Respiratory countermaneuvers in autonomic failure.

BACKGROUND Selective increase of inspiratory impedance augments blood pressure in healthy subjects through activation of the respiratory pump. We studied the efficacy of respiratory maneuvers to reduce orthostatic hypotension in autonomic failure. METHODS Mean arterial pressure (MAP) after standing up was recorded in 10 patients in five conditions: normal standing, leg muscle tensing, inspiratory pursed lips breathing, inspiratory sniffing, and a device causing inspiratory obstruction. RESULTS The maneuvers caused significant differences in standing MAP. Inspiratory obstruction and leg muscle tensing increased MAP to a comparable degree. The effect of inspiratory pursed lips breathing and inspiratory sniffing depended on concomitant hyperventilation. CONCLUSION Respiratory maneuvers reduce orthostatic hypotension in autonomic failure through activation of the respiratory pump, provided hyperventilation is avoided.