Fifteen men with severe OSA documented by standard nocturnal polysomnography comprised the group of patients. All were referred because of excessive daytime sleepiness, nocturnal breath cessation, or loud snoring. None had clinical or roentgenographic evidence of pulmonary disease.

Ten control subjects were recruited through advertisements seeking healthy overweight men. Most of these men were snorers. Volunteers with symptoms suggestive of sleep-disordered breathing, alcoholism, regular use of hypnotic medication, upper-respiratory- tract disorders, or cardiopulmonary disease were excluded. All control subjects also underwent standard nocturnal polysomnogra­phy.

All subjects gave informed written consent after explanation of the protocol, which was approved by the Clinical Investigation Committee of the Milton S. Hershey Medical Center of Pennsyl­vania State University. For entry into the study, we required all subjects to have a normal FEV/FVC ratio. Viagra Online Canadian Pharmacy


Spirometry was performed with a 10-L dry rolling-seal spirometer (Gould 5000 IV Computerized Pulmonary Function Lab). This system has a built-in capacitor to filter out electromechanical noise generated by one-way valves in the spirometer. The hot-wire anemometer flowmeter is linear and has an accuracy of ±0.1 Us and a flow-path resistance of less than 1.5 cm H20/L/s at a flow of 12 L/s. Subjects were seated for all studies. The single best values

for FVC and FEV, from a minimum of three spirograms were selected to report the FEV/FVC ratio. Serial maximal expiratory and inspiratory flow-volume curves were recorded on an X-Y plotter (Hiplot) having an accuracy of ±0.5 mm vertical and ±0.8 mm horizontal. The expiratory curve with the highest sum of FVC and FEV, and the inspiratory curve with the highest FIF50% were together selected for determination of FEF50%/FIF50% and in­spection for the presence of a sawtooth pattern. This appearance was defined as the presence of three or more consecutive symmetric peaks and troughs of similar appearance and no greater than 300 ml occurring at regular intervals between 25 percent and 75 percent of the vital capacity on either the expiratory or inspiratory sides of the flow^volume loop. Three pulmonologists, all blinded to the results of polysomnography; independently inspected each flow- volume loop for the sawtooth appearance, which was considered to be evident if at least two panel members agreed on its presence. Measurements of lung volume were performed with the helium dilution technique (accuracy ±3 percent) and reported as BTPS. Maximum voluntary ventilation was measured for 12 s and con­verted to liters per minute. Normal values for pulmonary (unction measurements were taken from standard reference sources. All PFTs were performed in accordance with standards of the American Thoracic Society.

Sleep Studies

All subjects underwent night-long polysomnography with routine placement of electroencephalographic, electro-oculographic, and electromyographic leads to identify sleep stages. Nasal/oral airflow was monitored with a thermistor and a capnograph mounted over the nose and mouth or with thermocouples. Respiratory effort was assessed with either thoracic and abdominal strain gauges or an inductive plethysmograph, and arterial oxygen saturation was monitored with an ear oximeter. Data were continuously recorded on a multichannel polygraph (Grass model 78D). Abnormal breath­ing events were characterized as apneas (10 s or longer of airflow cessation) or hypopneas (a decrement in airflow with a fall in oxygen saturation of 4 percent or more). Apneas were classified as central, obstructive, or mixed in accordance with standard terminology. The AI and AH I defined the mean number of abnormal breathing events per hour of sleep. All control subjects had an AHI less than 3.0.
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