The total carbonate content of the arterial and venous plasma in normal individuals

Abstract

In the course of some observations on the respiratory disturbances seen in certain diseased conditions it became necessary for the sake of comparison to determine the total carbon dioxide of the arterial and venous plasma in individuals with normal cardio-respiratory mechanisms. In all the bloods of nineteen normal individuals at rest have been examined. In each case samples of arterial and venous blood were obtained within a few minutes of each other.

Method.—The arterial blood was obtained by direct puncture of the radial artery using a technique similar to that employed by Stadie. 1 The venous blood was collected without stasis from one of the large veins at the bend of the elbow. To avoid contact with air both samples were carefully delivered under albolene into paraffin coated centrifuge tubes and immediately centrifuged at high speed. One c.c. of the separated plasma was delivered under carbonate free ammonia water contained in a receiving cup of the Van Slyke apparatus and the total Co₂ content determined by the method devised by Van Slyke.¹ The method adopted was considered to be more advantageous for my purpose than the widely used method of first exposing plasma to 5.5 per cent. of CO₂ and ascertaining the CO₂ combining power.

Results: The results presented in the accompanying table indicate that the total CO₂ content of the arterial plasma is a fairly constant figure, averaging fifty-six volumes per cent. The venous plasma is always a little higher than the arterial in individual cases, the discrepancy being from three to eight volumes per cent. This discrepancy has been found to increase if the individual is allowed to take some light exercise, such as walking, just before the blood samples are taken.