The relationship between work done and pulmonary function; validation of a method

A two-stage bicycle exercise test with logarithmic intervals of load has been described, and the results reported in 760 patients. The test is now validated in a second group of 553 subjects. Performance data and FEV1 were available in all subjects and forced vital capacity in 366 of them. Regression equations of pulmonary function on work done stratified by sex and age were similar to those previously reported. Multiple regression showed that more than 57.8% of the variance could be explained in terms of vital capacity, height and age, with small contributions from weight and sex; with more than half being accounted for by vital capacity alone (R2 = 0.53). In an alternative equation predicted vital capacity, age (independently), percentage deficit of vital capacity below predicted, sex and weight/height2 explained 58.7% of the variance. In this approach, the percentage of vital capacity below predicted accounts for 25% of the variance after allowance for predicted vital capacity. It is confirmed that the first logarithmic stage of the test predicts a work rate that can be maintained for more than 5 minutes, producing a pulse rate of greater than 130 in two-thirds of the subjects. As the majority of those who failed to achieve this work rate had poor pulmonary function and were elderly, it is recommended that the second phase is set at a lower work load for these subjects.