Bilateral differences in forearm blood flow as measured with capacitance plethysmograph

Chester Hyman ¹, Donald Burnap ¹, and tpán Figar ¹

¹ Department of Physiology, University of Southern California, School of Medicine, Los Angeles, California and Institute of Physiology, Czechoslovak Academy of Sciences, Prague, Czechoslovakia

The electrocapacitance plethysmograph has been modified and tested for the measurement of blood flow through the forearm of normal, resting individuals. Data obtained indicate a small but consistent and significant difference between the blood flow of the two arms of a given individual at any time. This asymmetry is discussed and reasons are presented which make it seem likely that the differences are in blood flow through the skin rather than through muscle. The electrocapacitance plethysmograph was compared with the segmental plethysmograph in careful determinations on a group of subjects and it was found that the apparent blood flow as measured with the segmental plethysmograph tends to decrease as the pressure in the segmental cuff increases and that the differences between the blood flows in the two arms noted above becomes almost impossible to detect with segmental plethysmograph pressures above 15 mm Hg. When the capacitance plethysmograph is compared with the segmental plethysmograph inflated to minimal pressures in a series of acute measurements the correspondence is completely acceptable.