Snoring, daytime sleepiness, and sickle cell anemia.
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The pathophysiologic events that lead to the loss of airway compensation in obstructive sleep apnea (OSA) are poorly understood. The development of airway instability may be secondary to changes in neurologic control, airway morphology, or both. To identify potential histopathologic features of pharyngeal tissues that may contribute to OSA, transverse sections of the distal soft palate and uvula were qualitatively compared using light and electron microscopy from 4 severe apneics (greater than 50 apnea/hour), 4 severe snorers (less than 20 apnea/hour), and 4 nonsnorers. Light microscopy of both apneics and snorers revealed mucous gland hypertrophy with ductal dilation and focal squamous metaplasia, disruption of muscle bundles by infiltrating mucous glands, focal atrophy of muscle fibers, and extensive edema of the lamina propria with vascular dilation. Severe snorers did not differ qualitatively from apneics in the characteristic changes found; however, some snorers had less extensive changes. No distinctive histopathologic findings could be associated with the development of apnea. Electron microscopy of severe apneics identified frequent focal degeneration of myelinated nerve fibers and axons. The finding of similar histopathologic changes in apneics and severe snorers supports previous speculation of a common etiology not directly related to apnea, such as vibratory trauma to pharyngeal tissues. Degenerative changes in peripheral nerves, identified on electron microscopy, however, may contribute to airway instability and the development of obstructive apnea by impairing pharyngeal reflexes.
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The diagnostic value of flow-volume curves for sleep apnea was studied in 32 patients with obstructive sleep apnea, 40 simple snorers, and 30 healthy nonsnorers. A sawtooth appearance of the flow-volume curve was seen in 22 of the sleep apnea patients (69%), 14 of the simple snorers (35%), and 10 of the nonsnorers (33%). The ratio of midexpiratory flow (FEF 50) to midinspiratory flow (FIF 50) was greater than 1 in 6 of the sleep apnea patients (19%), 3 of the simple snorers (8%), and 2 of the nonsnorers (7%). Thus, only the sawtooth sign was more frequently found in sleep apnea patients than in controls (p less than 0.01). Sleep apnea patients with a sawtooth appearance of the flow-volume curve had a higher apnea index (38.7 +/- 22 vs. 21.5 +/- 12.1; p less than 0.01) and lower nocturnal minimum oxygen saturation (68.1% +/- 16.8 vs. 81.3% +/- 9.97; p less than 0.01) than those without. In symptomatic snorers, sensitivity of the sawtooth sign for sleep apnea was 72% and specificity 61%, for a FEF50/FIF50 ratio above 1 sensitivity was 17% and specificity 83%. In asymptomatic patients, sensitivity of either sign was extremely poor (33%) and specificity was 67% for the sawtooth sign and 85% for FEF50/FIF50 greater than 1. We conclude that abnormal flow-volume curves are of limited value for predicting sleep apnea.
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Published in Sudhoffs Archiv für Geschichte der Medizin und Naturwissenschaften, 1941.
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Severe obstructive sleep apnea, a disturbance of sleep resulting from intermittent periodic obstruction of the upper airway, was diagnosed after cardiotocography during which the external tocodynamometer disclosed a pattern initially thought to represent uterine activity. In spite of this obstructive sleep apnea with associated markedly low, hypoxic oxygen saturation levels and daytime somnolence of 10 to 12 hours from 32 weeks until delivery, subsequent fetal outcome was good.
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