Carotid baroreflex heart rate control during the active and the assisted breathing cycle in man

Publisher Website
Google Scholar
Abstract
The interaction between the phase of the breathing cycle and the carotid baroreflex heart rate control was studied in 15 healthy subjects with special reference to respiratory sinus arrhythmia (RSA). Carotid baroreceptors were stimulated by neck suction. With a standardized breathing pattern, the following 2 types of experiment were performed. Neck suction was applied in counter phase with the respiratory arterial variations; this reduced the amplitude and shifted the phase of the transmural carotid arterial pressure oscillations but did not influence the RSA. During active and ventilator-assisted breathing, brief periods of neck suction were applied during inspiration (insufflation) or expiration. Neck suction during active inspiration did not change the amplitude of the RSA but when applied during expiration, increased it by 6.8 beats/min (P < 0.001). In the ventilator experiments, neck suction during insufflation and expiration augmented the RSA equally, by 5.3 beats/min (P < 0.05). A decreased sensitivity of the carotid arterial baroreflex during active inspiration, with no equivalent during assisted breathing, is indicated. The change in baroreflex sensitivity is evidently a prerequisite for the rise in the RSA.