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Voluntary control of breathing (CB) has been proposed as a means to standardize short-term investigations on cardiovascular variability (CVV). In this study, we assessed the changes induced by CB on ventilatory and cardiovascular parameters in 17 chronic heart failure (CHF) patients. We recorded the instantaneous lung volume (ILV), R-R interval (RR), systolic arterial pressure (SAP) and end-tidal CO/sub 2/ (ETCO/sub 2/, 10 patients only) during 8 minutes of spontaneous breathing (SB) and 8 minutes of CB at 0.22 Hz. CB caused a 14% reduction in respiratory rate, a 57% increase in tidal volume, a 27% increase in minute ventilation and a 7% decrease in ETCO/sub 2/. A negligible change was observed in mean RR and SAP. No significant change was observed in the low-frequency (LF) power of RR and SAP and in baroreflex sensitivity, whereas the high-frequency (HF) power increased markedly. Hence, CB in CHF patients causes a mild hyperventilation but does not seem to influence autonomic cardiovascular control. Only respiratory-related oscillations of CVV signals are affected by CB.

Non-invasive baroreflex sensitivity (BRS) by the classical transfer function (TF) method very often cannot be assessed in chronic heart failure (CHF) patients, due to a lack of coherence between the heart period and the systolic pressure. On the grounds of a previous investigation, we devised a new BRS index based on the whole-band average (WBA) of the TF in the whole low-frequency band (WBA-BRS), which does not require a coherence check. In this study, we assessed the clinical relevance of this index by testing its prognostic value in a population of 149 CHF patients. During a 20/spl plusmn/ 2 months follow-up, 28 patients died or were urgently transplanted. The univariate relation of the WBA-BRS index with mortality was assessed by the Cox proportional hazards model, and survival functions were estimated using the Kaplan-Meier method. We also investigated the independent effect of WBA-BRS, adjusting for the NYHA (New York Heart Association) class, LVEF (left ventricular ejection fraction), peak V/sub O2/ and Na/sup +/. WBA-BRS showed a significant univariate association with the risk of cardiac events. When its predictive value was assessed in multivariate analysis, WBA-BRS displayed independent prognostic information (risk ratio=3.0, 95% confidence interval: 1.1-7.9, p=0.03). These preliminary data suggest that BRS assessed by a modified version of the classical TF method is a potential prognostic marker in CHF patients.