An aqueous solution of tritium and krypton 85 together with Evans blue dye was injected intravenously in twelve normal subjects during quiet breathing, during apnea, and during voluntary hyperventilation. Arterial blood was sampled within the first 30 sec after the injection to measure the recovery of the two gases. Blood-gas partition coefficients of the two gases at 37 C were determined experimentally and the ratio between them was found to be 3.8 in normal blood. Knowing this ratio it is possible to calculate the fraction of the arterial recovery due to a right-to-left shunt, and that due to alveolar back pressure. The shunt calculated from findings during quiet breathing is 0.26% of the cardiac output. Recoveries during apnea lead to a calculated shunt of identical size, whereas the shunt calculated from the experiments during hyperventilation amounts to only 0.11% of the cardiac output.
Submitted on March 8, 1962
- Copyright © 1962 the American Physiological Society