Chest
Volume 92, Issue 4, October 1987, Pages 631-637
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Clinical Investigations
Changes in Breathing and the Pharynx after Weight Loss in Obstructive Sleep Apnea

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The effect of weight loss following dietary restriction on disordered breathing on the pharyngeal airway is controversial in patients with obstructive sleep apnea (OSA). We therefore prospectively studied eight patients before and after dietary-induced weight loss. Mean weight loss was 20.6 kg ± 12.8 SD. After weight loss there were significant improvements in Po2 and Pco2 measured during wakefulness, and in the number of desaturation episodes per hour of sleep, average desaturation per episode, and number of movement arousals. The number of apneas and hypopneas significantly decreased in six of eight patients. There was a significant correlation between body mass index and number of disordered breathing events. Nasopharyngeal collapsibility and pulse flow resistance decreased in awake patients after weight loss. We conclude that moderate weight loss in obese patients with OSA improves oxygenation during both sleep and wakefulness, decreases the number of disordered breathing events in many patients, and decreases the collapsibility of the nasopharyngeal airway.

Section snippets

Patients

Between November, 1982 and June, 1985, 12 patients with OSA entered the weight reduction program described below. Four of the 12 patients were excluded from this study, three because they had significant concomitant obstructive lung disease (FEV1/FVC <65 percent) and required changes in their doses of bronchodilator and corticosteroid medications. One patient was excluded because he was schizophrenic and unable to cooperate with the testing.

Of the eight obese patients with OSA studied, there

RESULTS

All patients had obstructive apnea characterized by absent airflow despite swings in esophageal pressure. Mean weight loss in all patients was 20.6 kg ± 12.8 SD (Table 1).

After weight loss there was a significant improvement in Po2 and Pco2 measured during wakefulness (p<0.05), but no significant change in pH (Table 2).

During sleep there was a statistically significant improvement in the number of desaturations per hour of sleep, the average desaturation/episode and the median saturation

DISCUSSION

This study has shown that weight loss averaging 21 kg following caloric restriction significantly improved oxygenation during sleep and during wakefulness. It also demonstrated that the number of apneas and hypopneas per hour of sleep significantly improved in six of eight patients. Weight loss also decreased the number of movement arousals per hour of sleep. In addition, weight loss also decreased the collapsibility of the nasopharyngeal airway in awake patients.

We observed that nasopharyngeal

ACKNOWLEDGMENTS

We wish to acknowledge the meticulous technical assistance of Ms. Kathy Irwin in performance of sleep studies, and of Ms. Anne Suratt in the analysis of the data. We acknowledge the cheerful and patient help of Mrs. Martha Waring in the recruitment and encouragement of patients and in the preparation of the manuscript. We also wish to acknowledge the assistance of the staff of the Diabetes/Nutrition Unit at The Blue Ridge Hospital Division of the University of Virginia.

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    Supported by grants HL 30218 and RR 00847 from The National Institutes of Health.

    Manuscript received December 8; revision accepted March 4.

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