Chest
Volume 90, Issue 1, July 1986, Pages 81-86
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Gastric Surgery for Respiratory Insufficiency of Obesity

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Morbid obesity is often associated with severe respiratory insufficiency, commonly known as the pickwickian syndrome. This can be divided into the following two primary breathing disorders which can affect patients alone or in combination: (1) the obstructive sleep apnea syndrome (SAS); and (2) the obesity-hypoventilation syndrome (OHS). Thirty-eight (14 percent) of 263 morbidly obese patients with respiratory insufficiency of obesity underwent gastric surgery for weight reduction. Ten had OHS, nine has SAS, and 19 had both. Of these patients, one died of postoperative complications, one died at five weeks with an inconclusive autopsy, one was lost to follow-up, and the time since surgery was too short (less than three months) in three. A total of 30 patients lost 45±25 percent (p<0.0001) of excess body weight within 3 to 12 months following surgery, when repeat pulmonary studies were done. Most patients continued to lose additional weight until two years, when they had lost 62±26 percent of excess weight. Nine patients failed initial surgery (gastroplasty); seven of these were successfully converted to gastric bypass. Weight loss was associated with a significant decrease in the percentage of sleep apnea from 44±15 to 8±11 (p<0.0001). In patients with OHS, the arterial oxygen pressure (PaO2) increased from 53±9 to 68±11 mm Hg (p<0.0001), and the arterial carbon dioxide tension decreased from 51±7 to 41±4 mm Hg (p<0.0001). Pulmonary function tests in the patients with OHS revealed significant increases, as a percentage of predicted normal, in the forced vital capacity, forced expiratory volume in one second, expiratory reserve volume, functional residual capacity, and total lung capacity. Secondary polycythemia, defined as a hemoglobin level greater than 16 g/dl associated with a PaO2 less than 60 mm Hg, was noted in 13 of 29 patients with OHS. This fell from 16.9±1.1 to 14.9±1.7 g/dl (p<0.001) after weight loss and improved pulmonary function.

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MATERIALS AND METHODS

Patients were considered for surgical treatment of obesity if (1) they weighed 45 kg (100 lbs) or more above ideal weight calculated from the 1959 height-weight tables of the Metropolitan Life Insurance Co.15 and (2) had failed to lose or maintain weight loss by supervised dietary manipulation for five years or more. Obese patients with respiratory failure were accepted without documentation of failed dietary management. Respiratory insufficiency of obesity comprised three groups of patients

Patient Population

Between March 1979 and February 1985, some 263 patients underwent surgery for morbid obesity. Of these, 161 patients had gastroplasty, and 102 had Rouxen-Y gastric bypass. Thirty-eight (14 percent) were identified with respiratory insufficiency of obesity; 25 of these had a gastroplasty and 13 a gastric bypass as their primary operation for obesity. Nine had SAS, ten had OHS, and 19 had both (Table 1). An associated pulmonary problem was present in 20 of these 38 patients, including heavy

DISCUSSION

The effects of morbid obesity on the respiratory system can be equated to placing a heavy weight on the chest wall. The ERV23 and total compliance of the respiratory system24 are decreased. Increased body mass necessitates an increased consumption of oxygen and production of carbon dioxide.25 Mild hypoxemia is common, but increased alveolar ventilation maintains PaCO2 within the normal range. Superimposed on these pulmonary abnormalities, characteristic of many individuals with simple obesity,

ACKNOWLEDGMENTS

We thank the medical and surgical house officers, nurse anesthetists, anesthesiologists, pulmonary function technicians, respiratory therapists, and nursing staff of the Medical College of Virginia for their outstanding efforts in the management of these very challenging patients.

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Manuscript received August 26; revision accepted December 11.

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