Positional modification techniques for supine obstructive sleep apnea: A systematic review and meta-analysis

Summary

This review aimed to determine the effectiveness of positional modification techniques in preventing supine sleep, sleep-disordered breathing and other clinically important outcomes in patients with supine obstructive sleep apnea (OSA). Randomized controlled trials comparing positional modification techniques with any other therapy or placebo were included. Electronic searches of databases including CENTRAL, MEDLINE, CINAHL, Embase, and Web of Science up to April 2016 were performed. Meta-analysis was undertaken where possible. This comprehensive meta-analysis found benefit for positional modification techniques in those with supine OSA in terms of reduction in apnea-hypopnea index (AHI) and time spent supine. Whilst positional modification techniques were effective in terms of a reduction in AHI, continuous positive airway pressure (CPAP) was more effective than these techniques. A reliable diagnosis of supine OSA should be considered, and further research is required on patient-centred outcomes including comfort, barriers to adherence, cost-analysis, and long term outcomes including the effect on cardiovascular disease, the metabolic syndrome, and insulin resistance.

Introduction

Obstructive sleep apnea (OSA) is characterised by repetitive collapse of the upper airway during sleep, resulting in increased arousals, sleep fragmentation and decreased oxygenation [1]. It affects almost one fifth of the adult population [2] and may lead to cognitive dysfunction including excessive sleepiness, decreased concentration [3], and systemic effects including hypertension [4], insulin resistance [5], cardiac arrhythmias, and increased mortality [6], [7]. Current clinical criteria for the diagnosis of OSA are accepted as a total apnea-hypopnea index (AHI) ≥15 events/h without symptoms or AHI ≥5 events/h with symptoms [8], [9].

First line treatment for OSA includes lifestyle modification such as weight loss, but the mainstay of therapy is continuous positive airway pressure (CPAP) [10]. CPAP has been shown to be highly effective at resolving OSA, reducing daytime sleepiness and improving quality of life [11]. Unfortunately not all patients can tolerate or accept CPAP and only half of patients prescribed CPAP continue to use it in the long term [12]. A significant proportion of others remain persistently sleepy despite treatment [13]. In many cases, alternative therapies are recommended, including mandibular advancement splints and surgical interventions [10].

There are, however, variable clinical phenotypes of OSA, the most common of which is that of supine position related OSA, where OSA is more severe in the supine compared to lateral sleeping position. The definitions used to classify supine OSA are varied, although there are two generally accepted definitions of supine OSA: supine predominant OSA, and supine isolated OSA [14]. ‘Supine predominant’ OSA is classified as total AHI ≥5 events per hour with respiratory events occurring at twice the frequency in the supine compared to the non-supine sleeping positions. Supine predominant OSA is very common, with approximately 60% of patients with OSA having supine predominant OSA [15]. ‘Supine isolated’ OSA is defined as OSA where the ratio of respiratory events in the supine to non-supine positions is greater than 2:1 and the AHI in non-supine positions is <5 events per hour. Supine isolated OSA is present in approximately 32% of OSA patients presenting to sleep clinics [14]. Recently, Frank and Ravesloot have proposed a new standardized definition of positional OSA – the Amsterdam positional OSA classification (APOC). The APOC stratifies patients by the AHI in their best and worst sleeping positions, as well as by the percentage of total sleep time spent in each in order to better identify which patients will benefit from positional modification therapy. Currently there are no randomized trials which have used this new classification system, although it holds promise for future research and to potentially determine what proportion of supine OSA requires treatment [16], [17].

Compared to non-positional OSA patients, those with supine OSA are more likely to be younger, less obese, have less severe OSA, are more likely to snore, and have less objective daytime sleepiness [14]. They are also less likely to adhere well with CPAP treatment [18]. Treatment options for supine OSA include usual treatments for OSA such as CPAP, but also therapies that encourage patients to avoid the supine position and spend more time in lateral sleep ∗[10], ∗[14]. Avoiding the supine sleeping position is proposed to be particularly relevant for patients with supine isolated OSA, whereby preventing supine sleep is predicted to “cure” OSA. There is no standard positional modification therapy and many commercial options are available, including binders, backpacks [19], tennis balls attached to vests or braces [20], and electrical sensors with alarms or vibratory components that alert the patient to move from the supine position [21]. Other options include pillows and patient-designed tennis ball inserts.

Position modification therapy (PMT) may potentially be preferred over other treatments by some patients due to lower cost, ease of use and possible increased patient comfort [19]. A number of studies have assessed the short term effectiveness of position modification therapy for supine predominant OSA, but all of these studies have involved only small numbers of subjects and may therefore potentially be underpowered. A meta-analysis in 2014 demonstrated that CPAP is superior to PMT with respect to improving the AHI and oxygen saturation level, however there were important limitations to this study. Three studies were incorporated into the meta-analysis [19], [20], [22], however in one of the studies, non-parametric data were extrapolated to create a mean and standard deviation [19]. Furthermore, that analysis was not extended to compare PMT with an inactive control [23].

Therefore, it remains unclear how effective position modification therapy truly is. Given this, we conducted a systematic review and meta-analysis with the aim of assessing the overall effectiveness (versus no therapy) and comparative effectiveness (versus CPAP) of position modification therapy with respect to: a) success at maintaining the non-supine sleeping position, b) improvement in OSA severity and sleep quality, and c) improvement of clinical outcomes.