were statistically significant [Figure 1].

Figure 1.

Comparison of peak airway pressures in the three groups. Group 1: Spontaneous ventilation, Group 2: Pressure control ventilation, Group 3: Pressure support ventilation, AI: After induction, M: Minute

Arterial blood gas done at 30 min revealed that the pH in SV group was slightly acidotic compared to PCV and PSV group. PCO₂ was significantly higher in SV group compared to PCV and PSV [Figure 2].

Figure 2.

Line diagram depicting the changes in the mean end tidal CO₂ at various time intervals in the three groups. Group 1: Spontaneous ventilation, Group 2: Pressure control ventilation, Group 3: Pressure support ventilation, AI: After induction, M: Minute

The mean end-tidal CO₂ (mm Hg) in SV, PCV, PSV was 41.72 ± 1.77, 36.80 ± 0.87 and 36.92 ± 1.26, respectively. The difference was statistically significant between SV versus PCV (P < 0.001) and SV versus PSV (P < 0.001) [Figure 3].

Figure 3.

Bar diagram depicting the pH, PCO₂ and PO₂ in the ABG at 30 min in three groups. Group 1: Spontaneous ventilation, Group 2: Pressure control ventilation, Group 3: Pressure support ventilation

Mean time interval from end of surgery to removal of LMA was significantly higher in PCV compared to SV and PSV groups and comparable between SV and PSV group. In SV group lesser number of patients required oxygen supplementation in recovery room compared to PCV and PSV. The mean duration of supplemental oxygen requirement was higher in PCV compared to SV and PSV group. The duration of stay in recovery room was longer in PCV group compared to SV and PSV group [Table 3].

Table 3.

Postprocedure parameters between the three groups

Postprocedure parameter	Group 1 (n=30)	Group 2 (n=30)	Group 3 (n=30)	Intergroup comparison
				1 versus 2	1 versus 3	2 versus 3
End of surgery and LMA removal time (min)	1.8±0.69	3.6±1.20	2.0±0.73	<0.001*	0.336	<0.001*
SpO2 (%) on arrival to recovery room	96.5±1.29	96.1±1.08	96.4±1.13	0.060	0.160	0.634
Need for supplemental oxygen (yes/no)	26/16	34/4	32/8	0.001*	0.014*	0.319
Duration of stay in recovery room (min)	18.1±4.09	20.7±5.85	19.1±4.38	0.016*	0.345	0.141

*Statistically significant. Data expressed as mean±SD and analyzed using unpaired t-test or n % and analyzed using Chi-square test. Group 1=Spontaneous ventilation, Group 2=Pressure control ventilation, Group 3=Pressure support ventilation, LMA=Laryngeal mask airway, SD=Standard deviation

Postoperative complication like breath-holding and coughing were seen more in SV group compared to PCV and PSV groups. However, the difference was statistically insignificant between three groups.

DISCUSSION

Hypothetically, the spontaneous mode of ventilation is more physiological and more time-efficient in terms of time between end of surgery and removal of LMA and shorter recovery stay. However, increased work of breathing may be a concern, especially with prolonged procedures. This study was conducted to compare different modes of ventilation to see the physiological difference and evaluate the difference in terms of time efficiency and perioperative complications. In our study, respiratory rate and end-tidal CO₂ were significantly higher in SV group compared to PCV and PSV groups. Possible explanation might be because pediatric patients respond to increased inspiratory load of SV mode by increasing respiratory frequency as has also been evidenced by Tokioka et al.[9] A Study by Templeton et al.[13] who compared respiratory parameters using PLMA between three modes: SV, PSV, and PCV in children 12 months to 5 years of age. Found, respiratory rate was significantly higher in SV group compared to PSV group and PCV group. Respiratory rate was comparable between PSV group and PCV group.

Respiratory rate was comparable between PSV group and SV group in the study by Lim et al.[14] The possible explanation is their use of both inhalational and intravenous induction technique, unlike our study where only sevoflurane induction was used. Furthermore, they used sevoflurane for maintenance in their study whereas in our study we used isoflurane for maintenance. No significant difference in respiratory rate was seen between SV group, PSV group, and CMV group using LMA by Capdevila et al.[15] A possible reason may be that their study was conducted on adult patients whereas our study included pediatric patients who may respond to increased inspiratory load of SV mode by increasing respiratory rate.

TV in (mL.kg⁻¹) was significantly lower in SV group as compared to PCV and PSV groups. Lesser TV in SV group can be explained as patients were breathing spontaneously without any ventilatory assistance while PCV group and PSV were breathing with assistance from ventilator leading to the generation of adequate TV. Our results were comparable with study by Templeton et al.[13] who in their study found TV significantly lower in SV group compared to PSV group PCV group. TV was comparable between PSV group and PCV group. In the PCV mode of ventilation, the set desired PIP is adjusted to achieve adequate TV. Clinical studies have shown PCV may offer increased TV at a lower PIP and is recommended to limit the pressure in the airway and lungs like in patients with emphysema, and in neonates.[16]

Another study by Templeton et al.[17] also found that mean TV (mL.kg⁻¹) was significantly lower in SV group compared to PSV group and PCV group in children <1 year. TV was comparable between PSV group and PCV group (P = 2.61). Their results were comparable with our study. The results of our study were also comparable with a study by Lim et al.[14] They found that patients in Group PSV had higher expiratory TV per kg body weight compared with the patients in Group SV. Capdevila et al.[15] in their study found a significant difference in the TV generated intraoperatively between CMV group versus Spontaneous breathing group (P < 0.05), Spontaneous breathing group versus PSV group (P < 0.05). However, CMV group and PSV group had comparable TV.

In our study, end-tidal CO₂ (ETCO₂) was significantly higher in SV group compared to PCV and PSV group and comparable between PCV and PSV group.Templeton et al.[17] in their study found ETCO₂ was significantly higher in SV group versus PSV group and SV group versus PCV group. ETCO₂ was comparable between PSV group and PCV group. In their study, as no regional anesthesia was used, they used deeper levels of anesthesia unlike our study where caudal anesthesia was used in all patients so deeper levels were avoided. They used sevoflurane for maintenance whereas we used isoflurane for maintenance, which may have contributed to small difference in observed ETCO₂ between their study and our study. Lim et al.[14] in their study found that patients in PSV group had lower ETCO₂ compared with patients in group SV. They used sevoflurane for maintenance whereas we used isoflurane for maintenance, which may have contributed to small difference in observed in ETCO_2. Fiedler et al.[18] in their study observed lower values of ETCO₂ and respiratory rates because they used PEEP in their patients which provides better oxygenation and ventilation by reducing intrapulmonary shunts.

Mean pH was higher in SV group than PCV and PSV group. The mean PCO₂ (in mmHg) in SV group was higher than PCV and PSV groups. Three groups were comparable with respect to PO₂ (mmHg).

Soaida et al.[19] in their study divided infants (4–12 months) into two groups, Group 1 used PSV mode from start and Group 2 used spontaneous mode followed by switch to PSV mode once fatigue occurred. ABG was taken hourly in their study. The arterial pH value obtained in Group 1 versus Group 2 before rescue ventilatory change was statistically significant (P = 0.0228). The PCO₂ value obtained in Group 1 versus Group 2 before rescue ventilatory change was statistically significant (P = 0.002). The PO₂ value between the two groups before rescue ventilatory change was statistically insignificant (P = 0.50). These findings are in concordance with our study.

The saturation on arrival to recovery room was comparable between three groups. The results of our study are in concordance with study by Lim et al.[14] who in their study also found saturation on arrival to recovery room comparable between PSV and SV group (P = 0.22).

In SV group, 61.9% of patients needed oxygen supplementation in recovery room in comparison to 89.5% patients in PCV and 80% patients in PSV group. The difference was statistically significant between the three groups. The mean duration of oxygen supplementation in recovery room (min) was significantly longer in PCV group compared to SV group and PSV group and was comparable between SV group and PSV group. Duration of stay in recovery room was significantly higher in PCV group compared to SV group and comparable between SV group versus PSV and PCV group versus PSV group. The results of our study are in concordance with study by Lim et al.[14] who in their study found no significant difference in duration of stay in recovery room between PSV group and SV group. Postoperative complication like breath-holding and coughing was seen more in SV group compared to PCV and PSV group. However, the difference was statistically insignificant between three groups. Sinha et al.[20] in their study found that PCV with PEEP using PLMA was associated with lower adverse events than spontaneous respiration in infants and toddlers with upper respiratory infection. Although SV provides less effective gas exchange than does positive pressure ventilation especially when the depth of anesthesia is increased but in short infra umbilical procedures it does not translate into different clinical outcome as compared to controlled ventilation.

Despite promising and convincing results of recent clinical trials, lung-protective ventilation (LPV) has remained to be a “hot topic” among researchers in the field of anesthesia and critical care to decrease the incidence of postoperative pulmonary complications. The reason for this may be that mechanical ventilatory support applying intermittent positive pressure, regardless to the mode of ventilation (controlled, assisted, or intelligent dual-controlled mode), is nonphysiological, to say the least.

Individualization of ventilatory settings and maintaining physiological spontaneous breathing during mechanical ventilation may provide the opportunity for further improvement.

Limitations

The choice of ventilatory mode was based on individual anesthesiologist's preference which might vary between physicians depending upon expertise and individual patient characteristics.

Similar conclusions cannot be drawn about longer-duration surgeries.

CONCLUSION

We conclude that spontaneous mode of ventilation can be used as safely as PCV mode and PSV mode for pediatric patients undergoing short-duration surgical procedures using PLMA.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.