Postural Changes in Blood Distribution and Its Relation to the Change in Cardiac Output

Abstract

Cardiac output and the blood content indices of the several parts of the body were measured in 18 subjects including patients with various diseases using external radioisotope counting techniques. Changes in these 2 parameters induced by standing were compared with each other. Average changes in blood distribution produced by standing were as follows. Decrease in blood content in the "lung" ([long dash]25%) and in the "heart" ([long dash]26%) and increase in the "thigh" (+56%) were statistically significant. No significant change was revealed in the "head", "palm". "liver" and "abdomen". Cardiac output and stroke volume decreased by standing in most of the cases. Recent data were added to those reported previously and were treated statistically. Average decrease in cardiac output was[long dash]13% in 6 control cases, [long dash]35% in 16 cases with neurocirculatory asthenia and [long dash]35% in 10 cases with hyper-thyroidism. The difference was significant between control and neurocirculatory asthenia. Standing induced a substantial increase in cardiac output in a case of idiopathic nodal rhythm, although there remains a doubt whether it is the ordinary response in this disease. Significant linear correlation was revealed between per cent change of blood content in the "thigh" or in the "lung" and that of cardiac output or stroke volume induced by standing. Minimal blood shift was observed when the latter was extreme, and vice versa. This implies as follows reactivity of the heart might be influenced by posture, and transmural pressure of veins and/or capillaries is probably adjusted, as in arterioles, to compensate for changes in cardiac output.