[Effects of simulated 100 m Trimix conventional diving on oxidative stress and inflammatory reaction in rabbits].

OBJECTIVE: To investigate the effects of simulated 100 m Trimix conventional diving on tissue inflammatory cytokines in rabbits. METHODS: Eight New Zealand rabbits were performed a simulated 100 m Trimix conventional diving program which was established according to the Haldane theory. The expression levels of interferon-gamma(IFN-γ), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-8 (IL-8), myeloperoxidase(MPO) and matrix metallo proteinase-9 (MMP-9) in rabbits lung and brain tissues were detected by Elisa after diving decompression. The tissue wet/dry ratio was calculated. The serum levels of superoxide dismutase (SOD),glutathione(GSH), catalase(CAT), malondiadehyde(MDA) and lipid peroxide(LPO) were detected by Elisa method in rabbits before and after diving. RESULTS: The expressions of IFN-γ, TNF-α, IL-6, IL-8, MPO and MMP-9 in simulated diving group rabbits were significantly increased compared with the intact group(P<0.05, P<0.01); the simulated diving rabbits tissues wet/dry ratio had no significant changes compared with the intact group. After diving, the activities of SOD and GSH were decreased significantly (P<0.01), while the contents of CAT, MDA and LPO were increased significantly (P<0.01). CONCLUSIONS: The simulated 100 m Trimix conventional diving had significant impact on oxidative stress and inflammatory reaction in rabbits, the results of wet/dry ratio showed that the diving rabbits had no tissue edema after decompression.

Simulated High Altitude Helium-Oxygen Diving.

BACKGROUND: Experience with commercial heliox diving at high altitude is limited. The purpose of this study was to evaluate the effects of acute high-altitude exposure on fitness to dive and the safety of decompression after heliox diving while using U.S. Navy heliox decompression tables with Cross correction. METHOD: Four professional male divers were consecutively decompressed in a hypo- and hyperbaric chamber to altitudes of 3000 m (9842.5 ft), 4000 m (13,123.4 ft), and 5200 m (17,060.4 ft) during the 8-d study. The dive profiles tested were to 30 m (98.4 ft) for 60 min at all three altitudes and, in addition, a dive to 50 m (164 ft) for 60 min at 5200 m altitude. The decompression followed the U.S. Navy heliox decompression table. The safety of decompression was evaluated by precordial Doppler venous gas emboli (VGE) monitoring during the decompression stages and postdive monitoring of the divers for symptoms of decompression sickness (DCS). Effects of altitude exposure were measured as subjective rating and EEG signs of sleepiness and fatigue, clinical symptoms of high altitude disease, and fitness to dive. RESULTS: A total of 24 person-dives were conducted. There were no VGE detected during the decompression and no postdive symptoms of decompression illness. Both the EEG findings and subjective evaluation indicated increased sleepiness and fatigue at 3000 m, 4000 m, and 5200 m, all compared with the sea level baseline. During the diving phase, both the EEG findings and subjective evaluation scores returned to the baseline and the divers successfully completed diving. DISCUSSION: Diving at high altitude with a short acclimatization period appears safe despite divers exhibiting clinical symptoms and EEG signs of impairment by hypoxia at high altitude. Despite a small number of dives, the results of this study indicate that our application of U.S. Navy standard heliox decompression tables with Cross correction is effective and could be used for underwater constructions up to 5200 m altitude, with due caution.Shi L, Zhang Y, Tetsuo K, Shi Z, Fang Y, Denoble PJ, Li Y. Simulated high altitude helium-oxygen diving. Aerosp Med Hum Perform. 2017; 88(12):1088-1093.

[Calculation of underwater decompression schedule for the simulated 100 m Trimix conventional diving and verification of the schedule with animal experiment].

OBJECTIVE: To explore the underwater decompression schedule for 100 m Trimix conventional diving operations and evaluate its safety through a simulated rabbits Trimix conventional diving. METHODS: According to the Haldane theory, the assumed time units, the classification of tissue compartments, the nitrogen super-saturation safety coefficient and the selection of methods used for the calculation of the simulated 100 m Trimix conventional diving schedule were properly selected, and the calculating method for the dive decompression schedule was thus firmly established. In our experiments, five tissue compartments were selected during the calculation of decompression schedule: 5 min, 10 min, 20 min, 40 min and 75 min, and the nitrogen super-saturation safety coefficient was calculated by 1.6. Eight New Zealand rabbits were performed a simulated 100 m Trimix dive program which was established according to the Haldane theory, and eight rabbits for intact group. The tissues wet/dry ratio and ethology were detected and observed before and after the simulated diving to evaluate the safety of decompression schedule. RESULTS: By using the developed underwater decompression schedule, abnormal ethology changes in rabbits could not be observed after compression and decompression to the surface; and the tissues wet/dry ratio of simulated diving rabbits had no significant changes compared with the intact group (P > 0.05). CONCLUSION: The decompression schedule calculated by Haldane theory seemed to be safe and reliable, the diving breathing gas concentration did not cause oxygen toxicity and nitrogen narcosis among the dive rabbits, and dive efficiency was greatly improved by using enriched oxygen gas in UPTD safety range during decompression.