The four subjects averaged 36 years of age. Prior to weight loss, their mean body weight was 231 kg, or 341 percent of ideal body weight, derived from standard tables. At the time of restudy, their mean weight was 123 kg, or 176 percent of ideal body weight. The average weight loss was 108 kg (range 53-155 kg).
Prior to surgery, the two heaviest subjects (patients 1 and 2 in Table 1) were symptomatic with daytime somnolence, loud snoring, and peripheral edema. Both of these men had hypercapnia and moderate hypoxemia on awake arterial blood gas analysis. The two remaining subjects (patients 4 and 5) were asymptomatic. At the time of restudy, all patients were asymptomatic. Repeat arterial blood gas analysis and pulmonary function tests in patients 1 and 2 were now within normal limits.
In all subjects, weight loss was accompanied by a reduction in the number of episodes per hour of sleep-disordered breathing. The mean number of episodes of sleep-disordered breathing per hour of sleep period time was 78 preoperatively and 1.4 after weight loss. In three of the four subjects, there was improvement in the severity of desaturation accompanying episodes of disordered breathing. This was most dramatic in the two previously symptomatic subjects whose lowest oxygen saturation during sleep was less than 50 percent prior to surgery, and 90 percent and 87 percent at restudy.
Analysis of the sleep characteristics of these subjects after weight loss (Table 2) showed a change in the direction toward deeper sleep with fewer awakenings. Sleep quality was, thus, improved.
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.
In a previous study, we demonstrated sleep-disordered breathing and nocturnal oxygen desaturation in a significant proportion of morbidly obese men scheduled for bypass surgery to control obesity. In that study, 14 morbidly obese subjects who were at least 200 percent of ideal body weight were monitored during a single night of sleep. Six of the seven men experienced oxygen desaturation or abnormal breathing. Two of these subjects were symptomatic with daytime somnolence.