PREDICTION OF MAXIMAL EXERCISE CAPACITY IN OBSTRUCTIVE AND RESTRICTIVE PULMONARY-DISEASE

We evaluated the predictive value of resting pulmonary function tests (PFTs) in the determination of maximal exercise capacity in patients w ith obstructive and restrictive ventilatory disease. We performed rest ing PFTs and an incremental exercise study on a bicycle ergometer in 1 46 patients with chronic obstructive pulmonary disease (COPD) and 68 p atients with restrictive disease. The patients with obstructive diseas e were further subdivided into mild, moderate, and severe based on the severity of their airway obstruction (mean +/- SD:FEV1, 2.78 +/- 0.77 , 2.12 +/- 0.74, and 1.06 +/- 0.47, respectively). Correlation coeffic ients for PFTs vs VO2max and VEmax in restricted patients was generall y low (DL = 0.67 and 0.34, IC = 0.58 and 0.35, FVC = 0.57 and 0.35, TL C = 0.35 and 0.18). In patients with COPD, the maximum voluntary venti lation (MVV) was the single best predictor of VO2 in all groups with c orrelation coefficients of 0.75, 0.69, and 0.89 in the mild, moderate, and severe subgroups, respectively. Similarly, the MW was the best pr edictor Of VEMax in all groups with correlation coefficients of 0.59, 0.64, and 0.89 in the three subgroups. The correlation with FEV1 was s lightly less for both VO2max (0.69, 0.65, and 0.87) and V EMax (0.52, 0.64, 0.64) in the mild, moderate, and severe subgroups, respectively. Our findings show that PFTs are unreliable in predicting VEmax and VO 2max in restricted patients. In patients with obstruction, the MVV is the single best predictor of VO2max and VEmax in all three categories, but was not significantly improved by stepwise multiple regression wi th additional PFT variables. Higher correlations were obtained in the severe group in whom the correlation with VO2max and VEmax was 0.89. H owever, the 95 percent confidence interval of the estimate for VO2 and VE was relatively large (+/- 0.16 L/min and +/- 6.6 L/min, respective ly). We conclude that although several PFTs correlate significantly wi th maximum exercise, the large variance precludes their use to accurat ely predict maximum performance in individual patients with COPD.