Effect of exposure to compressed air and elevated oxygen levels on bone blood flow in the rabbit.

As the pathogenesis of dysbaric osteonecrosis is not fully understood, we investigated the effects of compressed air, decompression, and elevated oxygen levels on bone blood flow. Bone blood flow was measured in 4 groups of rabbits using the radioactive-labeled microsphere technique. In the Control and Oxygen groups it was measured at normal pressure (1 ATA) at the end of 4-h exposures to air and 100% oxygen, respectively. In the Pressure group it was measured "at pressure" at the end of a 4-h exposure to compressed air (3 ATA) and in the Decompression group it was measured after decompression following a 3.5-h exposure to compressed air (3 ATA). Femoral head blood flow was significantly lower (P = 0.027) in both the Pressure (7.5 ml.100 g-1.min-1) and Decompression (7.1 ml.100 g-1.min-1) groups than in the Control group (13.0 ml.100 g-1.min-1). Moreover, the distribution of blood flow between the cortex and marrow of the humerus differed significantly (P = 0.044) between the Control and Pressure groups. No differences were found between the bone blood flow rates of the Control and Oxygen groups. It is concluded that femoral head blood flow is reduced by prolonged exposure to compressed air (without decompression) and that this is not solely an effect of the high partial pressure of oxygen.