OBSERVATIONS ON AUTONOMIC PARTICIPATION IN PULMONARY ARTERIOLAR RESISTANCE IN MAN 1

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Abstract
15 patients were studied with a double lumen cardiac catheter, and simultaneous measurements of the pulmonary artery and pulmonary "capillary" pressures were made, using the Hathaway strain gauges and recording apparatus. Simultaneous ecgs., ballistocardiograms, and brachial arterial tracings were recorded, and cardiac outputs were also measured by the direct Fick method. Resting values were obtained and the measurements repeated after 5 or 6 mg. tetraethyl ammonium chloride (TEAC)/kg. body wt. had been admd. intraven., and the max. effect had been obtained on the brachial arterial pressure, usually within 3 to 5 min. Mean pressures were detd. from the recordings by planimetric integration, and pulmonary resistance and total peripheral resistance before and after TEAC were calculated in dynes sec. cm.-5 according to standard formulae. In 11 of 15 subjects, intraven. TEAC produced a sustained fall in pulmonary arterial pressure. However, in 4 patients with normal pulmonary artery pressure, TEAC intraven. did not lower pulmonary arteriolar resistance while in 6 cases with pulmonary hypertension, a significant decrease in pulmonary arteriolar resistance was noted. Since it is known that the tetraethylammonium ion blocks transmission in autonomic ganglia, these results suggest that in some cases of pulmonary hypertension, at least one component of the increased pulmonary arteriolar resistance is mediated through the autonomic nervous system. The effect of TEAC on cardiac output was variable, and the development of an abnormal ballistocardio-graphic pattern after TEAC in 4 of 5 subjects suggests a direct cardiac action of the drug in man. Although a decline in mean brachial artery pressure followed the admn. of TEAC intraven. in each of 14 subjects, the fall in 4 of them was due to a decreased cardiac output rather than to a diminished peripheral resistance.