Application of Hyperbaric Oxygen Preconditioning to Improve Pilot′s Lower Body Negative Pressure Tolerance

Objective: To investigate whether the preconditioning of hyperbaric oxygen (HBO)can improve the tolerance of lower body negative pressure in pilots . Methods: Twenty healthy male fighter pilots were selected as subjects .The multiple HBO chamber was used and 3-time HBO exposure scheme was chosen .The chamber pressure was gradually increased to 2.5 atmospheres absolute （ATA） in 10 min and maintained for 65 min （with twice 30-min mask oxygen breathing and 5-min interval .Then the pressure was gradually reduced to 1.3 ATA in 10 min and returned to normal pressure in 5 min after staying for 5 min .Such 95-min test was undertaken once a day （set at 15:30--17:05） and repeated for 3 days .The lower body negative pressure tolerance was measured before and after HBO preconditioned and self-contrasted . Results: The cumulative stress index was significantly increased from(-1353.50±449 .95) to(-1843.50± 522 0.7) by 3 rounds HBO pretreatment （t =11.10，P<0.05） and it indicated that the lower body negative pressure tolerance had been improved . Conclusions: Hyperbaric oxygen preconditioning can improve the pilot’s lower body negative pressure tolerance