Bone changes due to hyperbaric exposure.

Based on the hypothesis that bone calcification is promoted by loading physical pressure, changes in the microstructure of the bone under hyperbaric conditions were analyzed by imaging technology. Hyperbaric exposure was carried out for two weeks at 2 atm (equal to the pressure at a depth of water of 10 m) which was achieved using a mixed gas of helium and oxygen (He:O2 88%:12%) in which the oxygen partial pressure was maintained at constant (PO2: 0.21 bar). In image technological analysis, the growth and development of the bone were evaluated at different stages using Digital Magnification Radiography (DMR) images and based on changes in the X-ray absorption ratio. DMR images after hyperbaric exposure showed calcification in the heads of long bones (humeri, femora, and tibiae) in mice. There were also significant changes in the X-ray absorption ratio in the heads. The accumulation of 99mTc-MDP was higher in all long-bone heads after hyperbaric exposure than before exposure. These results suggest that the hyperbaric environment promotes bone calcification.