CONTINUOUS VERSUS BILEVEL POSITIVE AIRWAY PRESSURE FOR OBSTRUCTIVE SLEEP-APNEA

Recent objective studies demonstrate relatively low hours of nightly u se during nasal continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea (OSA). Patients frequently complain of dyspne a or discomfort during CPAP use, especially during expiration (against the continuous pressure), which may be a reason for the tow hours of use. We hypothesized that with decreased expiratory pressure, hours of nightly use would increase. Therefore, we randomized 83 OSA patients to receive either continuous or bilevel positive airway pressure when expiratory pressure is lower. To document objectively the effective us e of either therapy, we built and installed elapsed-time and mask pres sure sensors in the patients' positive airway pressure units. A total of 62 patients were evaluable and followed for 1 yr. Of these, 26 rece ived bilevel and 36 CPAP pressures. The machine timers measured accumu lated ''machine-on'' time, and the mask pressure sensor recorded the t otal time in which the mask pressure was within 2 cm H2O of the effect ive pressure (pressure shown to eliminate 95% of the obstructive apnea s during a full night of polysomnography). The mean machine timer hour s of CPAP were 5.0 +/- 0.19 SEM and 4.9 +/- 0.23 SEM during bilevel th erapy (p NS) over a 12-mo period. The pressures required during CPAP o r bilevel therapy were not different between high and low hourly users . Effective use, the percentage of time that the machine was running a nd the prescribed pressure was being delivered, was 80% in CPAP and 82 % in the bilevel users (p NS). Both groups had equal complaints with r egard to mask discomfort, machine noise, and nasal stuffiness. In conc lusion, no difference in average hours of use during 12 mo of CPAP and bilevel therapy was identified in the OSA patients studied.