OBES SURG (2008) 18:549–559 DOI 10.1007/s11695-008-9437-7
RESEARCH ARTICLE
Compensatory Exercise Hyperventilation is Restored in the Morbidly Obese After Bariatric Surgery Gerald S. Zavorsky & Do Jun Kim & Nicolas V. Christou
Received: 31 August 2007 / Accepted: 11 September 2007 / Published online: 18 March 2008 # Springer Science + Business Media, LLC 2008
Abstract 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 G.S. Zavorsky is the recipient of the 2005 Baxter Corporation Award in Anesthesia from the Canadian Anesthesiologist’s Society. G.S. Zavorsky is also Research Scholar–Junior 1 from the Quebec Health Research Foundation (Fonds de la Recherche en Santé du Québec). N.V. Christou is a consultant for Ethicon Endo-Surgery and has stock ownership in Weight Loss Surgery. G. S. Zavorsky (*) : D. J. Kim 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 e-mail:
[email protected] G. S. Zavorsky Department of Pharmacological and Physiological Science, School of Medicine, Saint Louis University, 402 South Grand Blvd., Saint Louis, MO 63104, USA N. V. Christou Department of Surgery, Bariatric Clinic, McGill University Health Center, Royal Victoria Hospital, 687 Pine Ave. West., Rm S9.030, Montreal, Quebec H3A-1A1, Canada
8±7 cm, respectively ( p38.0 mm Hg suggests an absence of a compensatory hyperventilatory response during intense exercise [13]. The limited data have shown that in the morbidly obese, mean PaCO2 is ≥35 mm Hg at peak exercise, suggesting insufficient compensatory hyperventilation [8–11]. Temperature-correcting those data would increase PaCO2 even more [12], further supporting insufficient hyperventilation during exercise in these subjects. Because obesity results in increased ventilatory constraints due to the large abdominal fat mass surrounding the chest [14, 15] that can promote ventilation-perfusion inequality (low V/Q ratios) [16], it would be interesting to examine how rapid weight and abdominal fat loss can improve compensatory hyperventilation during exercise. There are no data on how weight reduction surgery (bariatric surgery) in the morbidly obese affects pulmonary gas exchange and compensatory hyperventilation during exercise. Consequently, the purpose of this study was to determine the effects of rapid weight loss from bariatric surgery on pulmonary gas exchange in the morbidly obese. The hypothesis was that there would be no compensatory hyperventilatory response to exercise prior to surgery, and that compensatory hyperventilation would be restored and pulmonary gas exchange would be improved at various exercise intensities postsurgery. The novelty of this study is that temperature-corrected arterial blood-gases are sampled at rest and at the same levels of oxygen consumption (L/min) pre- and 10 weeks post-surgery. Thus, it could be determined at which submaximal exercise intensity a reduction in PaCO2 would be found compared to presurgery. Furthermore, we used a stepwise multiple linear regression to mechanistically examine which factors (the decrease in waist or hip circumference, waist-to-hip ratio, BMI, fat free mass or fat mass, or a combination of these factors) is most strongly associated with improvements in compensatory hyperventilation.
OBES SURG (2008) 18:549–559
Methods Subjects Twenty-four morbidly obese subjects (body mass index or BMI>40 kg/m2) were recruited from the bariatric clinic. Each subject was required to participate in two testing sessions, one pre- and one postsurgery testing session (about 2 months postsurgery). The tests included body composition, pulmonary function at rest, and, arterial blood sampling at rest and during a graded cycling exercise test to volitional exhaustion (V_ O2peak test). Excluded from the population of the morbidly obese were individuals with (1) BMI ≥70 kg/m2; (2) respiratory, renal, or hepatic failure; (3) metastatic disease; (4) senility, Alzheimer’s disease, or other dementias; and (5) in-ability to comprehend the instructions during tests. All subjects signed an informed consent form. This study was approved by the Institutional Review Board of the McGill University Health Centre. Body Composition and Venous Blood Samples Height, weight, lung function, and body composition were assessed pre- and postsurgery. Lean and fat mass were measured from an eight-polar bioelectrical impedance device that has been validated for the morbidly obese [17]. The excess weight was estimated according to a formula [18] and is based on the ideal weight for medium framed individuals according to the Metropolitan Life Insurance Company Tables (1983). The percent excess weight loss was calculated as 100×[(W0 −W1)/EW0], where W0 is the weight in kilograms at the time of surgery, W1 is the weight in kilograms at the last follow-up, and EW0 is the excess weight at the time of surgery. Venous blood was withdrawn from an anticubital vein for the measurement of progesterone as to control for the menstrual cycle phase in women and lipid/diabetic profiles for determination of metabolic syndrome. Arterial Catheterization Arterial cannulation of the radial artery was performed 15 min prior to the graded exercise test under local anesthesia (2% lidocaine) using the procedure and the same blood-gas analyzer with multiwavelength oximetry described elsewhere [12]. A teflon-coated thermocouple was positioned in the hub of the radial artery catheter to measure arterial blood temperature. The highest recorded temperature seen from the thermocouple during withdrawal was recorded as the arterial blood temperature. Arterial blood gases were measured after 5 min of rest, with the subjects in an upright and seated position. The average of duplicate
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Table 1 Changes in anthropometric parameters with weight loss n=15 (women=11; men=4)
Anthropometric parameters Age (years) Height (cm) Weight (kg) Excess weight (kg) Percent excess weight loss Body mass index (kg/m2) Body surface area (m2) Waist circumference (cm) Hip circumference (cm) Waist-to-hip ratio Fat-free mass (kg) Fat mass (kg) Body fat (%)
Presurgery Mean (SD)
10 weeks postsurgery Mean (SD)
Change Mean (SD)
95% confidence interval for the change
39 (8) 167 (8) 131.9 (20.1) 69.1 (17.7) – 47.3 (6.2) 2.4 (0.2) 128.3 (13.4) 136.4 (11.6) 0.95 (0.12) 66.5 (13.7) 65.4 (12.9) 49.7 (6.2)
– – 111.2 (17.2) 48.4 (16.0) – 40.0 (6.0) 2.2 (0.2) 114.9 (11.3) 128.2 (13.2) 0.90 (0.10) 59.7 (12.8) 51.4 (13.7) 46.1 (8.7)
– – −20.7 (6.3)** −20.7 (6.3)** 31 (8)** −7.4 (1.8)** −0.2 (0.1)** −13.4 (9.1)** −8.2 (7.2)** −0.04 (0.08)* −6.7 (1.7)** −14.0 (5.6)** −3.6 (3.1)**
– – −23.9, −17.5 −23.9, −17.5 – −8.3, −6.5 −0.3, −0.1 −18.0, −8.8 −11.8, −4.6 −0.08, 0 −7.6, −5.8 −16.8, −11.2 −5.2, −2.0
The change between pre- and postsurgery is significant. Body surface area was calculated as 0.0097 (height in cm+weight in kg)−0.545 *p
