Intrapulmonary exchange of the stable isotope 18O2 injected intravenously in man

The stable isotope 18O2 was used to study the exchange of oxygen molecules between pulmonary capillary blood and alveolar gas in 16 patients with either normal lungs or limited lung disease. The technique entailed combining gaseous 18O2 with blood, then mixing the blood anaerobically with saline containing T-1824 dye and 85Kr in solution. After the combination of tracers had been injected into a vein, arterial blood was collected during the first passage of the indicators through the central circulation. Recoveries of the tracer gases were expressed as percentages of the amounts that would have been found had no loss from the blood stream occurred. The recoveries of 18O2 were related to the oxygen concentration in the inspired gas, and averaged 55, 40, and 11% at inspired concentrations of 14, 21, and 65%, respectively. The recovery of 85Kr was about 2%, and was independent of the inspired oxygen concentration. These results were compared to those predicted in a theoretical model, and found to agree satis...