Seventeen eucapnic massively obese patients and eight normal subjects had their respiratory cycle parameters studied while breathing room air at rest. Despite large variations in the degree of obesity, our patients demonstrated normal mean inspiratory and expiratory flow rates, duty cycles, and minute ventilation. The maintenance of normal mean inspiratory flow rates was found to be dependent on an augmentation of neuromuscular drive (P0.1); furthermore, a strong positive correlation between percentage ideal body weight (i.e., the degree of obesity) and P0.1 was present. The obese were found to partition their tidal volume preferentially to their rib cage compartment, choosing to leave the abdominal compartment relatively immobile. Analysis of the diaphragmatic electromyogram revealed a persistence of activity into early expiration, the length of which also depended on the degree of obesity. These findings suggest that the diaphragm's volume-generating function in the obese is reduced, and furthermore the persistence of its activity in expiration serves to attenuate the rate of expiratory flow. No significant difference in any respiratory cycle parameter was found between simple obesity patients and formerly hypercapnic obese patients.

We studied the action of the costal and crural (vertebral) parts of the diaphragm on the lower rib cage in normal supine dogs. The two parts of the diaphragm were separately stimulated by electrodes directly implanted in the muscle or via the different phrenic nerve roots in the neck. The results of the experiments indicate the following. 1) The costal and crural parts of the diaphragm have a different segmental innervation and a different mechanical action on the rib cage. 2) The costal diaphragm expands the lower rib cage when it contracts. This rib-cage expansion is due mostly to the fulcrum of the abdominal contents and partly to the rise in abdominal pressure that takes place during diaphragmatic contraction. The pericardial attachments play no role in this action of the diaphragm. 3) The action of the crural diaphragm on the lower rib cage depends only on the balance between the inspiratory force exerted by the rise in abdominal pressure and the expiratory force exerted by the fall in pleural pressure. In the intact animal at functional residual capacity, these two opposite effects cancel each other. 4) The inflationary action of both parts on the rib cage decreases progressively as lung volume increases. The findings also suggest that the rise in abdominal pressure which occurs when the diaphragm contracts expands the lower rib cage by acting through the area of apposition of the diaphragm to the rib cage. These findings also strengthen the idea that the diaphragm actually consists of two muscles.

In an attempt to explain the clinical efficacy of aminophylline, we studied its effect on diaphragmatic function in eight normal subjects. The relation between the electrical activity of the diaphragm and the pressure generated by the diaphragm was assessed during voluntary contractions before and after aminophylline infusion. Aminophylline shifted the electrical activity/pressure curve to the left; the pressure at a given electrical activity increased an average of 15 per cent (P less than 0.001). In four subjects, pressure was also measured during stimulation of the phrenic nerve at various frequencies before and after diaphragmatic fatigue was produced by resistive breathing, with and without aminophylline infusion. Pressure increased after fatigue at all stimulation frequencies with aminophylline, as compared with the pressure after identical fatigue runs at the same stimulation frequencies without aminophylline. The mean plasma aminophylline concentration associated with these responses was 13 +/- 0.9 mg per liter. We conclude that aminophylline improves the diaphragm's contractility and renders it less susceptible to fatigue.

A weed survey of 115 Nova Scotia lowbush blueberry fields was conducted during the summers of 1984 and 1985 to determine the most common and prevalent weeds associated with blueberry production. A total of 119 weed species were observed within the surveyed blueberry fields. The most common weed species were bunchberry, colonial bentgrass, poverty oatgrass, sheep sorrel, and false lily-of-the-valley. Weeds with low relative abundance in this study, but which may become more widespread, include three-toothed cinquefoil, Kentucky bluegrass, hair fescue, canker-root, and Canadian St. Johnswort.

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The costal and crural parts of the diaphragm were separately stimulated in anesthetized dogs. Stimulation of the costal part increased the dimensions of the lower rib cage, whereas stimulation of the costal part decreased the dimensions of the lower rib cage. It is concluded that the diaphragm consists of two muscles that act differently on the rib cage.

A patient with obstructive sleep apnea was monitored five times during three years while his weight fluctuated within a range of 26 kg. The number of apneas per hour of sleep varied from 59.6 at 111 kg of weight to 3.1 at 85 kg. The relation between apneas per hour of sleep and body weight was a logarithmic function. A modest decrease in weight was thus associated with a disproportionally larger decrease in the rate of apneas. Typical SaO 2 levels during the apneic episodes also had a logarithmic relation with body weight. Apnea-related sinus bradycardia and sinus tachycardia were only present at the highest weight. The results suggested that dieting and weight loss lead to an improvement in sleep apnea and related sequelae.Obstructive sleep apnea syndrome is characterized by a repetitive and periodic occlusion of the upper airway during sleep. The mechanisms involved in this disorder are not well understood at present. 1 Obesity is seen in the majority of patients with sleep apnea. Redundant tissue in the oropharyngeal airway associated with obesity is thought to be a contributing factor. Surgical intervention by tracheostomy or uvulo-palato-pharyngoplasty is the treatment of choice, especially in the presence of apneic-induced cardiac arrhythmias, but case reports have suggested improvement in the obstructive sleep apnea and related sequelae following weight loss. 2-4 The exact relation between this syndrome and body weight remains ambiguous, however, as previous reports are based on single observations following weight reduction. We have monitored the sleep of a patient with obstructive sleep apnea five times during the course of nearly three years while his weight fluctuated from 85 kg to 111 kg. A logarithmic relation between the rate of apneas during sleep and body weight is demonstrated by this patient. Case ReportA 52-year-old white man was referred for evaluation of uncontrolled daytime sleepiness. The patient reported a 19-year history of hypersomnia and falling asleep at inappropriate times. Symptoms were reported as relatively stable over the past ten years. The patient noted loud snoring and excessive sweating during sleep. Although he denied cataplexy, hypnagogic hallucinations and sleep paralysis, narcolepsy was diagnosed two years prior to our evaluation based solely on the reported hypersomnia.Physical examination revealed an obese man (173 cm tall, weighing 111 kg), extremely drowsy, but otherwise in no distress. Pertinent medical disorders included essential systemic

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