LOAD DETECTION IN SUBJECTS WITH SLEEP-INDUCED UPPER AIRWAY-OBSTRUCTION

Respiratory flow-resistive load detection in obese patients has been s hown to be impaired. We tested the hypothesis that there is no differe nce in inspiratory flow-resistive load detection measured in nonobese obstructive sleep apnea patients, nonobese snorers, and normal control subjects. Eleven male obstructive sleep apnea patients and seven mate snorers were investigated and compared with 10 normal male control su bjects. Severely obese patients (body mass index, BMI > 35 kg/m(2)) we re excluded. Patients were investig ated by nocturnal polysomnography with measurement of esophageal pressure (Pes). Awake pulmonary functio n tests were performed before the investigation. Airway resistance (Ra w) and lung volumes were measured with plethysmography. Resistive load s were investigated according to Tapper and associates (13) and Killia n and associates (12). Resistances were applied for the duration of on e inspiratory cycle and a minimum of two breaths allowed between each resistive load. Six different resistances plus background shams were p resented 10 times in random order. Flow, pressure, and subject respons e were recorded with a calibrated multichannel recorder. Subjects sign aled detected changes of inspiratory resistance with a hand-held signa ling device. The probability of detecting a particular resistance was calculated as the ratio of correct identification to the number of pre sentations (i.e., 10). The resistance corresponding to a 0.5 probabili ty of detection was determined. The Weber fraction (wf) was calculated as Delta R/R(apparatus) + Raw. There were no differences between nono bese subjects and controls in terms of resistive load detection.