Physiologic Response to Increased Oxygen Partial Pressure. Iii. Hematopoiesis.

The influence of increased partial pressure of oxygen on hematopoiesis was studied in 8 normal subjects: 4 subiects were exposed to a total pressure of 700 mm. Hg, 33 per cent 02 and 62.3 per cent N2; and 4 subjects to a total pressure of 258 mm. Hg, 98.5 per cent O2 and 0.2 per cent N 2. Two control subjects remained outside the chamber during each 3O-day study. Measurements were designed to determine whether the increased arterial P% (177.7 mm. Hg in the 700 mm. Hg group, and 169.7 mm. Hg in the 258 mm Hg group) affected circulating red blood cells and/or red blood cell production. Except for mild changes in red cell values with hematocrit reduction of 6.7 per cent and 9.1 per cent in the 700 mm. Hg group and 258 mm. Hg group, respectively, most of the hcmatopoietic studies were normal. It appears that 3O-day exposure to the increased oxygen partial pressures used in this study does not significantly alter hematopoiesis. Capt. Zalusky is from Applied Radiobiology Branch, Bionudeonics Department, USAF School of Aerospace Medicine, Brooks AFB, Texas. Dr. Ulvedal is from Sealed Environment Section, Environmental Systems Branch, Bioastronautics Department, USAF School of Aerospace Medicine, Brooks AFB, Texas. Capt. Herlocher is Chief, Sealed Environment Section, Environmental Systems Branch, USAF School of Aerospace Medicine, Brooks AFB, Texas. Dr. Welch is Chief, Environmental Systems Branch, Bioastronautics Department, USAF School of Aerospace Medicine, Brooks AFB, Texas. This work was supported in part by NASA Office of Advanced Research and Technology (NASA-Defense PR No. R-89) and Manned Spacecraft Center, NASA (NASA-Defense PR No. T-16758-G). 622 Aerospace Medicine 9 July 1964 H YPOXIA ACTS AS a potent stimulator of rex[ blood cell production in the mammal. Most evidence indicates that this stimulus is mediated through a humoral factor, erythropoietin, lr On the other hand, there are relatively few studies concerning the influence of increased oxygen concentration on erythropoiesis. Conflicting data exists suggesting that hypoxia may either suppress 7, 8, 16, 18 or have little influence e on red blood cell production. In an occasional report, an increase in red cell values has been noted. TM Because of pulmonary pathology resulting from excessively high oxygen concentrations, the latter have been attributed to relative hypoxemia. We had the opportunity to study erythropoiesis in a group of healthy young subjects who were being maintained in an environment of increased oxygen concentration for one month. From practical considerations, it became important to determine whether the proposed gaseous environment would have any adverse influence on hematopoiesis during prolonged space flight. The studies were designed to estimate whether hyperoxia of this degree would have a deleterious effect on circulating red blood cells, resulting in a hemolytic anemia, or, perhaps more importantly, whether suppression of erythropoiesis occurs resulting in the gradual development of anemia through the normal attrition of senescent red cells.