Mechanism of diuresis during negative pressure breathing

¹ Department of Physiology, University of Buffalo School of Medicine and the Cardio-Renal Laboratory of the Edward J. Meyer Memorial Hospital, Buffalo, New York

The diuresis associated with negative pressure breathing in moderately hydrated man is found to be due chiefly to an increase in the excretion of free water; solute excretion rises slightly and consistently. Simultaneous clearance studies do not reveal a characteristic pattern in renal hemodynamics for diuresis is observed to attend an increase, decrease or absence of change in RPF and GFR. There is, moreover, no effect on the peripheral venous hematocrit nor on the osmolar concentration of the plasma. Negative pressure breathing is without effect on urine flow when performed during maximal water diuresis or during the antidiuresis produced by infused Pitressin. These observations are in accord with the theory that the effective mechanism for the diuresis of negative pressure breathing is a reflex inhibition of antidiuretic hormone secretion.