The Association between Low CO₂ Production and Central Sleep Apnea in Men with Heart Failure

Rationale: Hunter-Cheyne-Stokes breathing with central sleep apnea (CSA) is prevalent in some patients with heart failure with reduced ejection fraction (HFrEF). Theoretical models of Hunter-Cheyne-Stokes breathing predict that a low metabolic rate (MR) predisposes one to CSA. Objectives: In this study, we examined the role of MR in the pathogenesis of CSA. Methods: A physiological study was conducted in a sleep laboratory at a U.S. Department of Veterans Affairs medical center. Patients were 28 consecutive male Veterans with stable HFrEF. After an adaptation night, polysomnography, left ventricular ejection fraction, pulmonary function tests, carbon dioxide production ([Formula: see text]), and arterial blood samples were obtained under strict standardized conditions. Physiological variables were then entered into regression models to examine the association with CSA. Results: Body mass index varied from 20 to 40 kg/m², and [Formula: see text] ranged from 167 to 434 ml/min. In the final regression model, low [Formula: see text] and low body mass index were associated with CSA index. [Formula: see text] had the strongest association (95% confidence interval, -0.36 to -0.06; P = 0.007). Conclusions: In patients with HFrEF, a low MR and related low [Formula: see text], but not low oxygen consumption, were associated with CSA. Mechanistically, in the face of low MR and [Formula: see text], a given change in ventilation results in large swings in partial pressure of CO₂, thus promoting CSA. To our knowledge, this is the first study in humans that shows this association.