Respiratory and baroreceptor reflex interactions in man.

Respiratory and arterial baroreceptor reflex interactions were studied in six healthy young adults. Carotid baroreceptors were stimulated with two intensities of neck suction during early inspiration or expiration at 100 or 150% of each subject's normal tidal volume. Sinus node responses to moderate baroreflex stimuli were inhibited by inspiration, but responses to intense stimuli were not influenced by the phase of respiration. Supranormal tidal volume did not diminish responses to inspiratory baroreflex stimuli, but significantly reduced responses to expiratory stimuli. These results provide evidence for a central respiratory baroreceptor reflex interaction in man whose quality is dependent upon the level of afferent baroreceptor activity and the depth of inspiration.