An improved procedure for determination of cardiac output by a conductivity method

¹ Biomedical Laboratory, Aerospace Medical Division, Wright-Patterson AFB, Ohio; and Department of Physiology, Ohio State University, Columbus, Ohio

The applicability of the hematocrit dilution technique employing arterial blood conductivity changes to the determination of the cardiac output has been extended by a) electronic damping of the detecting circuits, which permits greater amplification of the signal without increasing the variability of the base line that occurs during each cardiac cycle, and by b) development of a solution isoosmolar and isoconductive with plasma that substitutes for autogenous plasma in the procedure. The preparation of the synthetic solution is described. It is shown that this solution gives results indistinguishable from those obtained with plasma. Values are given for the conductivity and osmolarity of dog plasma.