All of the six men previously reported underwent jejeuno-ileal bypass surgery for weight reduction. One man died several weeks after surgery. Four of the five surviving affected subjects agreed to be restudied after weight loss. All were studied approximately two years after surgery. They were interviewed with special reference to symptoms suggestive of sleep disorders or cardiorespiratory disease. Two of the four underwent complete studies of pulmonary function, including spirometry, pulmonary volume by nitrogen washout, single-breath carbon monoxide diffusing capacity, and arterial blood gas analysis. The results of these studies were compared to published normal values.
All subjects were monitored during a single night of sleep with methods similar to those used in previous studies from our institution. No sedation was given on the night of the study. Continuous oxygen saturation was measured with an ear oximeter (Hewlett-Packard 47201-A) and was recorded on a multichannel recorder (Narco Biosystems physiograph DMP-48). Oral and nasal temperatures were sensed with thermistors (Grass) clipped to one nostril and lip. Air flow was qualitatively reflected by change in temperature sensed by these thermistors. Motion of the chest was sensed by impedance plethysmographic studies with surface electrodes (Narco) and an impedance pneumographic coupler. Ibese electrodes were placed at the point of maximum motion of the wall of the chest during quiet breathing. Electroencephalograms and electrooculograms were simultaneously recorded on an electroencephalographic and polygraphic recording system (Grass 79D). The tracings thus obtained were analyzed by an experienced sleep technician according to the system of Agnew and Webb. Sleep was staged on one-minute intervals. The sleep period time was defined as the total time between falling asleep (onset of electroencephalographic stage 1) and awakening.
A research technician was at the bedside during the entire period of sleep, noting the patient’s behavior and recording this on a sleep tracing. Timing of events was recorded on the tracing, and each tracing was reviewed in detail and correlated with stages of sleep.
Apnea was noted when flow ceased at the nose and mouth for 10 seconds or longer. Since an esophageal balloon was not used, no differentiation between central and obstructive apnea (http://patient.info/doctor/obstructive-sleep-apnoea-syndrome-pro) was made. Hypopnea was noted if flows at the nose and mouth decreased, with or without concomitant decrease in motion of die chest wall, and desaturation occurred. Desaturation was defined as a fall of at least 4 percent from baseline saturation.
Analyses of the difference in pre- and post-weight loss events were done by the Wilcoxon sign-rank test.