EFFICACY OF AUTOMATIC CONTINUOUS POSITIVE AIRWAY PRESSURE THERAPY THAT USES AN ESTIMATED REQUIRED PRESSURE IN THE TREATMENT OF THE OBSTRUCTIVE SLEEP-APNEA SYNDROME

Background: Continuous positive airway pressure (CPAP) is effective th erapy for the obstructive sleep apnea syndrome (OSAS). Automatic CPAP devices continuously adjust the positive pressure to the required leve ls. Objective: To determine the efficacy of an automatic CPAP machine used with an estimated reference pressure value. Design: A before-and- after, single-blind trial in which patients were randomly allocated to one of three modes of CPAP administration. Setting: Referral-based sl eep center in a public health care institution. Patients: 36 outpatien ts with OSAS. Intervention: Continuous positive airway pressure was gi ven at a conventional fixed pressure (group 1), automatic CPAP was giv en at a measured reference pressure (group 2), and automatic CRAP was given at an estimated reference pressure (group 3). In group 1, the ef fective pressure was determined during a titration sleep study. In gro ups 2 and 3, the pressure interval was allowed to vary from 4 cm H2O b elow reference pressure to 3 cm H2O above reference pressure. In group 3, the estimated value of the reference pressure was determined accor ding to individual anthropometric characteristics. Measurements: Sleep studies were performed and measurements of diurnal sleepiness were ob tained at each visit. Results: Sleep and breathing disorders and hyper somnolence were alleviated similarly in the three groups. The apnea hypopnea index remained abnormal in one patient in group 3 for whom th e reference pressure had been underestimated. A strong negative correl ation was found between the percentage of time spent below reference p ressure during CPAP and the difference between the effective and estim ated pressures. Conclusion: Automatic CPAP can be used with an estimat ed reference pressure without doing a titration sleep study. The posit ive pressure trend can be used to determine whether treatment failure is caused by an inadequate pressure setting and to determine the amoun t of pressure to apply.