Submarine Escape Research Articles

Exposure levels for carbon monoxide in nuclear submarine atmosphere

This work proposes exposure limits for carbon monoxide in the nuclear submarine environment. Linear and non-linear forms of the Coburn-Foster-Kane equation were used to evaluate carbon monoxide exposure for an environment with low oxygen content, different exposure times and crew physical activity levels. We evaluated the 90-day Continuous Exposure Guidance Level, 24-h and 1-h Emergency Exposure Guidance Levels and 10-day and 24-h Submarine Escape Action Levels. The results showed that the concentration of carbon monoxide in the environment must not exceed 9 ppm for the 90-day Continuous Exposure Guidance Level, 35 ppm for the 24-h Emergency Exposure Guidance Level, 90 ppm 1-h Emergency Exposure Guidance Level, 60 ppm for the 10-day Submarine Escape Action Level and 80 ppm for the 24-h Submarine Escape Action Level. Comparing these values with those established by the National Research Council for the United States Navy, the limits proposed by this work are verified to be lower, which may indicate a risk to the health of the crew. They also show the impact of the crew's level of physical activity on the formation of carboxyhemoglobin.

Pneumothorax during manned chamber operations: A summary of reported cases

In-chamber pneumothorax has complicated medically remote professional diving operations, submarine escape training, management of decompression illness, and hospital-based provision of hyperbaric oxygen therapy. Attempts to avoid thoracotomy by combination of high oxygen partial pressure breathing (the concept of inherent unsaturation) and greatly slowed rates of chamber decompression proved successful on several occasions. When this delicate balance designed to prevent the intrapleural gas volume from expanding faster than it contracts proved futile, chest drains were inserted. The presence of pneumothorax was misdiagnosed or missed altogether with disturbing frequency, resulting in wide-ranging clinical consequences. One patient succumbed before the chamber had been fully decompressed. Another was able to ambulate unaided from the chamber before being diagnosed and managed conventionally. In between these two extremes, patients experienced varying degrees of clinical compromise, from respiratory distress to cardiopulmonary arrest, with successful resuscitation. Pneumothorax associated with manned chamber operations is commonly considered to develop while the patient is under pressure and manifests during ascent. However, published reports suggest that many were pre-existing prior to chamber entry. Risk factors included pulmonary barotrauma-induced cerebral arterial gas embolism, cardiopulmonary resuscitation, and medical or surgical procedures usually involving the lung. This latter category is of heightened importance to hyperbaric operations as an iatrogenically induced pneumothorax may take as long as 24 hours to be detected, perhaps long after a patient has been cleared for chamber exposure.

Buoyant ascent rate profiles for the MK10 and MK11 submarine escape and immersion equipment

Introduction: Since the U.S. Navy transitioned from the MK10 to the MK11 submarine escape and immersion equipment (SEIE) there has been an increase in the incident rate of pulmonary barotrauma during submarine escape training. This study compares ascent rate profiles of the MK10 and MK11 SEIE to determine if ascent rate differences between the escape suits are associated with an increase in pulmonary barotraumas. Methods: Buoyant ascent rates of the MK10 and MK11 SEIE were compared using weighted manikins equivalent to the 1st, 50th, and 99th percentile body weight of a submariner. Human ascents using the MK11 (n=126) were compared to human ascents in the same trainer wearing the MK10 (n=124). Results: Manikin mean ascent times were faster for the MK10 compared to the MK11 (5.19 seconds vs 5.28 seconds, p < 0.05). Terminal velocity (Vt) was affected by manikin weight (p < 0.001). Human trials confirmed the manikin results. The average mean ascent velocity for the MK10 group was 0.155 meters/second faster than the MK11 group mean ascent velocity (p < 0.001). Mean ascent velocity was inversely correlated with all anthropometrics for the MK10 group (p < 0.01). Neither height nor body mass index showed a significant association with mean ascent velocity for the MK11 group. Conclusions: The Vt of buoyant ascents are significantly affected by body weight. As the mean ascent rate of the MK11 is slower than that of the MK10, ascent rate profile differences between the suits do not appear to explain the recent increase in pulmonary barotrauma incident rates during escape training.

Research on game strategy of underwater attack and defense process in typical situation

Aiming at the problem of underwater attack and defense in typical situations, a mathematical model of three-party attack and defense problem composed of torpedo, submarines and anti-torpedo torpedo is established. Under the condition of considering three-party game confrontation, the three-party game problem is transformed into the pursuit and escape game problem between the submarine and torpedo, and the interception and evasion game problem between the submarine launched ATT and the torpedo. Based on the optimal control theory and differential game theory, the three-party optimal game problem is studied, and the three-party game performance evaluation function is designed based on the optimal performance of the two parties of pursuit and escape and the two parties of interception and evasion. According to the optimal necessary condition of the bilateral extremum, the strategy of pursuing, escaping, blocking and avoiding in the three-party game is deduced. The effectiveness of the game strategy designed in the underwater attack and defense process is verified by simulations. The results show that the game strategy can improve the effects of submarine escape, anti-torpedo torpedo interception and torpedo attack.

Effects of different simulated submarine escape depths by free ascent in animal models.

Objective: If a damaged submarine cannot be rescued in time, it is necessary to carry out a submarine escape by free ascent. Decompression illness is the greatest threat to the safety of submariners. The maximum depth at which a safe escape can be carried out is unknown. This study intends to explore the maximum safe escape depth by observing the effects of simulated submarine escape at different depths on animal models. Methods: We evaluated pulmonary function indexes, blood gas values, blood cell counts, the myocardial enzyme spectrum, coagulation parameters, and proinflammatory cytokine levels in rats, electrocardiographic activity in rabbits after simulated 150-m, 200-m, 220-m, and 250-m submarine escape by free ascent. Results: An escape depth of 150m did not cause significant changes in the indicators. An escape depth of >200m led to pulmonary ventilation and gas diffusion dysfunction, hypoxemia, myocardial ischemia, and activation of the fibrinolytic and inflammatory systems. The magnitudes of the changes in the indicators were proportional to escape depth. Conclusion: An escape depth of 150m in animal models is safe, whereas escape at > 200m can be harmful.

What does the Historical Record Say about the Chances of Surviving an Escape from a Disabled Submarine?

IntroductionDespite US Navy and international Disabled Submarine (DISSUB) rescue capabilities, escape remains an important means of DISSUB crew survival as the crew may be forced to conduct an escape before rescue assets arrive on site due to adverse conditions onboard or operational or engineering constraints that may render rescue impossible. The main aims of the current study were to conduct an analysis of historical DISSUB records to describe the likely biomedical evolution of crew survivability following the disabling of a submarine in shallow waters, in order to develop a casualty estimate and define the main risks to escapee survival.MethodsFrom unclassified historical and scientific publications, we collated and categorized international DISSUB events in which escape was effected or attempted by any part of the crew, dating from the earliest documented DISSUB escape in 1851 until September 2019. Both non‐combat and combat sinkings were included. We also reviewed at‐sea submarine escape trial experience and medical incidents from US Navy pressurized submarine escape training records to estimate air embolism and extra‐alveolar air casualties and fatalities during escape training. Our analysis identified the casualty risk for DISSUB survivors for the following three phases: (1) survival in the submarine before escape, (2) survival during the escape ascent, and (3) survival on the surface.Results & ConclusionsUsing historical data from a total of 437 attempted DISSUB escapes that included 37 accidental and combat submarine sinkings, the following observations were made: The largest number of casualties occurred during the onboard survival phase due to atmospheric toxicity. 72% of the submariners who attempted an escape survived the escape. Escapes have been successful from a DISSUB as deep as 240 feet sea water (fsw) and experimentally during at sea submarine escape trials from depths down to 600 fsw. All historical escapes were effected within the current 72‐hour time to first rescue timeframe, with the majority occurring within 4 hours of DISSUB onset. The majority of escapees who survived were recovered from the water within 60 min. Early rescue surface response mobilization and detailed crew knowledge of escape equipment, procedures, and the physiological phenomena encountered under increased and changing pressures are essential to enhance escapee survivability. US Navy submarine escape training records indicated very low risk (<0.5%) of pulmonary over inflation syndrome or arterial gas embolism and no fatalities during the past 11 years of pressurized escape training.

Case Series of Arterial Gas Embolism Incidents in U.S. Navy Pressurized Submarine Escape Training From 2018 to 2019.

The goal of Pressurized Submarine Escape Training (PSET) is to prepare future submariners for the physical and mental challenges of escaping a disabled submarine and promote proper handling of the Beaufort Ltd Mk 11 Submarine Escape and Immersion Equipment suit. Training participants are only permitted to enter PSET after strict health screening protocols have been met to optimize trainees' safety. Before PSET, trainees are given detailed, one-on-one instruction on proper ascent mechanics by specially trained Navy Dive instructors. Since the reinstatement of PSET by the U.S. Navy, four incidents of arterial gas embolism (AGE) have occurred in submarine trainees with a 10-year period (2009-2019). Of these four incidents, three were observed within a couple months of each other from 2018 to 2019. A comprehensive review of AGE history, epidemiology, dive physiology, pathophysiology, and management was completed. Prompted by the recent incidents relative to the low reported incidence rate of AGE in historical PSET training, reported potential risk factors were compared with better understand potential etiologies of AGE in already medically screened individuals. Risks and benefits of PSET were listed, compared, and analyzed. The relative safety and cost effectiveness of this rigorous form of training was reconfirmed.

Decrease in dysbaric osteonecrosis severity as a result of 45-minute oxygen pre-breathe

Sudden decompression can result in bubble formation as the result of nitrogen gas (N2) dissolved in tissue during disabled submarine escape (DISSUB). This may cause dysbaric osteonecrosis (DON), a condition in long bones where bubbles in fatty marrow result in ischemia and necrosis. Previous research has shown that oxygen (O2) pre-breathe of two hours resulted in a reduction of DON; however, effects of shorter O2 pre-breathe remain uncertain. This study’s aim was to understand the effect of shorter lengths of O2 pre-breathe. Eight adult Suffolk ewes (89.5± 11.5 kg) were exposed to 33 feet of seawater (fsw) for 24 hours. They were placed randomly into four groups and exposed to either 45, 30 or 15 minutes of O2 (91-88%) pre-breathe; the controls received none. They were then rapidly decompressed. Alizarin complexone was later injected intravenously to visualize the extent of DON in the right and left long bones (radii, tibiae, femur and humeri). The 30- and 15-minute pre-breathe groups saw the greatest deposition. There was significant decrease of variance in the 45-minute group when compared with all other treatments, suggesting that 45 minutes of O2 pre-breathe is required to effectively increase confidence in the reduction of DON. Similar confidence was not reflected in the 30-minute and 15-minute groups: 45 minutes of pre-breathe was the minimum amount needed to effectively prevent against DON in DISSUB escape at 33 fsw. However, future research is needed to determine how to calculate effective dosages of O2 pre-breathe to prevent DON in any given scenario.

A Study on the Breakage of the Hatch Spring of the Submarine Escape Trunk through Microstructure Analysis

A Study on the Breakage of the Hatch Spring of the Submarine Escape Trunk through Microstructure Analysis

An echo from the past: Building a Doppler repository for big data in diving research

Decompression sickness (DCS) remains a major operational concern for diving operations, submarine escape and high-altitude jumps. Aside from DCS symptoms, venous gas emboli (VGE) detected with ultrasound postdive are often used as a marker of decompression stress in humans, with a specificity of 100% even though the sensitivity is poor [1]. Being non-invasive, portable and non-ionizing, ultrasound is particularly suited to regular and repeated monitoring. It could help elucidate interand intra-subject variability in VGE and DCS susceptibility, but analyzing these recordings remains a cumbersome task [2].

Decrease in Dysbaric Osteonecrosis Lesions as a Result of 45‐minute Oxygen Pre‐breathe

IntroductionNitrogen (N2) dissolved in long bone fatty marrow can lead to bubble formation in tissue when exposed to sudden decompression. During a disabled submarine escape (DISSUB) hastened decompression is often necessary, and formation of bubbles is likely. If recompression is not administered in a timely manner, bubbles may lead to ischemia and necrosis of marrow and bone, a condition called Dysbaric Osteonecrosis (DON). Oxygen (O2) pre‐breathe has been proposed as a way to reduce N2 in tissue, thus decreasing risk of DON. Previous research has shown that O2 pre‐breathe of 2‐hours resulted in a reduction in DON; however, effects of shorter O2 pre‐breathe are uncertain. This study’s aim is to understand the effect of shorter durations of O2 pre‐breathe on DON formation.MethodEight adult Suffolk ewes (89.5 ± 11.5 kg) were exposed to 33 feet of seawater (fsw) for 24 hours. Animals, separated at random into four groups (n=8) and exposed to either 45, 30, or 15 minutes of O2 (91–88%) pre‐breathe and 21% (controls), were rapidly decompressed. Four weeks after exposure and two weeks prior to euthanasia, Alizarin Complexone was injected intravenously to visualize areas of DON. Right and left long bones (radii, tibiae, femora, and humeri) were analyzed to determine the extent of Alizarin Complexone deposition. Percent deposition in the proximal, middle and distal thirds, as well as over the entire bone was calculated using areas of deposition and total bone to determine for extent of DON. Variance between the groups was found using an unpaired t‐test and Welch’s correction.ResultsA decrease in variance of DON occurrence was seen in the radius when comparing the 45‐minute (min) group to the 30‐min, 15‐min and the controls (p < 0.0001). The humerus also showed a similar decrease in variance when comparing groups (p < 0.05). Both the femur and tibia saw decreases in variance when comparing 45‐min group to the 30‐min and 15‐min group, (p < 0.0005) however no reduction was seen between the 45‐min group and the controls. The radius and tibia saw the highest rates of lesions. The radius mean depositions were 0.05 ± 0.07 in the 45‐min group, 4.8 ± 5.0 in the 30‐min group, 13.2 ± 14.8 in the 15‐min group and 6.4 ± 12.4 for the controls. The tibia mean depositions were 0.13 ± 0.18 in the 45‐min group, 4.8 ± 6.0 in the 30‐min group, 6.8 ± 11.2 in the 15‐min group and 0.6 ± 0.4 for the controls.DiscussionThe 30‐min, 15‐min and controls showed significant amounts of variability, which we hypothesize is due to differences in body composition. Similarly in humans, DON appears sporadically in those exposed to rapid decompression. The decrease of variance in the 45‐min group suggests that 45 minutes of O2 pre‐breathe is required to effectively increase confidence in the reduction of DON. Similar confidence was not reflected in the 30‐min and 15‐min groups. During DISSUB, speed of evacuation is vital for survival, our data suggests a minimum of 45 minutes of pre‐breathe is needed to confidently reduce the risk of developing DON. However, this duration may vary based on depth, time, body mass and bone composition. Future research is needed to understand the relationship between these variables in order to effectively calculate the sufficient O2 pre‐breathe required for an individual.Support or Funding InformationSupported by NAVSEA N00024‐17‐C‐4318

Identifying Predictors of Pressurized Submarine Escape Training (PSET) Attrition.

Pressurized Submarine Escape Training (PSET) physically prepares submariners to safely escape a submarine at depth. Failure to complete PSET is not a submarine service disqualification. Serious medical incidents are rare, but the safety record tradeoff has been low throughput. From 2009 to 2015, only 34% of students screened completed PSET. Students may be medically screened out of the training altogether (disqualified), or dropout during the physical training (attrite). Training records from 12,122 U.S. Navy students were used to identify factors contributing to training disqualification and attrition. Multivariate logistic regression model predictors included demographic and screening items. Association to PSET disqualification included cold/congestion/cough (ORadj 12.34), limited duty status (ORadj 4.29), Physical Readiness Test failure (ORadj 3.37), pneumonia or bronchitis in last 2 years (ORadj 3.17) and nervousness or anxiety in tight spaces (ORadj 2.37). Basic Enlisted Submarine School students were more likely to be disqualified and attrite than other submariner groups, and black/African American (ORadj 1.53) students were more likely to attrite than white students. Only cold/congestion/cough (ORadj 1.52), trouble swimming (ORadj 1.53), and screening during cold/flu season (ORadj 1.28), were associated with training attrition. Recommendations to modify screening requirements are listed in conclusions.

Psychological considerations in submarine escape training: brief overview and future directions.

The inability of a submarine to surface must rate as one of greatest risks to sailors in peacetime. To prepare for such emergencies, many navies provide training to master the procedures required to escape successfully from disabled submarines. This paper provides a brief overview of some of the psychological principles in simulated submarine escape training. It further discusses applicable psychological constructs such as positive outcome expectancies, the role of anxiety, and other personal factors mediating outcomes of such training. It concludes with recommendations for future research aimed at enhancing the safety and impact of submarine escape training. These include enhanced detection of psychological risk factors such as anxiety, as well as investigating the relative contribution of personality variables to in-training safety and positive outcome expectancies. These recommendations do not only apply to submarine escape training, but may also be applicable to high fidelity safety training in other off-shore survival contexts, such as helicopter underwater escape training, freefall lifeboat training and smoke diving.

First Aid Oxygen Treatment for Decompression Illness in the Goat After Simulated Submarine Escape.

Personnel responding to a distressed submarine incident require information on likely casualty levels and the severity and progression of decompression illness (DCI). Recompression may not be immediately available. First aid oxygen (FAo₂) can be administered; however, there is no direct evidence of its efficacy in this scenario. Trials were conducted between 2004 and 2006. Goats exposed to raised pressure for 24 h ('saturation') were either returned directly to atmospheric pressure (Phase A, N = 40) or exposed to simulated submarine escape at a depth of 656 ft (200 m; assumed seawater density = 1019.72 kg · m(-3); Phase B, N = 39). The pressure during saturation was selected to provoke 50% DCI. Cases of DCI were randomly assigned to receive FAo₂or air. DCI cases were: limb pain in 39 subjects, neurological in 6, respiratory in 4, and pulmonary barotrauma in 1 subject. In Phase A, 5/12 subjects in the FAo₂group and 0/11 in the air control group achieved permanent resolution of DCI. In Phase B, 6/8 subjects in the FAo₂group and 5/8 in the air control group achieved permanent resolution. In both Phases, levels of venous gas bubbles reduced sooner with FAo₂. Of three cases of neurological DCI receiving FAo₂, two showed permanent resolution. In total, four cases of respiratory DCI occurred; none of these resolved, with three being treated with FAo₂and one in the air control. Oxygen can be an effective first aid measure for DCI following submarine escape. However, it should not be used as a replacement for recompression therapy.

Injury Rate in a Helicopter Underwater Escape Trainer (HUET) from 2005–2012

Helicopter underwater escape training (HUET) carries a potential for injury and this paper identifies the injury rate. A marine survival training school registry of all students trained between 2005-2012 in HUET and the coinciding accident records were examined. There were 8902 students trained in a helicopter underwater escape simulator for a total of 59,245 underwater escapes. There were 40 cases where only first-aid was required and 3 serious injuries (a laceration requiring 5 sutures, 1 dislocated shoulder, and 1 water aspiration requiring hospitalization). There were no deaths and no problems reported with using the Emergency Breathing System (EBS) or Air Pocket. Of the injuries, 11 were due to the student using a poor escape technique. The overall probability of injury was 0.74 per 1000 ascents. In HUET training, there is a very low injury rate with almost no significant severity. Although not scientifically proven, this would suggest that the low incident rate is due to good medical screening and the attention given by instructors to anxious students. Compared to other training such as diving, parachute jumping, and submarine escape training, the rate of injury was considerably lower.

The research progress of diving medicine in P.R. China

Diving medicine is one of the branches of military medicine, and plays an important role in naval development. This review introduces the progress of researches on undersea and hyperbaric physiology and medicine in the past few years in China. The article describes our research achievement in conventional diving and its medical support, researches on saturation diving and its medical support, submarine escape and its medical support, effects of hyperbaric environments and fast buoyancy ascent on immunological and cardiological functions. Diving disorders (including decompression sickness and oxygen toxicity) are also introduced.

Conceptual Design and Optimization of Submarine Escape Capsule

Submarine escape capsule is an effective equipment to improve submariners viability when accident. In order to design a reasonable escape system, three alternatives, sphere chamber, ellipsoid chamber and combined chamber, were presented in the conceptual design process. The factors which influenced decision making were researched subsequently, such as general performance parameters, dependence on submarines position when releasing, safety of the product in hazardous conditions and the products influence on submarine. Then the influenced factors and their attributes were evaluated in three alternatives, and a multiple attribute decision making approach based on entropy weight was used to optimize the conceptual design. The results showed that combined chamber was the best choice for submarine escape capsule because its overall technology level was superior to others.

Acute Neurological Symptoms During Hypobaric Exposure: Consider Cerebral Air Embolism

Cerebral arterial gas embolism (CAGE) is well known as a complication of invasive medical procedures and as a risk in diving and submarine escape. In the underwater environment, CAGE is caused by trapped air, which expands and leads to lung vessel rupture when ambient pressure decreases during ascent. Pressure decrease also occurs during hypobaric activities such as flying and, therefore, CAGE may theoretically be a risk in hypobaric exposure. We reviewed the available literature on this subject. Identified were 12 cases of CAGE due to hypobaric exposure. Based on these cases, we discuss pathophysiology, diagnosis, and treatment of CAGE due to hypobaric exposure. The low and slow pressure decrease during most hypobaric activities (as opposed to diving) account for the low incidence of CAGE during these exposures and suggest that severe air trapping must be present to cause barotrauma. This is also suggested by the large prevalence of air filled cysts in the case reports reviewed. We recommend considering CAGE in all patients presenting with acute central neurological injury during or shortly after pressure decrease such as flying. A CT scan of head and chest should be performed in these patients. Treatment with hyperbaric oxygen therapy should be initiated as soon as possible in cases of proven or probable CAGE.

Brain oxygenation and CNS oxygen toxicity after infusion of perfluorocarbon emulsion

Intravenous perfluorocarbon (PFC) emulsions, administered with supplemental inspired O(2), are being evaluated for their ability to eliminate N(2) from blood and tissue prior to submarine escape, but these agents can increase the incidence of central nervous system (CNS) O(2) toxicity, perhaps by enhancing O(2) delivery to the brain. To assess this, we infused a PFC emulsion (Oxycyte, 6 ml/kg iv) into anesthetized rats and measured cerebral Po(2) and regional cerebral blood flow (rCBF) in cortex, hippocampus, hypothalamus, and striatum with 100% O(2) at 1, 3, or 5 atmospheres absolute (ATA). At 1 ATA, brain Po(2) stabilized at >20 mmHg higher in animals infused with PFC emulsion than in control animals infused with saline, and rCBF fell by ~10%. At 3 ATA, PFC emulsion raised brain Po(2) >70 mmHg above control levels, and rCBF decreased by as much as 25%. At 5 ATA, brain Po(2) was ≥159 mmHg above levels in control animals for the first 40 min but then rose sharply; rCBF showed a similar profile, reflecting vasoconstriction followed by hyperemia. Conscious rats were also pretreated with PFC emulsion at 3 or 6 ml/kg iv and exposed to 100% O(2) at 5 ATA. At the lower dose, 80% of the animals experienced seizures by 33 min compared with 50% of the control animals. At the higher dose, seizures occurred in all rats within 25 min. At these doses, administration of PFC emulsion poses a clear risk of CNS O(2) toxicity in conscious rats exposed to hyperbaric O(2) at 5 ATA.

Intravenous Perfluorocarbon After Onset of Decompression Sickness Decreases Mortality in 20-kg Swine

Decompression sickness (DCS) occurs when bubbles form due to pressure decreases with severity ranging from trivial to fatal. Standard treatment requires a hyperbaric chamber, not likely to be available at remote sites or during a disabled submarine escape or rescue. Alternative (non-recompressive) treatments are needed. Intravenous administration of emulsified perfluorocarbons (PFCs) enhances oxygen delivery to, and inert gas removal from, tissues. Swine studies show PFCs administered with supplemental oxygen before symptom onset can decrease DCS incidence. We used a swine model to test whether PFC plus supplemental oxygen could improve outcome when infused after DCS symptom onset. After rapid decompression from 31 min at 200 fsw (7.06 ATA) animals were observed for signs of DCS. Upon DCS onset animals received 100% 02 and were randomized to receive either saline or PFC. Oxygen administration was continued for 1 h and the primary outcomes of mortality and/or abnormal gait were noted 24 h after surfacing. PFC significantly improved survival, with 18/25 (72%) PFC treated animals and 13/29 (45%) saline treated animals alive at 24 h post-exposure. Objective measures of stance/gait trended toward improvement; spinal cord lesions correlated with severity of stance/gait abnormalities. PFC administered after DCS onset improved survival in this 20-kg swine model. Further study into the mechanisms of benefit and delayed DCS therapy are warranted.