Pulmonary function in obese patients scheduled for jejuno-ileostomy

Pulmonary gas exchange in the morbidly obese

The literature on pulmonary gas exchange at rest, during exercise, and with weight loss in the morbidly obese (body mass index or BMI > or = 40 kg m(-2)) is reviewed. Forty-one studies were found (768 subjects weighted mean = 40 years old, BMI = 48 kg m(-2)). The alveolar-to-arterial oxygen partial pressure difference (AaDO2) was large at rest in upright subjects at sea level (23, range 5-38 mmHg) while the arterial pressure of oxygen (PaO2) was low (81, range 50-95 mmHg). Arterial pressure of carbon dioxide (PaCO2) was normal. At peak exercise (162 W), gas exchange improves. Weight loss of 45 kg (BMI = -13 kg m(-2)) over 18 months is associated with an improvement in PaO2 (by 10 mmHg, range 1-23 mmHg), a reduction in AaDO2 (by 8 mmHg, range -3 to -16 mmHg), and PaCO2 (by -3 mmHg, range 3 to -14 mmHg) at rest. Every 5-6 kg reduction in weight increases PaO2 by 1 and reduces AaDO2 by 1 mmHg, respectively. Morbidly obese women have better gas exchange at rest compared with morbidly obese men which is likely due to lower waist-to-hip ratios in women than from differences in weight or BMI.

Anaesthesia in the morbidly obese. A comparison of anaesthetic and analgesic regimens for upper abdominal surgery

Seventy morbidly obese patients presented for upper abdominal surgery; 17% had pre-existing cardiovascular disease and 23% pre-existing respiratory disease. Twenty-eight patients received general anaesthesia, plus narcotic analgesia postoperatively, and 42 general anaesthesia plus thoracic epidural analgesia intra- and postoperatively. Aspects of anaesthetic management are discussed and compared with previous similar reports. Doses of local anaesthetic for induction of epidural analgesia were less than those for the non-obese but doses of local anaesthetic for maintenance of epidural analgesia were similar to those in non-obese patients. Patients who had thoracic epidural analgesia required less volatile anaesthesia than the group who had general anaesthesia and narcotic analgesics. Postoperative respiratory complications were more common in patients with pre-existing cardiovascular and respiratory disease, and occurred less frequently in patients who had thoracic epidural analgesia.

Sleep-disordered breathing and oxygen desaturation in obese patients

Fourteen morbidly obese subjects, referred to our institution for bypass surgery for obesity, were studied with regard to pulmonary function and respiratory patterns during sleep. The seven female patients experienced no episodes of desaturation or disordered breathing during sleep. Six of the seven male patients experienced desaturation or disordered breathing. The one who did not had hypogonadism, suggesting that testosterone may have a role in the regulation of breathing during sleep. The two patients with the most frequent episodes of apnea and lowest oxygen saturation had a clinical picture consistent with the pickwickian syndrome. This supports the relationship previously noted between the degree of hypoxia and the presence of hypersomnolence.