Altered cardiorespiratory control in patients with severe congestive heart failure: a transfer function analysis approach

The role of respiration in controlling central venous return and cardiac output was investigated in 5 patients with congestive heart failure (CHF) before and after therapy and 7 controls. Transfer function analyses were performed to quantify respiratory sinus arrthymia (RSA), arterial baroreflex gain, and the mechanical influence of respiration, during spontaneous and random interval breathing. CHF patients had markedly reduced RSA and arterial baroreflex gain compared to controls, resulting in minimal HR variability at frequencies above 0.05 Hz. HR variability was preserved in 3/5 CHF patients at frequencies below 0.05 Hz, and was associated with periodic breathing and oscillations of systolic blood pressure (SBP) and central venous pressure (CVP), which improved with therapy. In addition, CHF subjects had alterations of the mechanical link between respiration and central venous pressure which were normalized in some patients by therapy. Transfer function analysis can provide insight into circulatory regulation and therapy effects in CHF patients.