Transcapillary Migration of Heavy Water and Thiocyanate Ion in the Pulmonary Circulation of Normal Subjects and Patients With Congestive Heart Failure 123

During recent years numerous investigations have been concerned with the rates of transfer or exchange of various substances across capillary beds (1-6).These studies, by analyzing curves of disappearance over several minutes from ar- terial plasma of intravenously injected tracer sub- stances, have provided some information relative to all capillary beds combined.However, this type of experiment has not permitted a close analy- sis of the behavior of a substance during its first passage through a single organ capillary bed.Recently developed techniques (7-9) now per- mit the clinical investigator to examine the phe- nomena of transcapillary exchange of water and other diffusible substances in local vascular areas.This study was undertaken in an attempt to de- termine in vivo the diffusion characteristics of the pulmonary capillary bed in man with regard to deuterium oxide and an electrolyte, thiocyanate ion.Seven normal subjects and seven patients with pulmonary congestion due to heart failure were studied.The resulting data relating to the pul- monary capillaries were then compared to those previously obtained using similar tracer substances in the capillaries of the human forearm (7).