Details of HTA project
Last updated: 15 July 2008 - Next update due: 22 July 2008
Research type: |
NICE Technology Assessment Report (TAR) |
Project title: |
Continuous positive airways pressure (CPAP) for the treatment of obstructive sleep apnoea/hypopnoea syndrome (OSAHS) |
Project ref: |
06/57/01 |
Cost: |
This project has been commissioned by the HTA programme on behalf of the National Institute for Health and Clinical Excellence on a call-off contract basis. |
Chief Investigator : |
NHS Centre for Reviews and Dissemination (CRD), University of York |
Start Date: |
November 2006. |
Publication date: |
October 2008. This project is at the editorial review stage. Delays in the review process can cause the forecast publication date to be delayed. |
Plain English Summary |
Obstructive sleep apnoea-hypopnoea syndrome (OSAHS) is a condition where patients experience repetitive apnoeas due to partial or complete collapse of the pharyngeal airway during sleep, which leads to interrupted sleep and excessive daytime sleepiness. This narrowing or closure of the airway is due to a decrease in the muscle-tone in the muscles supporting the airway as part of the sleep process itself. Complete closure or obstruction stops airflow (apnoea) and partial obstruction decreases airflow (hypopnoea). Both events result in a brief awakening from sleep to restore normal breathing. When the patient falls asleep the closure of the airway occurs again resulting in many episodes of brief awakening during the night. As a result, the quality of sleep is affected and this causes excessive daytime sleepiness, and reduced cognitive performance. Therefore mood and quality of life can be adversely affected. There is evidence that OSAHS is associated with high blood pressure, cardiovascular disease and increased risk of car accidents. Continuous positive airway pressure (CPAP) is increasingly viewed as the most appropriate treatment for the moderate to severe form of the disease though there are wide variations in the provision of this treatment across the UK and its cost-effectiveness is unclear. CPAP devices are small, electric pumps which deliver air to the nose or mouth via a hose and soft plastic mask. The pressure, which can be fixed or autotitrated (auto-CPAP), opens up the airway from the nose down, preventing the soft tissue from collapsing. The appropriateness of CPAP for mild disease is unclear and dental devices may be an alternative treatment. Dental devices hold the tongue or jaw bone forward and help to keep the upper airway enlarged. Other treatment options include behavioural modification such as losing weight (as people who are overweight are more likely to have OSAHS), avoiding alcohol before sleep, improving night-time routines and altering sleep position. These are considered important for all OSAHS patients even where CPAP or dental devices are being used. The primary objectives of this project are to determine the clinical effectiveness, safety, and cost-effectiveness of continuous positive airway pressure (CPAP) devices for the treatment of obstructive sleep-apnoea-hypopnoea syndrome (OSAHS) compared with best supportive care, placebo and dental devices. |
Abstract: |
The primary objectives are to determine the clinical effectiveness, safety, and cost-effectiveness of continuous positive airway pressure (CPAP) devices for the treatment of obstructive sleep-apnoea-hypopnoea syndrome (OSAHS) compared with best supportive care, placebo and dental devices. Obstructive sleep apnoea-hypopnoea (OSAH) is characterised by repeated, intermittent collapse and obstruction of the pharyngeal airway during sleep. Airway collapse can be complete, with total obstruction of the airway lumen and no respiratory airflow (apnoea), or partial with reduced respiratory airflow (arbitrarily often defined as at least a 50 % reduction - a hypopnoea). Pharyngeal patency depends on dilator muscles which contract during each inspiration to prevent the upper airway being closed by suction. The upper airway collapses due to falling muscle tone in the dilating muscles with sleep, leading to narrowing or total obstruction. This may result in brief awakening from sleep caused by increased respiratory effort. Recurrent arousal required to restore airway patency results in fragmentation of normal sleep architecture and a reduction in sleep quality. When obstructive sleep apnoea-hypopnoea leads to excessive daytime sleepiness, this is known as OSAHS. Prevalence of detectable OSAHS has been estimated at 4-6% in males (30-65 years old), and approximately 1% in women of the same age. Prevalence is thought to be lower among those in younger and older age groups. Severe OSAHS is also associated with obesity; around 50% of OSAHS patients have body mass indices of greater than 30kg/m2. Since 1980 the prevalence of obesity has nearly trebled in the UK and is continuing to increase, which has implications for prevalence of OSAHS. Genetic influences, aspects of cranio-facial shape and pharyngeal pathology (such as enlarged tonsils) may also contribute to the pathogenesis of OSAHS. Prevalence may be higher amongst some ethnic groups; among Asians the risk of developing OSAHS is thought to be related to both craniofacial morphology and obesity, whilst among Hispanics, American Indians and Pacific Islanders the increased prevalence is largely explained by increased obesity. Some patients with OSAHS have significant co-comorbidities such as hypertension, diabetes, heart failure and brain disease such as stroke. Heart disease and brain disease, (including stroke and dementia), can themselves induce 'central' (that is breathing control system mediated) sleep apnoea syndromes such as Cheyne-Stokes breathing. These central sleep apnoea syndromes can cause complexities in exact sleep apnoea diagnosis and so are considered outside the remit of the proposed review. Untreated, OSAHS is associated with increased daytime sleepiness, deterioration in cognitive functions, especially those requiring concentration, changes in mood or personality, and hypertension.Importantly, symptoms of daytime sleepiness and impaired concentration from untreated OSAHS also pose a significant increased risk of automobile accidents and injury in the workplace. Furthermore, OSAHS has also been associated with a reduction in quality of life, including impairment in spousal/partner relationships. Diagnosis of OSHAS is usually based on recordings of multiple physiological signals during sleep (polysomnography, PSG). These include the apnoea/hypopnoea index (AHI), and repetitive oxygen desaturation indices. The AHI is the frequency of apnoeas and hypopnoeas per hour of sleep; a typical cut-off for positive diagnosis is between 5 and 10 per hour. The AHI is also used to categorise severity. Whilst definitions regarding the severity of OSAHS vary between sleep centres, recent recommendations for cut-offs suggest that mild OSAHS is defined as AHI 5-15/hr, moderate OSAHS is defined as AHI 15-30/hr, and severe OSAHS is defined as AHI>30/hr.22 Oxygen desaturation is calculated as the number of events causing a drop in arterial oxygen saturation per hour. Typically a diagnostic cut-off of >4% drop is used, with thresholds approximating hypoxic dips per hour of 5-10 (mild), 10-30 (moderate), and greater than 30 (severe). None of these measures take into account the severity of other symptoms such as daytime sleepiness. This is considered important as the daytime consequences of OSAHS are often of more concern to the patient than nocturnal events. Several tools are available for measuring sleepiness both subjectively and objectively. The Epworth Sleepiness Scale (ESS) is the most frequently used assessment of daytime sleepiness. This short questionnaire measures the general level of daytime sleepiness based on the subjective probability of falling asleep in a variety of situations. Other, more direct, measures of daytime sleepiness include the Multiple Sleep Latency Test (MSLT), which measures the propensity to fall asleep in favourable conditions, and the Multiple Wakefulness Test (MWT), which measures the capacity to remain awake in conditions supposedly ideal for falling sleep. Both these measures are assessed using a polysomnogram. An additional measure is the Osler test, a simplified version of the MWT, which uses a behavioural test rather than electroencephalograph recordings to define sleep onset. The mainstay of medical treatment of OSAHS is administration of continuous positive airway pressure (CPAP) during sleep, although there are wide variations in the provision of treatment across the United Kingdom. CPAP devices are small, electric pumps which deliver air to the nose or mouth via a hose and soft plastic mask. The pressure, which can be fixed or autotitrated (auto-CPAP), opens up the airway from the nose down, preventing the soft tissue from collapsing. Fixed CPAP devices deliver air at a fixed optimal pressure, usually identified by earlier observation and titration, during sleep, while auto-CPAP devices increase pressure as needed to maintain airway patency or decrease pressure if no events are detected over a set period of time. As the minimum effective pressure delivered is automatically adjusted in auto-CPAP devices, the mean pressure is often lower than the optimal fixed pressure in CPAP units. Failure to comply with treatment in standard CPAP devices has been reported to be low in clinical practice.Reasons for discontinuation primarily relate to physical discomfort, nasal dryness and congestion, difficulty adapting to the pressure, dislodgment during sleep, and the social consequences of using the unit. One strategy to reduce side-effects has been the use of humidifiers, which have been shown to prevent upper airway dryness associated with CPAP use. Alternative treatment includes the use of dental appliances, although these are generally only used in individuals with mild to moderate OSAHS. Dental devices maintain the patency of the pharyngeal airway and prevent the lumen from collapsing during sleep by holding the tongue or mandible forward, thereby enlarging the posterior airspace. There are several different modifications of the technology though for the purposes of the proposed review they will be treated as one class. Evidence for lifestyle modification as an efficacious treatment is weak, however, lifestyle management is often recommended as an adjunct to treatment. Other treatments, such as surgery or drugs, are rarely used, and recent Cochrane reviews do not support their use for treatment of OSAHS. A number of previous reviews have looked at the use of CPAP devices for the treatment of OSAHS. The most comprehensive of these, reported that CPAP was effective in reducing symptoms of sleepiness, and improved quality of life in individuals with moderate and severe OSAH. The review also found that CPAP was more effective than oral devices in reducing respiratory disturbances, although no difference was shown between the treatments groups on subjective outcomes. Two previous cost-effectiveness analyses have found CPAP for moderate to severe disease more effective and more costly than no CPAP, though neither study was undertaken in the UK. THE HTA PROGRAMME COMMISSIONED THIS TECHNOLOGY ASSESSMENT REPORT ON BEHALF OF THE NATIONAL INSTITUTE FOR HEALTH AND CLINICAL EXCELLENCE. |
NRR* number, if applicable: |
N0484190627 (*National Research Register) |
Project Protocol: |
Project protocol not available |
URL of this page: |
http://www.hta.ac.uk/1592 |
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