The role played by the carotid sinus baroreflex in the genesis of the respiratory sinus arrhythmia (RSA) was studied in nine healthy subjects. The carotid sinus baroreceptors were stimulated by the application of subatmospheric to the neck. 2. Reducing the normal respiratory arterial pressure oscillations and changing the phase between the pressure oscillations and the respiration did not affect the RSA. 3. Stimuli applied during expiration only, augmented the arrhythmia, while inspiratory stimulation was without any effect. 4. It is suggested that changes in the arterial baroreflex set point and/or gain during the respiratory cycle contribute to RSA in man.
