Naval Sea Systems: Optimizing performance during topside operations and diving at altitude

Principal Investigator: Dave Hostler, PhD

Funding Agency: Naval Sea Systems

Abstract: U.S. military ground operations can be conducted at medium and high altitude, such as in Iraq and Afghanistan. Mission needs can require personnel to be flown immediately to altitude without time for adjustment or adaptation. One of the normal physiological compensations of altitude is hyperventilation to preserve blood oxygenation. The increase in respiratory work provides some protection against altitude-related disease but can also impair performance due to respiratory muscle fatigue. Problems can quickly develop on land with exercise, but can also be seen underwater should diving activity be required. While hypoxia is eliminated with increasing ambient pressure, the respiratory fatigue may make the high work of breathing associated with diving more difficult to tolerate, leading to additional performance compromise. This problem is independent of the increased decompression stress associated with altitude diving. In previous work from our laboratory, respiratory muscle training (RMT) was shown to increase respiratory strength and endurance making respiration more effective and extending exercise performance as much as 68% at the surface and as much as 86% at a depth of 120 fsw. There is little information available on the decompression stress of divers working at altitude, particularly diving that begins immediately upon arrival. This proposal will examine the effects of RMT on performance during topside operations at altitude and during diving at altitude. It will also explore the decompression strain that occurs after diving at altitude by assessing venous gas bubbling after diving at 3658 m (12,000 ft.) of altitude.