EFFECT OF BREATHING PATTERN ON BLOOD-PRESSURE AND HEART-RATE OSCILLATIONS IN HUMANS

1. The relationships of respiratory sinus arrhythmia (RSA) and respiratory changes in systolic blood pressure (SBP) to tidal volume (V(T)) and breathing frequency (BF), were quantified during voluntary control of V(T) and BF in healthy subjects. 2. Respiration was measured non-invasively with a respiratory inductive plethysmograph, which was calibrated prior to each study while breathing through a pneumotachygraph. Finger arterial blood pressure was measured non-invasively by the Finapres. 3. Heart rate (HR) increased during inspiration, with a nearly fixed time delay for most V(T) and BF approximating 0.9 s. The magnitude of RSA increased with increases in V(T) and with decreases in BF. SBP decreased during inspiration, with a time delay which increased as BF decreased, resulting in a phase delay approximating 160-degrees. The magnitude of the inspiratory fall in SBP increased with increases in V(T). Increased amplitudes of RSA and SBP variation occurred at the lowest BF, consistent with the possibility of interactions between respiratory-related influences and those due to slow waves' of vasomotor tone. 4. The present results are consistent with the conclusion that respiratory effects on SBP are caused by a mechanism other that simply changes in HR.