RELATIONSHIPS OF TISSUE (SUBCUTANEOUS AND INTRAMUSCULAR) AND VENOUS PRESSURES TO SYNCOPE INDUCED IN MAN BY GRAVITY

Abstract

When subjects were tilted from the horizontal to the upright (75[degree]) position, there followed immediate and simultaneous rises in the venous pressure in the foot veins, the subcut. tissue pressure of the foot and the intramuscular pressure of the gastrocnemius. Subjects who did not develop syncope showed a secondary, usually more marked, increase in in-tramusc. pressure in the upright position, a change which was absent in those who showed circulatory embarrassment. Syncope never developed when intramusc. pressure was high and could be prevented by increasing the intramusc. pressure by muscular contraction. Venous and intramusc. pressure in the resting, horizontal position were found to be lower in individuals who developed postural syncope than in those who did not.