Accession Number : ADA302468

Title :   Non-Linear Ascent Profiles Reduce the Risk of Decompression Illness After Deep No-Stop Dives.

Descriptive Note : Technical rept. Nov 94-May 95,

Corporate Author : NAVAL MEDICAL RESEARCH INST BETHESDA MD

Personal Author(s) : Broome, J. R.

PDF Url : ADA302468

Report Date : OCT 1995

Pagination or Media Count : 27

Abstract : The influence of no-stop ascent profile shape on decompression illness (DCI) risk after deep air and heliox dives was investigated using a swine model of neurological DCI. Following a simulated dive to 200 fsw for 24 min bottom time, while breathing air, pigs were decompressed over 10 min at either a linear 20 fsw/min, or on a non- linear fast-deep/slow-shallow profile. In the linear group, there were 11 cases of neurological DCI including 1 death and 8 cases with severe features, compared to 5 neurological DCI cases (1 severe) in the fast/slow group. 13/20 of the linear group versus 6/20 had moderate or severe skin DCI affecting >20% skin surface area. A similar study, but of paired, randomized, investigator-blind, sequential design was performed with pigs breathing 80/20% heliox. Pigs dived to 250 fsw for 8 min 50 5, then decompressed at either a linear 30 fsw/min rate, or on a fast/slow profile. Neurological DCI occurred significantly (p = 0.024) more frequently in the linear group (16/201 death and 11 severe) than in the fast/slow group (8/20; 3 severe). Moderate or severe skin DCI affected 16 of the linear group compared to 3 of the fast/slow group (p = 0.0002). The study findings suggest that, for deep no-stop diving, a non-linear fast-deep/slow-shallow ascent profile is safer than a linear rate of ascent, irrespective of breathing gas. This finding has the potential to reduce the risk of both military and civil diving operations.

Descriptors :   *STRESS(PSYCHOLOGY), *STRESS(PHYSIOLOGY), *DIVING, *DECOMPRESSION SICKNESS, *NEUROPHYSIOLOGY, MILITARY OPERATIONS, RISK, AIR, SEQUENCES, NONLINEAR SYSTEMS, PROFILES, LINEARITY, ILLNESS, RESPIRATION, CIVIL AFFAIRS, BREATHING GASES, SWINE, ASCENT TRAJECTORIES.

Subject Categories : Stress Physiology
      Psychology

Distribution Statement : APPROVED FOR PUBLIC RELEASE