Abstract
Introduction
Sleep apnoea is the popular term for obstructive sleep apnoea-hypopnoea syndrome (OSAHS). OSAHS is abnormal breathing during sleep that causes recurrent arousals, sleep fragmentation, excessive daytime sleepiness, and nocturnal hypoxaemia. Apnoea may be "central", in which there is cessation of inspiratory effort, or "obstructive", in which inspiratory efforts continue but are ineffective because of upper airway obstruction. OSAHS affects up to 4% of men and 2% of women in the USA, with obesity being a major determinant.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of treatment for severe obstructive sleep apnoea-hypopnoea syndrome? What are the effects of treatment for non-severe obstructive sleep apnoea-hypopnoea syndrome? We searched: Medline, Embase, The Cochrane Library, and other important databases up to May 2008 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 43 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review we present information relating to the effectiveness and safety of the following interventions: nasal continuous positive airway pressure (CPAP); measures aimed at improving compliance with CPAP; oral appliances; and weight loss.
Key Points
Sleep apnoea is the popular term for obstructive sleep apnoea-hypopnoea syndrome (OSAHS). OSAHS is abnormal breathing during sleep that causes recurrent arousals, sleep fragmentation, daytime sleepiness, and nocturnal hypoxaemia.
Apnoea may be "central", in which there is cessation of inspiratory effort, or "obstructive", in which inspiratory efforts continue but are ineffective because of upper airway obstruction.
OSAHS affects up to 4% of men and 2% of women in the USA, with obesity being a major determinant.
In people with severe OSAHS, nasal CPAP has been shown to reduce daytime sleepiness compared with control treatments.
Although effective, it can be difficult getting people to comply with the prescribed CPAP regimen. Compliance seems no better with variations of CPAP, such as automatically titrated CPAP, bi-level positive airway pressure, patient-titrated CPAP, or CPAP plus humidification. We don't know whether educational or psychological interventions may improve compliance with CPAP.
Oral appliances that produce anterior advancement of the mandible seem to be effective in improving sleep-disordered breathing in people with OSAHS (either severe or non-severe).
Oral appliances are probably not as effective as CPAP, and we don't know how well they work in the long term.
We found no sufficient evidence judging the effectiveness of weight loss on OSAHS (either severe or non-severe), although there is consensus that advice about weight reduction is an important component of management of OSAHS.
Nasal CPAP also seems beneficial to people suffering from non-severe OSAHS.
Nasal CPAP is less acceptable in people with non-severe OSAHS, and we don't know whether measures aimed at improving compliance effectively increase usage.
Clinical context
About this condition
Definition
Sleep apnoea is the popular term for obstructive sleep apnoea-hypopnoea syndrome (OSAHS). OSAHS is abnormal breathing during sleep that causes recurrent arousals, sleep fragmentation, and nocturnal hypoxaemia. The syndrome includes daytime sleepiness, impaired vigilance and cognitive functioning, and reduced quality of life. Apnoea is the absence of airflow at the nose and mouth for at least 10 seconds, and hypopnoea is a major reduction (>50%) in airflow also for at least 10 seconds. Apnoeas may be "central", in which there is cessation of inspiratory effort, or "obstructive", in which inspiratory efforts continue but are ineffective because of upper airway obstruction. The diagnosis of OSAHS is made when a person with daytime symptoms has significant obstructive sleep-disordered breathing revealed by polysomnography (study of sleep state, breathing, and oxygenation) or by more limited studies (e.g., measurement of oxygen saturation overnight). Criteria for the diagnosis of significant sleep-disordered breathing have not been rigorously assessed, but have been set by consensus and convention. Diagnostic criteria have variable sensitivity and specificity. For example, an apnoea/hypopnoea index (AHI) of fewer than five episodes of apnoea or hypopnoea per hour of sleep is considered normal. However, people with upper airway resistance syndrome have an index below five episodes an hour, and many healthy older people have an index greater than five episodes an hour. In an effort to achieve international consensus, new criteria have been proposed and are becoming more widely used. The severity of OSAHS can be classified by the severity of two factors: daytime sleepiness (see table 1 ) and AHI (see table 2 ). Severe OSAHS is defined as severe sleep-disordered breathing (AHI >30 episodes per hour) plus symptoms of excessive daytime sleepiness (such as Epworth Sleepiness Scale >10 or Multiple Sleep Latency Test <5 minutes — see table 3 ). Central sleep apnoea and sleep-associated hypoventilation syndromes are not covered in this review.
Table 1.
Daytime sleepiness (see text).
| Severity of daytime sleepiness | Activities when unwanted sleepiness or involuntary sleep occurs | Functional effects |
| Mild | Activities that require little attention (e.g., watching TV, reading) | Minor impairment of social or occupational function |
| Moderate | Activities that require some attention (e.g., attending concerts, meetings, presentations) | Moderate impairment of social or occupational function |
| Severe | Activities that require more active attention (e.g., eating, conversation, walking, driving) | Marked impairment of social or occupational function |
Table 1.
Apnoea/hypopnoea index (see text).
| Severity of sleep-disordered breathing | AHI (episodes/hour of sleep) |
| Mild | 5–15 |
| Moderate | 15–30 |
| Severe | Over 30 |
AHI, apnoea/hypopnoea index.
Table 1.
Validated outcome measures (see text).
| Outcome measure (abbreviation) | Description | Scoring |
| Epworth Sleepiness Scale (ESS) | Questionnaire developed to measure the general level of sleepiness by the likelihood of falling asleep in 8 common situations | The score for each question ranges from 0 (no likelihood of falling asleep) to 3 (highly likely to fall asleep). A lower score indicates less daytime sleepiness in the last week Maximum score: 24 Normal: <11Severe: >16 |
| Multiple Sleep Latency test (MSLT) | A daytime sleep laboratory-based test in which the person is asked to try and fall asleep when placed in a quiet dark room for 20 minutes at 2-hourly intervals. Monitoring is by electroencephalography. The time between lights out and sleep onset (sleep latency) is measured in minutes. The mean value of 4–5 test sleeps in the day is calculated. The mean sleep latency is considered an "objective" sleep measure of daytime sleepiness. A reduced score indicates an increase in daytime sleepiness | Mean adult sleep latency of less than 5 minutes is indicative of pathological sleepiness Mild: 5–7 minutes Borderline: 8–9 minutes Normal: 10 minutes or more |
| Maintenance of Wakefulness Test (MWT) | Similar to the MSLT, but the person is asked to stay awake for 40 minutes in a dark room | Sleep latencies of less than 20 minutes are indicative of pathological sleepiness |
| Quality of life | ||
| Medical Outcomes Survey Short-Form 36 (SF-36) | A widely used short-form health survey that measures generic health-related quality of life across various populations. It is a 36-item questionnaire comprising 8 health concepts: physical functioning; role limitations attributable to physical health problems; bodily pain; social functioning; general mental health; role limitations attributable to emotional problems; vitality, energy or fatigue; and general health perceptions | Most of the 36 items are scored on a 3–6 point Likert scale. Scaling for different questions includes ranges from excellent to poor; limited a lot to not limited at all; not at all to extremely; and others. A higher score reflects a better health-related quality of life |
| General Health Questionnaire – 28 (GHQ–28) | A self-administered screening test, designed to identify short-term changes in mental health. The most popular of the GHQ, it has 28 questions, 7 in each subscale of depression, anxiety, social dysfunction, and somatic symptoms | Four subscores as well as a total score are obtained. The higher the score, the more severe the condition. A 4-point scoring system ranges from a "better/healthier than normal" option, through a "same as usual" and a "worse/more than usual" to a "much worse/more than usual" option |
| Hospital Anxiety and Depression scale (HADS) | A 14-item questionnaire designed to identify clinical depression and anxiety. 7 items conceptually assess depression and 7 items were derived from psychic manifestations of anxiety neurosis | Overall level of severity of each mood on a 4-point scale (0–3). A score of 8 is clinically significant, a score of 11 or more is highly clinically significant |
| Beck Depression Inventory (BDI) | A measurement of clinical depression with 21 statements regarding a symptom associated with depression (e.g., appetite, mood, sense of failure) | Scores range from 0, indicating the absence of the particular symptom, to 3 for most severe |
| Profile of Mood States (POMS) | A self-report designed to measure 6 dimensions of mood, which include: tension–anxiety; depression–dejection; anger–hostility; vigour–activity; fatigue–inertia; and confusion–bewilderment. It consists of 65 short phrases describing feeling and mood, with respondents asked to indicate mood reactions for the "past week including today" or for shorter periods such as "right now" | A 5-point Likert type scale ranging from 0 for no mood reaction to 5 for extreme mood reaction |
| University of Wales Institute of Science and Technology (UWIST) Mood adaptive checklist (UMACL) | A measurement of mood with 4 subscales: hedonic tone, anger, tense arousal, and energetic arousal. Except for anger, which only has positively loaded items, each one is made up of a combination of positively and negatively loaded items | The final score is the result of adding the positively loaded answers and subtracting the negatively loaded answers |
| Nottingham Health Profile (NHP) | Generic health-related quality-of-life measure made up of 38 items that can be used to produce scores for 6 domains of health, including: physical mobility (8 items), pain (8 items), social isolation (5 items), emotional reactions (9 items), energy (3 items), and sleep (5 items) | Yes/no answers and domain scores ranging from 0 to 100 Mean score is calculated across all items within each domain. Overall score is the mean across all items. The higher the score the greater the health problem |
| Functional Outcomes of Sleep Questionnaire (FOSQ) | A sleep-specific functional measure designed to evaluate the impact of sleep disorders and excessive sleepiness. 35 items represent 5 subscales: activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcome | Individual scores of each subscale are obtained and summated to produce a global score. The lower the score the greater the dysfunction as a result of sleepiness. 4 levels of response: no difficulty, a little, moderate, or extreme plus non-participation. Scored on a 5-point Likert scale |
| Cognitive performance measures | ||
| SteerClear (SC) | A computer program designed to simulate a long, mundane highway drive and to characterise the decrements in driving ability. The person is required to avoid obstacles that randomly appear on a 2-lane highway by pressing a single computer key. Performance on this 30-minute task is reflected by the number of obstacles passed and the number hit | Reducing the number of obstacles hit reflects improved vigilance |
| Trailmaking B tests (TMT-B) | A test for broad cognitive performance that uses the connect-a-dot concept requiring the person to draw lines from circle to circle to consecutively link numbers and letters in the quickest time possible | Better cognitive performance is indicated by a reduction in score, which reflects the time taken to complete the task |
| Digit Symbol Substitution (DSS) | Cognitive speed is tested by matching individually presented symbols to their numbers using a reference key | Improved speed of performance is reflected by an increased score |
| Paced Auditory Serial Addition Task – 2 second timing (PASAT–2) | A test of auditory attention and concentration by evaluating the time taken to add up numbers presented every 2 seconds | An increase in the score indicates improved ability to maintain concentration under distraction |
Incidence/ Prevalence
The Wisconsin Sleep Cohort Study (>1000 people; mean age 47 years) in North America found prevalence rates for an AHI of more than five episodes an hour of 24% in men and 9% in women, and for OSAHS with an index greater than five episodes an hour plus excessive sleepiness of 4% in men and 2% in women. There are international differences in the occurrence of OSAHS, of which obesity is considered to be an important determinant. Ethnic differences in prevalence have also been found after adjustment for other risk factors. Little is known about the incidence in resource-poor countries.
Aetiology/ Risk factors
The site of upper airway obstruction in OSAHS is around the level of the tongue, soft palate, or epiglottis. Disorders that predispose to either narrowing of the upper airway or reduction in its stability (e.g., obesity, certain craniofacial abnormalities, vocal cord abnormalities, enlarged tonsils, and enlarged tongue) have been associated with an increased risk of OSAHS. It has been estimated that a 1 kg/m2 increase in BMI (3.2 kg for a person 1.8 m tall) leads to a 30% increase (95% CI 13% to 50%) in the relative risk of developing abnormal sleep-disordered breathing (AHI 5 or more episodes/hour) over a period of 4 years. Other strong associated risk factors include increasing age, and sex (male to female ratio is 2:1). Weaker associations include menopause, family history, smoking, and night-time nasal congestion.
Prognosis
The long-term prognosis of people with untreated severe OSAHS is poor quality of life, likelihood of motor vehicle accidents, hypertension, and possibly CVD and premature mortality. Unfortunately, the prognosis of treated OSAHS is unclear. The limitations in the evidence include bias in the selection of participants, short duration of follow-up, and variation in the measurement of confounders (e.g., smoking, alcohol use, and other cardiovascular risk factors). Treatment is widespread, making it difficult to find evidence on prognosis for untreated OSAHS. Observational studies support a causal association between OSAHS and systemic hypertension, which increases with the severity of OSAHS (OR 1.21 for non-severe OSAHS to 3.07 for severe OSAHS). OSAHS increases the risk of motor vehicle accidents three- to sevenfold. It is associated with increased risk of premature mortality, CVD, and impaired neurocognitive functioning.
Aims of intervention
To minimise or eliminate symptoms of daytime sleepiness; to improve vigilance and quality of life; to reduce or abolish the increased risk of motor vehicle accidents and cardiovascular events; to enhance compliance with treatment; to minimise adverse effects of treatment.
Outcomes
Mortality; symptom severity (including daytime sleepiness, intermediate outcomes, cognitive performance, and quality of life); morbidity: for example, road traffic accidents, hypertension, changes in blood pressure, stroke, cardiac failure, and ischaemic heart disease; compliance: hours of usage of treatment; adverse effects. Here, we have included daytime sleepiness, intermediate outcomes, cognitive performance, and quality of life under symptom severity: details of validated outcome measures for daytime sleepiness, quality of life, and cognitive performance are listed in table 3 . Daytime sleepiness is measured using subjective and objective measures, such as the Epworth Sleepiness Scale, Multiple Sleep Latency Test, and Maintenance of Wakefulness Test (see table 3 ). Intermediate outcomes: Measures of the degree of disturbed breathing during sleep, such as the number of apnoeas and hypopnoeas an hour (AHI), the frequency of arousals, and the degree of sleep fragmentation. Quality of life: General measures such as the Medical Outcomes Study: 36-item Short Form Health Survey (SF-36) and the General Health Questionnaire; measures of mood, such as the Hospital Anxiety and Depression Scale, the Beck Depression Inventory, and the Profile of Mood States; measures of energy and vitality such as the SF-36 energy scale, the UWIST Mood Adjective Checklist, and the energy and vitality scale of the Nottingham Health Profile. Disease-specific quality-of-life measures include the Functional Outcomes of Sleep Questionnaire (see table 3 ). Cognitive performance measures: Steer Clear, Trailmaking Test B, Digit Symbol Substitution, and Paced Auditory Serial Addition Task — 2-Second Timing (see table 3 ).
Methods
Clinical Evidence search and appraisal May 2008. The following databases were used to identify studies for this systematic review: Medline 1966 to May 2008, Embase 1980 to May 2008, and The Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Clinical Trials 2008, Issue 2. Additional searches were carried out using the NHS Centre for Reviews and Dissemination (CRD) website — for the Database of Abstracts of Reviews of Effects (DARE) and the Health Technology Assessment (HTA) database. We also searched for retractions of studies included in the review. Abstracts of the studies retrieved from the initial search were assessed by an information specialist. Selected studies were then sent to the contributor for additional assessment, using predetermined criteria to identify relevant studies. Study design criteria for inclusion in this review were: published systematic reviews and RCTs, in any language. RCTs had to be least single-blinded where blinding was possible, and contain 20 or more individuals, of whom 80% or more were followed up. There was no minimum length of follow-up required to include studies. We excluded all studies described as "open", "open label", or not blinded unless blinding was impossible. In addition, we use a regular surveillance protocol to capture harms alerts from organisations such as the FDA and the MHRA, which are added to the reviews as required. Different RCTs have used slightly different definitions of OSAHS. Many of the identified studies were crossover RCTs. The results of the crossover trials should be viewed with caution, because effects of treatment before crossover may persist after crossover. To aid readability of the numerical data in our reviews, we round many percentages to the nearest whole number. Readers should be aware of this when relating percentages to summary statistics such as relative risks (RRs) and odds ratios (ORs). We have performed a GRADE evaluation of the quality of evidence for interventions included in this review (see table). The categorisation of the quality of the evidence (high, moderate, low, or very low) reflects the quality of evidence available for our chosen outcomes in our defined populations of interest. These categorisations are not necessarily a reflection of the overall methodological quality of any individual study, because the Clinical Evidence population and outcome of choice may represent only a small subset of the total outcomes reported, and population included, in any individual trial. For further details of how we perform the GRADE evaluation and the scoring system we use, please see our website (www.clinicalevidence.com).
Table.
GRADE Evaluation of interventions for Sleep apnoea.
| Important outcomes | Compliance, Morbidity, Mortality, Symptom severity | ||||||||
| Studies (Participants) | Outcome | Comparison | Type of evidence | Quality | Consistency | Directness | Effect size | GRADE | Comment |
| What are the effects of treatment for severe OSAHS? | |||||||||
| At least 10 RCTs (at least 536 people) | Symptom severity | Nasal CPAP versus placebo, sham CPAP, or conservative treatment | 4 | –2 | 0 | –1 | 0 | Very low | Quality points deducted for diagnostic uncertainty and incomplete reporting of results. Directness point deducted for uncertainty about comparators |
| At least 12 (at least 572 people) | Morbidity | Nasal CPAP versus placebo, sham CPAP, or conservative treatment | 4 | 0 | –1 | –2 | 0 | Very low | Consistency point deducted for conflicting results. Directness points deducted for inclusion of different range of disease severities and uncertainty about comparators |
| 2 (103) | Symptom severity | Oral appliances versus control oral appliance, no treatment, or placebo | 4 | –2 | 0 | –1 | 0 | Very low | Quality points deducted for sparse data and poor follow-up. Directness point deducted for inclusion of different range of disease severities |
| At least 16 RCTs (at least 637 people) | Symptom severity | Automatically titrated CPAP versus standard CPAP | 4 | 0 | –1 | –1 | 0 | Low | Consistency point deducted for statistical heterogeneity between studies. Directness point deducted for inclusion of different range of disease severities |
| At least 16 RCTs (at least 637 people) | Compliance | Automatically titrated CPAP versus standard CPAP | 4 | –1 | –1 | –2 | 0 | Very low | Quality point deducted for incomplete reporting of results. Consistency point deducted for statistical heterogeneity between studies. Directness points deducted for inclusion of different range of disease severities and definition of outcome |
| 4 (220) | Symptom severity | Bi-level positive airway pressure versus CPAP | 4 | 0 | 0 | –1 | 0 | Moderate | Directness point deducted for inclusion of multiple interventions |
| 4 (220) | Compliance | Bi-level positive airway pressure versus CPAP | 4 | 0 | –1 | –1 | 0 | Low | Consistency point deducted for conflicting results. Directness point deducted for inclusion of multiple interventions |
| 1 (24) | Symptom severity | Patient-titrated CPAP versus CPAP | 4 | –3 | 0 | 0 | 0 | Very low | Quality points deducted for sparse data, method of randomisation not reported, and high withdrawal rates |
| 1 (24) | Compliance | Patient-titrated CPAP versus CPAP | 4 | –3 | 0 | 0 | 0 | Very low | Quality points deducted for sparse data, method of randomisation not reported, and high withdrawal rates |
| 2 (162) | Symptom severity | CPAP plus humidification versus CPAP alone | 4 | –2 | 0 | 0 | 0 | Low | Quality points deducted for sparse data and incomplete reporting of results |
| 2 (162) | Compliance | CPAP plus humidification versus CPAP alone | 4 | –2 | 0 | 0 | 0 | Low | Quality points deducted for sparse data and incomplete reporting of results |
| 1 (72) | Symptom severity | CPAP plus educational/psychological intervention versus CPAP | 4 | –3 | 0 | 0 | 0 | Very low | Quality points deducted for sparse data, incomplete reporting of results, and uncertainty about significance of result |
| 5 (330) | Compliance | CPAP plus educational/psychological intervention versus CPAP | 4 | –1 | –1 | 0 | 0 | Low | Quality point deducted for incomplete reporting of results. Consistency point deducted for conflicting results |
| What are the effects of treatment for non-severe OSAHS? | |||||||||
| At least 5 RCTs (at least 326 people) | Symptom severity | Nasal CPAP versus conservative treatment, sham CPAP, or placebo | 4 | –1 | –1 | –1 | 0 | Very low | Quality point deducted for incomplete reporting of results. Consistency point deducted for conflicting results. Directness point deducted for inclusion of range of interventions |
| 9 (449) | Symptom severity | Oral appliances versus control oral appliance, no treatment, or placebo | 4 | 0 | –1 | –1 | 0 | Low | Consistency point deducted for conflicting results. Directness point deducted for diverse population |
| 10 (380) | Symptom severity | Oral appliances versus CPAP | 4 | 0 | –1 | –1 | 0 | Low | Consistency point deducted for conflicting results. Directness point deducted for diverse population |
| 1 (68) | Symptom severity | Adding oral appliances to conservative measures versus adding CPAP to conservative measures | 4 | –2 | 0 | –1 | 0 | Very low | Quality points deducted for sparse data and incomplete reporting. Directness point deducted for inclusion of range of interventions |
| 1 (68) | Morbidity | Adding oral appliances to conservative measures versus adding CPAP to conservative measures | 4 | –2 | 0 | –1 | 0 | Very low | Quality points deducted for sparse data and incomplete reporting. Directness point deducted for inclusion of range of interventions |
| 1 (34) | Symptom severity | Mechanical/physical alternatives (automatically titrated CPAP, bi-level positive airway pressure, patient-titrated CPAP, CPAP plus humidification) versus CPAP | 4 | –1 | 0 | –1 | 0 | Low | Quality point deducted for sparse data. Directness point deducted for inclusion of range of interventions |
| 1 (34) | Compliance | Mechanical/physical alternatives (automatically titrated CPAP, bi-level positive airway pressure, patient-titrated CPAP, CPAP plus humidification) versus CPAP | 4 | –1 | 0 | –1 | 0 | Low | Quality point deducted for sparse data. Directness point deducted for inclusion of range of interventions |
| 1 (93) | Symptom severity | CPAP plus educational/psychological interventions versus CPAP | 4 | –3 | 0 | 0 | 0 | Very low | Quality points deducted for sparse data, incomplete reporting of results, and high withdrawal rates |
| 1 (100) | Compliance | CPAP plus educational/psychological interventions versus CPAP | 4 | –2 | 0 | 0 | 0 | Low | Quality points deducted for sparse data and incomplete reporting of results |
We initially allocate 4 points to evidence from RCTs, and 2 points to evidence from observational studies. To attain the final GRADE score for a given comparison, points are deducted or added from this initial score based on preset criteria relating to the categories of quality, directness, consistency, and effect size. Quality: based on issues affecting methodological rigour (e.g., incomplete reporting of results, quasi-randomisation, sparse data [<200 people in the analysis]). Consistency: based on similarity of results across studies. Directness: based on generalisability of population or outcomes. Effect size: based on magnitude of effect as measured by statistics such as relative risk, odds ratio, or hazard ratio.
Glossary
- Apnoea
Absence of airflow at the nose and mouth for at least 10 seconds (duration based on consensus). It is sometimes defined indirectly in terms of oxygen desaturation index (impact on pulse oximetry saturation is measured as the number of occasions per hour when oxygen saturation falls by 4% or more). Apnoeas may be "central", in which there is cessation of inspiratory effort, or "obstructive", in which inspiratory efforts continue but are ineffective because of upper airway obstruction.
- Apnoea/hypopnoea index (AHI)
The sum of apnoeas and hypopnoeas per hour of sleep. Although the generally accepted cut-off point for "normal" is an index of five episodes per hour, there are several definitions of normal, of which at least four are applicable to the situation of sleep-disordered breathing: levels inside the range found in a "normal" (i.e., healthy) population; levels well removed from those found in a target disorder such as obstructive sleep apnoea-hypopnoea syndrome; levels not associated with a significant risk of disease and disability; and levels for which there is evidence of a significant benefit of treatment.
- Bi-level positive airway pressure (bi-level PAP)
Bi-level PAP devices apply a positive pressure to the upper airway through tubing and a face or nasal mask; however, the pressure during expiration (breathing out) may be adjusted separately from the pressure delivered during inspiration (breathing in). Bi-level PAP devices sense when an inspiratory effort is being made, and deliver a higher pressure during inspiration. When flow stops, the pressure returns to the baseline level. This positive pressure wave during inspirations unloads the diaphragm, decreasing the work of breathing. This form of ventilation has been used in long-term treatment of people with chronic respiratory failure because of neuromuscular problems or chest wall abnormalities.
- Cognitive behavioural therapy (CBT)
A form of psychological therapy that uses a range of techniques including examination and challenging of unhelpful thoughts, help with changing behaviours, and examination of underlying dysfunctional assumptions.
- Continuous positive airway pressure (CPAP)
This involves applying positive pressure from a blower motor to the upper airway through tubing and a soft nasal mask or a facemask. It provides a "pneumatic splint" to the upper airway. Because nasal delivery is the most common in the published literature, we refer to "nasal CPAP".
- Excessive daytime sleepiness (EDS)
A condition in which an individual has an overwhelming urge to fall asleep. People with excessive daytime sleepiness feel drowsy and tired, and often nod or doze easily in relaxed or sedentary situations, or fall asleep in situations where they need or want to be fully awake and alert. EDS can interfere with a person's ability to concentrate and perform daily tasks and routines. It can be measured in a sleep laboratory with a Multiple Sleep Latency Test (MSLT) or a Maintenance of Wakefulness Test (MWT), or with questionnaires such as the Epworth Sleepiness Scale (ESS) or Stanford Sleepiness Scale.
- Hypopnoea
A major reduction (>50%) in airflow at the nose and mouth for at least 10 seconds. A smaller reduction in airflow may be accepted as hypopnoea if it is associated with either electroencephalographic arousal or a reduction in oxygen saturation of at least 3% to 4%.
- Low-quality evidence
Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
- Moderate-quality evidence
Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
- Oral appliance
The term "oral appliance" is generic for devices placed in the mouth to change the position of the mandible, tongue, and other structures in the upper airway to reduce snoring or the upper airway obstruction of obstructive sleep apnoea-hypopnoea syndrome. Specific types are referred to as mandibular advancement devices or splints.
- Sleep-disordered breathing (SDB)
This condition includes both obstructive sleep apnoea-hypopnoea syndrome (OSAHS) and the upper airway resistance syndrome (UARS). OSAHS is defined by the presence of apnoeas (no airflow for 10 seconds or more) and hypopnoeas (markedly reduced airflow for 10 seconds or more), combined as the apnoea-hypopnoea index (AHI). UARS is defined by the presence of respiratory effort-related arousal events (RERAs). Features of SDB include snoring, witnessed episodes of absent breathing (apnoeas), abnormal breathing during sleep, nocturnal hypoxaemia, and abnormal sleep architecture. The increasingly accepted single measure of SDB is the respiratory disturbance index (RDI), which is the sum of AHI plus RERAs (and other respiratory events), expressed as the number of events per hour of sleep.
- Upper airway resistance syndrome (UARS)
Measurement of inspiratory effort by oesophageal pressure shows recurrent episodes of increased inspiratory effort that maintain stable ventilation but are associated with arousals and sleep fragmentation. These episodes are also referred to as respiratory effort-related arousal events (RERAs). More recent techniques for measuring nasal airflow can show changes consistent with upper airway resistance syndrome without the need for an oesophageal pressure catheter.
- Very low-quality evidence
Any estimate of effect is very uncertain.
Disclaimer
The information contained in this publication is intended for medical professionals. Categories presented in Clinical Evidence indicate a judgement about the strength of the evidence available to our contributors prior to publication and the relevant importance of benefit and harms. We rely on our contributors to confirm the accuracy of the information presented and to adhere to describe accepted practices. Readers should be aware that professionals in the field may have different opinions. Because of this and regular advances in medical research we strongly recommend that readers' independently verify specified treatments and drugs including manufacturers' guidance. Also, the categories do not indicate whether a particular treatment is generally appropriate or whether it is suitable for a particular individual. Ultimately it is the readers' responsibility to make their own professional judgements, so to appropriately advise and treat their patients. To the fullest extent permitted by law, BMJ Publishing Group Limited and its editors are not responsible for any losses, injury or damage caused to any person or property (including under contract, by negligence, products liability or otherwise) whether they be direct or indirect, special, incidental or consequential, resulting from the application of the information in this publication.
Contributor Information
Michael Hensley, University of Newcastle, Newcastle, NSW, Australia.
Cheryl Ray, Newcastle Sleep Disorders Centre, Royal Newcastle Hospital, Newcastle, NSW, Australia.
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