Auto-adjusting versus Fixed Pap Introductions Obstructive Sleep Apnoea Syndrome (osas) Is a Common Medical Disorder Affecting 2% to 4% of the Adult Middle-aged

OBSTRUCTIVE SLEEP APNOEA SYNDROME (OSAS) IS A COMMON MEDICAL DISORDER AFFECTING 2% TO 4% OF THE ADULT MIDDLE-AGED POPULATION.1 Recent studies have suggested that even patients with mild breathing abnormalities during sleep (apnoea-hypopnoea index, [AHI] < 15) may have associated hypertension,2 neurocognitive deficits,3 and excessive daytime sleepiness leading to an increased risk of motor vehicle accidents.4 Continuous positive airway pressure5 (CPAP) has become the standard treatment for OSAS, particularly in moderate to severe cases, and has also been shown to produce significant benefits in patients with mild disease.6,7 However, despite its efficacy, nasal CPAP is not fully accepted by all patients.8 Initial acceptance rates are generally in the region of 80%, and nightly use averages about 5 hours per night,9 although some studies have shown hourly usage rates as low as 3 hours per night.10 Furthermore, compliance with CPAP has been shown to be lower in patients with mild to moderate OSAS, particularly when not associated with daytime sleepiness.11 Auto-adjusting positive airway pressure (APAP) devices are a more recently developed alternative modality of therapy that continuously adjust the pressure to the optimal level, and many studies have shown the mean nightly pressure to be lower on APAP, as compared with fixed-pressure devices.12,13 Thus, it is possible that APAP devices could increase compliance by reducing side effects associated with air leaks and noise at higher pressures. To date, many studies have shown that APAP can control OSAS as effectively as CPAP, but whether these devices improve patient compliance is still not clear.14 However, a recent report has shown improved compliance with APAP therapy in patients with OSAS who require high pressure levels on CPAP to control their condition.15 In our clinical experience, patients with mild to moderate OSAS (AHI < 30 events per hour of sleep) are less likely to tolerate nasal CPAP therapy than are those with severe OSAS. We hypothesized that the lower treatment pressures delivered by APAP could improve compliance, as compared with CPAP, in patients with mild to moderate disease. Thus, in a randomized crossover study, we compared treatment efficacy, compliance, and device preference between APAP and CPAP therapy in patients with mild to moderate OSAS. The primary endpoint was patient compliance and device preference at the end of the initial 4-month crossover study. A secondary endpoint was long-term compliance with the selected device after 18-months of therapy.