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 (VE) and oscillating O(2) uptake (VO(2)) were calculated from several consecutive oscillations noted at rest, and compared with indices of CPX. Oscillating VO(2) preceded oscillating VE in 16 of the 17 patients. Peak VO(2) (10.3 ± 3.1 ml min(-1)kg(-1)) correlated significantly negatively with the cycle length of the VE oscillation (r=-0.60, P=0.010), and of the VO(2) oscillation (r=-0.61, P=0.008), and the difference in time between the peak of oscillating VE and the corresponding peak of VO(2) (r=-0.58, P=0.012). Similarly, the slope of the increase in VE to the increase in CO(2) output (45.6 ± 11.5) correlated significantly positively with the cycle length of the VE and VO(2) 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.
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 (VE) and oscillating O(2) uptake (VO(2)) were calculated from several consecutive oscillations noted at rest, and compared with indices of CPX. Oscillating VO(2) preceded oscillating VE in 16 of the 17 patients. Peak VO(2) (10.3 ± 3.1 ml min(-1)kg(-1)) correlated significantly negatively with the cycle length of the VE oscillation (r=-0.60, P=0.010), and of the VO(2) oscillation (r=-0.61, P=0.008), and the difference in time between the peak of oscillating VE and the corresponding peak of VO(2) (r=-0.58, P=0.012). Similarly, the slope of the increase in VE to the increase in CO(2) output (45.6 ± 11.5) correlated significantly positively with the cycle length of the VE and VO(2) 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.