Decompression advantages of trimix
Berghage, T.E.; Donelson, C.; Gomez, J.A.
Undersea Biomedical Research 5(3): 233-242
1978
ISSN/ISBN: 0093-5387 PMID: 705940 Document Number: 124410
For saturation exposures, animal studies have demonstrated that breathing mixtures of multiple inert gases provide no more protection against decompression sickness than breathing mixtures of He-O2. The differential gas-exchange characteristics of N and He could provide a decompression advantage for short-duration dives, if the gases were mixed in the proper proportions. To evaluate this possibility, 700 albino rats were exposed to 2 pressure levels (7 and 16.2 ATA ), 5 exposure times (5, 15, 30, 60 and 120 min) and 5 inert gas combinations (He/N, percent: 0/100, 25/75, 50/50, 75/25 and 100/0). The O2 partial pressures were kept constant at 0.51 ATA. During each pressure exposure 5 rats were exercised in a rotating cage. After the pressure exposures the animals were rapidly decompressed to a lesser pressure (1 or 4.9 ATA, depending on the exposure pressure) for a 30 min observational period. O2 partial pressure during the observation period was maintained at 0.2 ATA. The incidence of pain-only decompression sickness (bends) noted at the end of this period was the dependent measure. The use of multiple inert gas combinations can facilitate decompression for short-duration dives. The optimum combination of inert gases was related to the exposure time (P < 0.005): the relative concentration of He was increased as exposure time was lengthened.