Compensatory exercise hyperventilation is restored in the morbidly obese after bariatric surgery.
BACKGROUND
Morbidly obese individuals may have poor compensatory hyperventilation during exercise. The objective was to examine pulmonary gas exchange and the compensatory hyperventilatory response during exercise pre- and post-weight reduction surgery in obese subjects.


METHODS
Fifteen patients (age=39+/-8 years, body mass index=47+/-6 kg/m2), with an excess weight of 69+/-17 kg, were recruited. Pulmonary function at rest was assessed and arterial-blood gases were sampled at rest and all levels of exercise pre- and 10+/-3 weeks postsurgery.


RESULTS
There was a loss of excess weight 21+/-6 kg (p<0.01). Waist and hip circumference decreased by 13+/-9 and 8+/-7 cm, respectively (p<0.01). Prior to surgery, there was no compensatory hyperventilation between rest and peak exercise as arterial PCO2 (PaCO2) remained unchanged (37+/-3 mm Hg). However, postsurgery, there was compensatory hyperventilation as PaCO2 decreased to 33+/-2 mm Hg at peak exercise (p<0.01), with no change in peak oxygen consumption (VO2peak in L/min). Multiple linear regression revealed that the restored ventilatory response to exercise was most strongly associated with the reduction in overall fat mass (adjusted r2=0.25; p=0.03). Total weight loss of 21 kg induces adequate compensatory hyperventilation that begins to show at about 50% of VO2peak, resulting in improved gas exchange at moderate to peak exercise intensities.


CONCLUSIONS
Improvement in compensatory hyperventilation is most closely related to loss in overall fat mass.
Zavorsky
Gerald S
GS
Department of Obstetrics, Gynecology and Women's Health, School of Medicine, Saint Mary's Health Center, Saint Louis University, 6420 Clayton Road, Room 290, Saint Louis, MO 63117, USA. zavorsky@slu.edu
Kim
Do Jun
DJ
Christou
Nicolas V
NV
D000328:Adult; D001823:Body Composition; D015897:Comorbidity; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006985:Hyperventilation; D008875:Middle Aged; D009767:Obesity, Morbid / Q000453:epidemiology / Q000503:physiopathology* / Q000601:surgery; D010101:Oxygen Consumption; D010108:Oxyhemoglobins / Q000378:metabolism; D011184:Postoperative Period; D011659:Pulmonary Gas Exchange; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology; D013147:Spirometry
D010108:Oxyhemoglobins