Chronic obstructive pulmonary disease patients and healthy subjects : a comparison of ventilatory patterns used during maximal exercise and predicting maximal oxygen uptake from resting pulmonary function testing.

The purposes of this study were to develop equations to predict maximal oxygen uptake from resting measures of pulmonary function testing (PFT) and to compare the ventilatory patterns used during maximal exercise in chronic obstructive pulmonary disease (COPD) patients and healthy non-smoking subjects. Eleven COPD patients (8 males and 3 females) and 8 healthy male subjects were given PFT and a graded, maximal treadmill test. As expected, the healthy subjects performed significantly better on the PFT and treadmill test. Several resting PFT measures were significantly correlated with maximal oxygen uptake expressed as ml∙kg^-1∙min^-1 and liters/min. Regression equations were:

ml∙kg^-1∙min^-1= 5.326 + 12.17 X maximum ventilatory volume/mass (kg), r = 0.90, S.E.E. = 4.4 ml∙kg^-1∙min^-1

m ml∙kg^-1∙min^-1 = 6.19 + 2.259 X peak expiratory flow (percentage of expected), r = 0.79, S.Ε.Ε. = 6.4 ml∙kg^-1∙min^-1

liters/ min = 0.0326 + 0.2437 X peak expiratory flow (PEF), r=0.89, S.E.E. = 0.413 liters/min.

liters/min 0.0041 0.8166 X carbon monoxide diffusing capacity (D_Lco), r = 0.83, S.E.E. = 0.507 liters/min

liters/min -0.2282 + 0.167 X PEF + 0.038 X D_Lco 0.93, S.Ε.Ε. 0.34 liters/min

Four variables were used to characterize ventilatory patterns during maximal exercise, tidal volume/forced vital capacity (V_t/FVC), maximal ventilation/MVV (Ve_max/MVV), frequency of breathing (F_b) and peak expired flow at rest/peak expired flow during exercise (F_Prest/F_Pex). The COPD patients' mean Ve_max/MVV ratio (74 ± 25%) was significantly higher than the healthy subjects, (62 ± 22%, p < 0.03 ) The healthy subjects had a greater V_t/FVC ratio (62 ± 11%) than the COPD patients (47 ± 13%, p < 0.01 ) . The F_b did not differ between groups; 31.7 ± 7.8 breaths per minute for the COPD patients and 32.0 ± 4.1 breaths per minute for the healthy subjects. F_Prest/F_Pex did not differ between groups, 68 ± 30% for the COPD patients and 62 ± 22% for the healthy subjects.