Contribution of the Lung to the Genesis of Cheyne‐Stokes Respiration in Heart Failure: Plant Gain Beyond Chemoreflex Gain and Circulation Time

BACKGROUND: The contribution of the lung or the plant gain (PG; ie, change in blood gases per unit change in ventilation) to Cheyne‐Stokes respiration (CSR) in heart failure has only been hypothesized by mathematical models, but never been directly evaluated. METHODS AND RESULTS: Twenty patients with systolic heart failure (age, 72.4±6.4 years; left ventricular ejection fraction, 31.5±5.8%), 10 with relevant CSR (24‐hour apnea‐hypopnea index [AHI] ≥10 events/h) and 10 without (AHI <10 events/h) at 24‐hour cardiorespiratory monitoring underwent evaluation of chemoreflex gain (CG) to hypoxia ([Formula: see text]) and hypercapnia ([Formula: see text]) by rebreathing technique, lung‐to‐finger circulation time, and PG assessment through a visual system. PG test was feasible and reproducible (intraclass correlation coefficient, 0.98; 95% CI, 0.91–0.99); the best‐fitting curve to express the PG was a hyperbola (R (2)≥0.98). Patients with CSR showed increased PG, [Formula: see text] (but not [Formula: see text]), and lung‐to‐finger circulation time, compared with patients without CSR (all P<0.05). PG was the only predictor of the daytime AHI (R=0.56, P=0.01) and together with the [Formula: see text] also predicted the nighttime AHI (R=0.81, P=0.0003) and the 24‐hour AHI (R=0.71, P=0.001). Lung‐to‐finger circulation time was the only predictor of CSR cycle length (R=0.82, P=0.00006). CONCLUSIONS: PG is a powerful contributor of CSR and should be evaluated together with the CG and circulation time to individualize treatments aimed at stabilizing breathing in heart failure.