CLINICAL STUDIES IN CIRCULATORY ADJUSTMENTS: VI. PHYSIOLOGIC RELATION BETWEEN POSTURE AND CARDIAC OUTPUT

When man assumed an upright posture he added appreciably to the adaptive needs of his circulation. New vasomotor regulations became necessary to counteract the effects of gravity. Inadequacies of these regulatory processes, whether congenital or acquired, are of importance to the clinician, who is confronted not infrequently with patients presenting untoward symptoms after a change in posture. Although the effects of gravity are greater on the venous than on the arterial side, there are so many factors which compensate for this primary effect on the venous return that the net change in the circulation produced by change in position can best be studied in terms of cardiac output. The reports in the literature on the effect of change of posture on cardiac output are so conflicting that a corroborative study of this subject by the highly satisfactory Grollman method was undertaken. MATERIAL AND METHOD In the present study (the sixth