Tissue gas tensions in experimental anemia

¹ Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire

"Tissue-venous" O₂ and CO₂ tensions were determined by the subcutaneous gas pocket technique in rats with induced anemia of varying severity. Correlative ventilatory and metabolic measurements were made under light anesthesia. Gas pocket CO₂ tension remained unchanged in all animals, but O₂ tension decreased in anemic animals. Making use of the gas pocket tensions, rat blood nomogram, and certain assumptions, largely supported by the other measurements, a number of physiological values were calculated. From these it was concluded that in the anemic animal alveolar ventilation remained unchanged but, in the region of the gas pocket, blood flow increased with every decrement of hemoglobin concentration below the normal value. There was no "threshold" concentration of hemoglobin below normal at which point the blood flow response was initiated—the response was a continuous one. An in vivo slope value of the CO₂ blood dissociation curve was derived and this was shown to vary directly with the hemoglobin concentration. Finally, the rate of disappearance of gas from the subcutaneous pocket suggested that there was a diffusion factor, in addition to blood flow, which played a role in the rate process.

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