ROLE OF CARDIOPULMONARY EXERCISE TESTING AND THE CRITERIA USED TO DETERMINE DISABILITY IN PATIENTS WITH SEVERE CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

The aim of this study was to evaluate the precision and variability with which resting pulmonary function tests (resting PFTs) can be used to predict the capacity in exercise, and the usefulness of the different measurements of pulmonary function in the evaluation of impairment/disability in patients with chronic obstructive pulmonary disease (COPD). We studied 78 patients with stabilized COPD (FEV, 45.1 +/- 17.1%). Of these, 39 suffered severe impairment according to the resting PFTs. Both the group with severe impairment (maximal oxygen consumption [VO2,max]: 16.22 +/- 5 ml/kg/min; maximal minute ventilation [VEmax]: 31.87 +/- 7.1 L/min; maximal heart rate [HRmax]: 133.8 +/- 10.9 beats/min) and the group with nonsevere impairment according to the resting PFTs (VO(2)max: 22.55 +/- 7.9 ml/kg/min; VEmax: 42.11 +/- 10.9 L/min; HRmax: 138 +/- 13.7 beats/min) showed ventilatory limitation during exercise. FEV(1) was the most prevalent criterion for the determination of severe impairment (FEV(1) < 40%), and was the variable best correlated to VO(2)max (r = 0.52 with VO(2)max as absolute value and r = 0.54 with VO(2)max expressed as a percentage of the reference value), but the resting PFTs were not predictive of exercise performance including patients with severe COPD. Evaluation of working capacity (based on VO(2)max) revealed a significant number of inaccurate predictions among the results of the resting PFTs. Sensitivity and specificity analysis were used to compare the different criteria used to evaluate the severity of disability. They reveal that the classification will be different according to the criteria used. The criteria that classified more patients similarly were VO(2)max < 60% of the reference values (sensitivity of 64.1% and specificity of 66.6%) and VO(2)max < 15 ml/kg/min (sensitivity of 41% and specificity of 79.5%). The impairment rating whenever the theoretical energy requirements of the job exceeded 40% of the patients' VO(2)max (handicap) was contradicted by other exercise criteria. A combination of exercise testing results and job energy requirement may be necessary for an accurate determination of impairment/disability for the individual subject.