Waist-to-hip ratio is associated with pulmonary gas exchange in the morbidly obese.
BACKGROUND
Morbidly obese individuals (ie, body mass index [BMI], > or = 40 kg/m2) may have a pulmonary gas exchange impairment due to the large fat mass surrounding their abdomen.


OBJECTIVE
To examine the effect of the waist-to-hip (W/H) ratio on pulmonary gas exchange in the morbidly obese.


METHODS
Twenty-five morbidly obese individuals (mean [+/- SD] age, 39 +/- 10 years; mean BMI, 49 +/- 7 kg/m2; mean body fat, 50 +/- 6%; mean waist circumference, 135 +/- 15 cm; mean W/H ratio, 0.97 +/- 0.11) scheduled for bariatric surgery were recruited. Arterial blood was sampled in duplicate after 5 min of rest sitting upright.


RESULTS
The mean PaO2 at rest was 88 +/- 7 mm Hg (range, 72 to 108 mm Hg), the alveolar-arterial oxygen pressure difference (P[A-a]O2) was 19 +/- 9 mm Hg (range, 1 to 37 mm Hg), and the PacO2 was 38 +/- 3 mm Hg (range, 32 to 44 mm Hg). Linear regression showed that 32% and 36%, respectively, of the variance in the P(A-a)O2 and PaO2 were explained by the W/H ratio (p < 0.004 for both). As well, 20% of the variance in PacO2 was explained by the W/H ratio (p = 0.02). Men had larger W/H ratios (p < 0.01) and poorer gas exchange (p = 0.06) compared to women (mean difference: PaO2, -7 mm Hg; P[A-a]O2, 6 mm Hg).


CONCLUSIONS
Morbidly obese men showed a trend to have poorer pulmonary gas exchange compared to morbidly obese women, and a significant part of the blood gas status in these patients is associated with the W/H ratio.
Zavorsky
Gerald S
GS
Department of Anesthesia, McGill University Health Center, Montreal General Hospital, 1650 Cedar Ave, Room D10-144, Montreal, QC, Canada H3G 1A4. gerald.zavorsky@mcgill.ca
Murias
Juan M
JM
Kim
Do Jun
DJ
Gow
Jennifer
J
Sylvestre
Jean-Loup
JL
Christou
Nicolas V
NV
D000328:Adult; D001784:Blood Gas Analysis; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000097:blood / Q000503:physiopathology*; D011187:Posture / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012146:Rest / Q000502:physiology; D012737:Sex Factors; D049629:Waist-Hip Ratio