Man-Trial of the Twenty-First Century Surface-Supplied Heliox (He-O2) Decompression Table
Abstract
The Surface-Supplied Helium-Oxygen (SS He-O2) Decompression Table in the current U.S. Navy Diving Manual (Revision 7, Change A) is an edited version of an original 1939 issue with a limited record of success in operational dives to depths of 240 feet sea water (fsw) or shallower. Recent theoretical evaluations indicate that schedules in this table, intended for longer and deeper dives that are becoming increasingly within the scope of desired U.S. Navy diving operations but have a limited historical usage, present unacceptably high risks of decompression sickness (DCS). Navy Experimental Diving Unit (NEDU) generated two tables of schedules with an updated linear-exponential multi-gas (LEM) probabilistic model to incur 2.3% maximum estimated risks of DCS as candidates to replace the current SS He-O2 Decompression Table. The second of these tables included a modification to accommodate a +/- 0.5% gas mixing error allowed in the U.S. Navy Diving Manual. 232 simulated man-dives were completed in the NEDU Ocean Simulation Facility by 56 diver-volunteers on 20 different depth/time schedules selected from the candidate tables. In 91 man-dives completed on the unmodified schedules, two cases of DCS Type II occurred and one case of surface interval pain occurred that resolved by the time of arrival at the 50 fsw first surface decompression chamber stop. In 141 man-dives completed on the modified schedules, one case of marginal DCS Type I occurred and one case of surface interval pain occurred that resolved by the time of arrival at the 50 fsw first surface decompression chamber stop. Pooling results from all 232 completed man-dives and omitting cases of surface interval pain that resolved within minutes of arrival at the first surface decompression chamber stop, as per provisions in the protocol, DCS incidence in this trial was 1.3% (3/232), from which it was inferred at 95% binomial confidence that the actual DCS risk of the schedules is less than 3.3%.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2023
- Accession Number
- AD1215313
Entities
People
- David J. Doolette
- David M. Sherrier
- F. G. Murphy
- Wayne A. Gerth
Organizations
- United States Navy Experimental Diving Unit