Relation between oscillatory breathing and cardiopulmonary function during exercise in cardiac patients

Abstract

Background: Oscillatory breathing, alternating between hyperpnea and hypopnea, has been recognized in cardiac patients, especially in those with heart failure. We evaluated whether the cycle length and amplitude of oscillatory breathing correlate with impaired cardiopulmonary function during exercise. Methods and Results: We analyzed respiratory gas data during cardiopulmonary exercise testing (CPX) in 17 cardiac patients (68±12 years) who showed clear oscillatory ventilation during CPX. The cycle length (time from peak to peak) and the amplitude (difference between peak and nadir) for both oscillating ventilation (V̇ E) and oscillating O2 uptake (V̇O2) were calculated from several consecutive oscillations noted at rest, and compared with indices of CPX. Oscillating V̇O2 preceded oscillating V̇ E in 16 of the 17 patients. Peak V̇O2 (10.3±3.1 ml · min-1 ·; kg-1) correlated significantly negatively with the cycle length of the V̇ E oscillation (r=-0.60, P=0.010), and of the V̇O2 oscillation (r=-0.61, P=0.008), and the difference in time between the peak of oscillating V̇ E and the corresponding peak of V̇ O2 (r=-0.58, P=0.012). Similarly, the slope of the increase in V̇ E to the increase in CO2 output (45.6±11.5) correlated significantly positively with the cycle length of the V̇ E and V̇O2 oscillations (r=0.68, P=0.002; r=0.67, P=0.003, respectively). Conclusions: The cycle length of oscillatory breathing is closely related to impaired cardiac reserve during exercise in cardiac patients.