Optimal Hydrostatic Loading for Closed-Circuit Underwater Breathing Apparatus Design
Technical rept. Jun-Sep 1988
NAVAL MEDICAL RESEARCH INST BETHESDA MD
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During the course of 3 shallow air-saturation dives, over 100 man- dives were made to 29 fsw with closed-circuit Underwater Breathing Apparatus UBA to test the effect of various hydrostatic loads on exercising divers. Both the MK-15 and EX-19 UBA were used. While in the erect sitting position, divers warmed-up for 5 min at 50 W, followed by 25 min of moderately heavy work 1.4 W kg on a submerged bicycle ergometer. Oxygen consumption, dyspnea score, and mouth pressure was continuously recorded. Three hydrostatic loads were presented to the divers by varying UBA position relative to the seated diver. Loads lay within and on either side of the current UBA hydrostatic loading specifications. All divers were able to complete work regardless of the hydrostatic load, and gave relatively low dyspnea scores. Subjectively, however, most divers preferred the median hydrostatic load, corresponding roughly to that at the suprasternal notch in an erect diver. The EX-19 UBA resulted in higher mouth pressures DP than the MK-15, which could be explained by the elastance of the EX-19. In spite of the higher DP, the EX-19 was preferred over the MK-15. The partitioning between inspiratory and expiratory pressure in both rigs was similar.
- Undersea and Antisubmarine Warfare