RESPIRATION AND BLOOD-PRESSURE VARIABILITY - MECHANICAL AND AUTONOMICINFLUENCES

The transfer function between broad-band respiratory activity and the heart rate (HR) response can be used to elucidate the frequency depend ent phase and magnitude characteristics of the respiratory sinus arrhy thmia (RSA)(1). To understand the complex links between respiratory ac tivity and arterial blood pressure (ABP), the transfer functions betwe en instantaneous lung volume (ILV), parameters of arterial pressure, a nd central venous pressure (CVP) were determined in healthy human volu nteers during 6-minute periods in which the respiratory rate was volun tarily controlled in a predetermined but erratic fashion, or CVP was p erturbed with a similar pattern. Pharmacologic autonomic blockade was used to dissect the direct mechanical links between respiration and AB P from the effects of RSA on ABP. The results suggest that with HR flu ctuations eliminated, respiration affects ABP in proportion to the rat e of change of ILV; however, when neural control of HR remains intact, the RSA plays an important role in the genesis of ABP fluctuations.