Submarine rescue decompression procedure from hyperbaric exposures up to 6 bar of absolute pressure in man: effects on bubble formation and pulmonary function.

Recent advances in submarine rescue systems have allowed a transfer under pressure of crew members being rescued from a disabled submarine. The choice of a safe decompression procedure for pressurised rescuees has been previously discussed, but no schedule has been validated when the internal submarine pressure is significantly increased i.e. exceeding 2.8 bar absolute pressure. This study tested a saturation decompression procedure from hyperbaric exposures up to 6 bar, the maximum operating pressure of the NATO submarine rescue system. The objective was to investigate the incidence of decompression sickness (DCS) and clinical and spirometric indices of pulmonary oxygen toxicity. Two groups were exposed to a Nitrogen-Oxygen atmosphere (pO2 = 0.5 bar) at either 5 bar (N = 14) or 6 bar (N = 12) for 12 h followed by 56 h 40 min resp. 60 h of decompression. When chamber pressure reached 2.5 bar, the subjects breathed oxygen intermittently, otherwise compressed air. Repeated clinical examinations, ultrasound monitoring of venous gas embolism and spirometry were performed during decompression. During exposures to 5 bar, 3 subjects had minor subjective symptoms i.e. sensation of joint discomfort, regressing spontaneously, and after surfacing 2 subjects also experienced joint discomfort disappearing without treatment. Only 3 subjects had detectable intravascular bubbles during decompression (low grades). No bubbles were detected after surfacing. About 40% of subjects felt chest tightness when inspiring deeply during the initial phase of decompression. Precordial burning sensations were reported during oxygen periods. During decompression, vital capacity decreased by about 8% and forced expiratory flow rates decreased significantly. After surfacing, changes in the peripheral airways were still noticed; Lung Diffusion for carbon monoxide was slightly reduced by 1% while vital capacity was normalized. The procedure did not result in serious symptoms of DCS or pulmonary oxygen toxicity and may be considered for use when the internal submarine pressure is significantly increased.

MRI features of spinal cord decompression sickness presenting as a Brown-Sequard syndrome.

Decompression sickness often manifests as central nervous system impairment. We report a 49-year-old woman who developed an unusual case of spinal cord decompression sickness presenting as complete Brown-Sequard syndrome. Initial MRI revealed increased signal intensity in the left side of the cervical cord at the level of C2-C3. A second MRI at 10 days post-injury showed signal abnormalities corresponding to an infarction in the posterior spinal artery territory. After two weeks of intensive treatment with various HBOT regimens, the clinical outcome was still poor, but at six months after the injury her neurological condition was greatly improved, with only slight impairment of proprioception on the left when walking remaining.

Descriptive epidemiology of 153 diving injuries with rebreathers among French military divers from 1979 to 2009.

INTRODUCTION: Rebreathers are routinely used by military divers, which lead to specific diving injuries. At present, there are no published epidemiologic data in this field of study. METHODS: Diving disorders with rebreathers used in the French army were retrospectively analyzed since 1979 using military and medical reports. RESULTS: One hundred and fifty-three accidents have been reported, with an estimated incidence rate of 1 event per 3,500 to 4,000 dives. Gas toxicities were the main disorders (68%). Loss of consciousness was present in 54 cases, but only 3 lethal drowning were recorded. Decompression sicknesses (13%) were exclusively observed using 30 and 40% nitrox mixtures for depth greater than 35 msw. Eleven cases of immersion pulmonary edema were also noted. CONCLUSION: Gas toxicities are frequently encountered by French military divers using rebreathers, but the very low incidence of fatalities over 30 years can be explained by the strict application of safety diving procedures.

[Current management of diving-related spinal cord decompression sickness in 2010]. / Prise en charge des accidents de décompression médullaire en plongée sous-marine : actualités en 2010.

The outcome of spinal cord decompression sickness after scuba diving is unpredictable during the 24 first hours with a high risk of incomplete recovery. The treatment is defined on first aid normobaric oxygen when neurological symptoms occur, rehydration and prompt recompression in hyperbaric chamber. The presence of initial motor impairment, the aggravation of symptoms during the transfer to the hyperbaric facility and the emergence of sphincter dysfunction are predictive of poor prognosis whatever the treatment undertaken.

Bubble incidence after staged decompression from 50 or 60 msw: effect of adding deep stops.

OBJECTIVES: The French Navy uses the Marine Nationale 90 (MN90) decompression tables for air dives as deep as 60 msw. The resulting incidence of decompression sickness (DCS) for deep dives (45-60 msw) is one case per 3000 dives. METHODS: Three protocols with experimental ascent profiles (EAPs) were tested in the wet compartment of a hyperbaric chamber. For each protocol, eight subjects dove to 50 or 60 msw and ascended according to the standard MN90 table or an EAP. Precordial bubbles were monitored with Doppler sensors at 30-min intervals after surfacing. Protocol I went to 60 msw and used deep stops beginning at 27 msw. Protocol II was a repetitive dive to 50 msw with a 3-h surface interval; the EAP made the first deep stop at 18 msw. Protocol III again went to 60 msw, but the EAP used a single, shorter deep stop at 25 msw. RESULTS: For Protocol I, all divers developed bubbles at Spencer grade 2-3 and still had bubbles 120 min after surfacing; there was no statistical difference between bubbling for the MN90 and EAP, but one diver presented a case of DCS after the EAP. For Protocol II, the EAP produced severe bubbling for the eight divers. Those findings led to stopping the EAPs with the longer deep stops used in Protocols I and II. Protocol III again showed no difference between the standard and modified profiles. DISCUSSION: The addition of deep stops requires careful consideration. Two of our EAPs made no difference and one produced increased bubbling.