The effects of pre-breathing oxygen on hydrostatic weighing

Includes bibliographical references (pages 39-46)Twenty-four healthy male subjects, aged 18-41, were hydrostatically weighed using three different protocols to compare and analyze time submerged and percent fat results. Each submersion followed maximum exhalation. The protocols were: 3 minutes of breathing 100% oxygen from a 13.5 liter respiremeter, 3 minutes of breathing atmospheric air from the respirometer, and 3 hyperventilations of atmospheric air before submersion. Five traits were administered on each protocol. Pre-breathing 100% oxygen was found to significantly increase submersion times (p < .01).\ud Though no significant difference was found, the hyperventilation technique showed a trend toward improving submersion time over the atmospheric air protocol (p <.15). Interestingly, the comparison of underwater weights between the oxygen method and the other protocols initiated a curious sub-problem. Body density figures based on underwater scale readings in the oxygen trials, after 15-20 seconds of submersion, became significantly greater (p. < .01). No significant difference was found between percent fat calculated from mean oxygen scale readings and either hyperventilation or atmospheric air protocols. Though use of oxygen did not improve percent fat measurement for the skilled technician, pre-breathing 100% oxygen may prove useful with other populations and future investigations of changes in body density over submersion time