Submarine Rescue Decompression Procedure from Hyperbaric Exposures up to 6 Bar of Absolute Pressure in Man: Effects on Bubble Formation and Pulmonary Function

Abstract

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.

Scientific shallow saturation dive expedition using diving rebreathers and a specific dry habitat: medical management of the “Capsule” programme

“…However, oxygen may be toxic with acute neurological toxicity and long-term effects on lungs [22]. This model driven by oxygen appear effective as previously suggested by Kot [23] in Nitrox saturation dives or Blatteau et al [24] without VGE detection and non-significant spirometric alteration. Procedures were based on the COMEX database which allowed the development of regulatory procedures in professional diving in France and the REPEX oxygen toxicity threshold [22,25].…”

The Extended Oxygen Window Concept for Programming Saturation Decompressions Using Air and Nitrox

“…Interestingly, the systems published by the US Navy went in an opposite direction, allowing faster ascent rates for deeper saturation depths [ 4 ]. It is evident that none of the existing systems require or suggest really fast ascent in the first phase of decompression, namely through the EOW, just using the constant rate of decompression [ 4 , 11 , 44 , 46 – 49 ].…”

“…Such knowledge could be of great value also for practical use of the model for planning of saturation decompressions in case of emergency, when high partial pressure of oxygen is empirically used for accelerating desaturation. Some modeling research has already been done [ 55 ], some studies on animals have been conducted [ 56 ], several procedures have been recommended [ 57 , 58 ], and recently, this method has been investigated in humans [ 11 , 59 ]. Even if “the advantages of oxygen appear far less than predicted by current decompression models” [ 60 ], using a high amount of oxygen for accelerating decompression is already recommended in case of emergency [ 55 , 61 ].…”

“…Nevertheless, the trial and error approach has led to a successful definition of operational procedures, and has practically “eradicated” DCS from saturation exposures, which moved diving companies away from research on physiology of saturation and decompression. However, we recently observed that some large organizations are reviving studies in this field [ 11 ] (M. Gennser, personal communication). Therefore, we decided to present the complete set of data for the first time, which had been used for the creation of the Polish system of air and nitrox saturation decompressions using the novel concept of the Extended Oxygen Window .…”

Effects of hyperbaric nitrogen-induced narcosis on response-selection processes

“…They gave written informed consent according to the declaration of Helsinki. This study was a part of a series of experiments at the French Army Hyperbaric Centre [for more details, see our previous article (Blatteau et al 2013)]. The experimental protocol was approved by both the scientific committee for the protection of human subjects (CPP Sud Mediterranée I, ref.…”