Valsalva's maneuver revisited: A quantitative method yielding insights into human autonomic control

Seventeen healthy supine subjects, performed graded Valsalva maneuvers. In four objects, transesophageal echographic aortic cross-sectional area decreased during and after straining. During the first seconds of straining, when aortic cross-sectional areas was declining and peripheral arterial pressure was rising, peroneal sympathetic muscle neurons were nearly silent. Then, as aortic cross-sectional area and peripheral pressure both declined, sympathetic muscle nerve activity increase, in proportion to the intensity of straining. Poststraining arterial pressure elevations were proportional to preceding increases of sympathetic activity. Sympathetic inhibition after staining persisted must longer than arterial and right atrial pressure elevations. Similarly, R-R intervals ~45 s after the onset of straining, when R-R intervals were greater and arterial pressures were smaller than prestraining levels. Our conclusions are as follows: opposing changes of carotid and aortic baroreceptor inputs reduce sympathetic muscle and increase vagal cardiac motor neuronal firing; parallel changes of barosensory inputs provoke reciprocal changes of barosensory inputs provoke reciprocal changes of sympathetic and direct changes of vagal firing; and pressure transients lasting only seconds reset arterial pressure-sympathetic and -vagal response relations.