Relation Between Oscillatory Breathing and Cardiopulmonary Function During Exercise in Cardiac Patients

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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 O₂ uptake (VO₂) were calculated from several consecutive oscillations noted at rest, and compared with indices of CPX. Oscillating VO₂ preceded oscillating VE in 16 of the 17 patients. Peak VO₂ (10.3±3.1mlmin^–1kg^–1) correlated significantly negatively with the cycle length of the VE oscillation (r=–0.60, P=0.010), and of the VO₂ oscillation (r=–0.61, P=0.008), and the difference in time between the peak of oscillating VE and the corresponding peak of VO₂ (r=–0.58, P=0.012). Similarly, the slope of the increase in VE to the increase in CO₂ output (45.6±11.5) correlated significantly positively with the cycle length of the VE and VO₂ 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.