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.
Zavorsky
G S
GS
Department of Obstetrics, Gynecology and Women's Health, School of Medicine, Saint Louis University, Saint Mary's Health Center, Saint Louis, Missouri 63117, USA. zavorsky@slu.edu
Hoffman
S L
SL
D001784:Blood Gas Analysis; D015992:Body Mass Index; D002245:Carbon Dioxide / Q000032:analysis / Q000097:blood; D015444:Exercise / Q000502:physiology*; D006801:Humans; D009767:Obesity, Morbid / Q000097:blood / Q000503:physiopathology*; D010100:Oxygen / Q000032:analysis / Q000097:blood; D010313:Partial Pressure; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D015431:Weight Loss / Q000502:physiology*
D002245:Carbon Dioxide; D010100:Oxygen