Background: The importance of exercise capacity as an indicator of
prognosis in patients with heart disease is well recognized. However,
factors contributing to exercise limitation in such patients have not
been fully characterized and in particular, the role of lung function in
determining exercise capacity has not been extensively investigated.
Objective: To examine the extent to which pulmonary function and
respiratory muscle strength indices predict exercise performance in
patients with moderate to severe heart failure. Methods: Fifty stable
heart failure patients underwent a maximal symptom-limited
cardiopulmonary exercise test on a treadmill to determine maximum oxygen
consumption (VO2max), pulmonary function tests and maximum inspiratory
(PImax) and expiratory (PEmax) pressure measurement. Results: In
univariate analysis, VO2max correlated with forced vital capacity (r =
0.35, p = 0.01), forced expiratory volume in 1 s (r = 0.45, p = 0.001),
FEV1/FVC ratio (r = 0.37, p = 0.009), maximal midexpiratory flow rate
(FEF25-75, r = 0.47, p < 0.001), and PImax (r = 0.46, p = 0.001), but
not with total lung capacity, diffusion capacity or PEmax. In stepwise
linear regression analysis, FEF25-75 and PImax were shown to be
independently related to VO2max, with a combined r and r(2) value of
0.56 and 0.32, respectively. Conclusions: Lung function indices overall
accounted for only approximately 30% of the variance in maximum
exercise capacity observed in heart failure patients. The mechanism(s)
by which these variables could set exercise limitation in heart failure
awaits further investigation