RELATIVE OCCURRENCE OF FLOW LIMITATION AND SNORING DURING CONTINUOUS POSITIVE AIRWAY PRESSURE TITRATION

Objectives: To examine the relative temporal appearance of flow Limita tion and snoring during continuous positive airway pressure (CPAP) tit ration, compare their sensitivity as indicators of airway obstruction, and assess their relative utility as feedback variables for automatic titration of CPAP. Design: Retrospective review of data. Setting: Uni versity teaching hospital. Patients: Fifty-three patients diagnosed as having obstructive sleep apnea or upper airway resistance syndrome un dergoing CPAP titration. Measurements and results: We used a prototype automatic CPAP device that adjusts pressure in response to apnea, sno ring, and/or flow limitation. The present study takes advantage of the frequent automatic decreases in pressure from a therapeutic level, as well as any technician-initiated decreases in pressure. We tabulated, for each pressure decrease of >0.4 cm H2O, the occurrences of snoring alone, flow limitation alone, or simultaneous appearance of both. Of 2,177 automatic pressure decreases, 64% resulted in flow limitation al one, 8% in snoring alone, and 22% in the simultaneous occurrence of bo th, Overall, 86% of decreases resulted in flow limitation alone or wer e simultaneous with snoring, whereas 30% of decreases resulted in snor ing alone or were simultaneous with flow limitation. In 10 of 35 patie nts, snoring alone occurred in > 10% of the pressure decreases. In all but 5 of 133 manual pressure decreases, flow limitation developed at or above the pressure at which snoring developed. Conclusions: While d etection of snoring occasionally provided additional information, over all flow limitation was the earliest indicator of obstruction during d ecreases in CPAP.