R. O. Crapo

We performed spirometry on 114 morbidly obese patients considered for gastric bypass surgery to assess its efficacy as a preoperative screening test. One hundred eight subjects underwent surgery, and 61 patients returned for repeat spirometry 1 year later. The average preoperative forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and mid flow (FEF25-75%) were 100% of predicted. Spirometry identified no more of our obese subjects as abnormal than would have been identified in a group of healthy, nonobese individuals. Each surgical case was reviewed. An abnormal preoperative spirogram did not identify the patients who experienced postoperative complications. Weight loss was associated with very small increases in FVC (300 ml) and FEV1 (245 ml). Preoperative spirometric testing is not indicated in morbidly obese patients with no other identifiable risk factors for postoperative respiratory complications.

To examine the mechanism of exercise limitation associated with chest wall restriction (CWR), we compared the ramp (1 W/3 s) exercise performance of six untrained subjects with ankylosing spondylitis (AS) and six healthy subjects matched for age and body size. Subjects with AS had CWR (maximum rib cage expansion : 1.4 +/- 0.2 cm; means +/- sem). The maximum oxygen uptake (VO2max) of AS subjects (2.15 +/- 0.2 1-stpd) was less than their predicted VO2max (2.68 +/- 0.13 1-stpd; p less than 0.03) and the measured VO2max of matched healthy subjects (2.78 +/- 0.22 1-stpd; p less than 0.03). Subjects with AS achieved 95 percent of predicted maximum heart rate, and their maximum voluntary ventilation exceeded their maximum exercise ventilation by at least 15 l X min-1 unless parenchymal pulmonary disease was present. We conclude that maximum ramp exercise performance of AS subjects with CWR is decreased. Deconditioning or cardiovascular impairment rather than ventilatory impairment appears responsible for the observed reduction of VO2max.