Dose-response relationship between CPAP compliance and measures of sleep apnea severity

Obstructive sleep apnea is a prevalent condition with serious medical and psychosocial consequences. Nasal continuous positive airway pressure (CPAP) is the treatment of choice and has been shown to reduce the frequency of nocturnal respiratory events, improve sleep architecture, and decrease daytime sleepiness. However, little is known about the dose-response relationship between CPAP compliance and measures of sleep apnea severity. This study examined the relationship between level of CPAP compliance and change in polysomnographic measures of sleep apnea severity.

Twenty-three CPAP-naive OSA patients were studied. None had other major medical illnesses or were receiving antihypertensive medication. Sleep apnea variables were measured at baseline and after 1 week of treatment. Objective CPAP compliance was measured nightly and was defined as the average number of hours of use per night.

Higher rates of CPAP compliance were linearly associated with significant reductions in the respiratory disturbance index (R=0.49, P=0.017), the oxygen desaturation index (R=0.48, P=0.029), and the arousal index (R=0.51, P=0.016).

These data suggest that increased CPAP compliance is linearly associated with reductions in sleep apnea severity such that greater reductions in apnea were seen with increased CPAP use. It should be noted that all patients were reasonably compliant (i.e. >4h CPAP use/night) and that even within this range of reasonable compliance, there was a significant benefit with more as opposed to less compliance. These findings offer support to the current recommendation that CPAP be used during the total time in bed to optimize treatment of polysomnographic measures of sleep apnea.