INFLUENCE OF EXCESSIVE WEIGHT-LOSS AFTER GASTROPLASTY FOR MORBID-OBESITY ON RESPIRATORY MUSCLE PERFORMANCE

Background - Morbidly obese. subjects are known to have impaired respi ratory function and inefficient respiratory muscles. A study was under taken to investigate the influence of excessive weight loss on pulmona ry and respiratory muscle function in morbidly obese individuals who u nderwent gastroplasty to induce weight loss. Methods - Twenty one obes e individuals with mean (SE) body mass index (BMI) 41.5 (4.5) kg/m(2) without overt obstructive airways disease (FEV1/FVC ratio >80%) were s tudied before and six months after vertical banded gastroplasty. Only patients who had lost at least 20% of baseline BMI were included in th e study. Standard pulmonary function tests and respiratory muscle stre ngth and endurance were measured. Results - Before operation the predo minant abnormalities in respiratory function were significant reductio ns in lung volumes and respiratory muscle endurance and, to a lesser d egree, reductions in respiratory muscle strength. All parameters incre ased towards normal values after weight loss with significant increase s in functional residual capacity (FRC) from 84.0 (2.2) to 91.3 (2.5)% of predicted normal values (mean difference 7.3, 95% confidence inter val of difference (CI) 4.2 to 10.5), total lung capacity (TLC) from 85 .6 (3.0) to 93.5 (3.7)% of predicted normal values (mean difference 7. 9, 95%, CI 4.5 to 11.5), residual volume (RV) from 86.7 (3.1) to 96.4 (3.0)% of predicted normal values (mean difference 9.7, 95% CI 5.2 to 14.1), expiratory reserve volume (ERV) from 76.6 (3.0) to 89.0 (3.4)% of predicted normal values (mean difference 12.4, 95% CI 6.3 to 18.9), respiratory muscle strength: PImax from 92 (4.4) to 113 (4.6) cm H2O (mean difference 21, 95% CI 12.2 to 31.6), PEmax from 144 (5.6) to 166 (4.3) cm H2O (mean difference 22, 95% CI 12.9 to 32.0), and endurance : PmPeak/PImax from 56 (1.4) to 69 (2.0)% (mean difference 13, 95% CI 9.7 to 16.9). The strongest correlation was between weight loss;md the improvement in respiratory muscle endurance. Conclusions - Lung volum es and respiratory muscle performance are decreased in obese individua ls. Weight loss following gastroplasty is associated with improvement in lung volumes and respiratory muscle function.