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 the ascent rate profiles of the MK10 and MK11 SEIE to determine if ascent rate differences between the escape suits are associated with increased 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 than 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's 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 is 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.

Submarine medicine: An overview of the unique challenges, medical concerns, and gaps.

Submariners face many challenges. For example, they "live where they work" and can be called to duty anytime. They have limited access to open space, natural settings, fresh air, fresh food, sunlight, privacy, exercise, and outside communication. They support a wider range of missions than occur aboard most other Navy vessels. At sea or on shore, submariners work long hours under conditions with little margin for error. They may traverse remote or disputed areas of the ocean far from rescue assets, and must remain vigilant for potential encounters with hostile forces, onboard fires, anomalies in the breathing atmosphere, leaks, undersea collisions, or radiation exposures. If any of these factors cause casualties, the Independent Duty Corpsman (with intermittent advice from shore-based medical personnel), must be ready to provide aid as long as necessary. The challenges of submarine service led to the growth of the unique field of submarine medicine, which has maintained an excellent record of health and safety. This review introduces the field of submarine medicine as practiced in the U.S. Navy, describing its major concerns, giving an overview of the operation of a submarine medical department, and identifying several medical gaps that researchers are working to fill. Submarine medicine already has a stellar record in terms of radiation and atmospheric safety and has made strides in fatigue management. Ongoing work will deliver improved psychological screening and support tools. This report summarizes developments in these and other areas of submarine medicine.

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.

Altered Sex Ratios in Offspring of U.S. Submariners Urban Legend or Fact - Do Submariners Have More Daughters?

INTRODUCTION: There is a widespread and long-held belief in the submarine community that submariners father more daughters than the general population. The U.S. Sex Ratio at birth (males/females) has remained around 1.05 since the early 2000s. Limited evidence exists that certain environmental exposures including chemicals, heavy metals, radiation and g-forces may influence sex ratio at birth. A reduction in male births in a population has been associated with lower male fertility. A 1970 single site study showed a higher ratio of female offspring in personnel serving aboard U.S. Navy nuclear submarines than the general population. A 2004 study concluded that this was probably not true. However, this study was small, and did not evaluate the difference between children conceived during sea duty versus shore duty. They did note a higher chance of female offspring correlated with a longer time in the community, as well as an increased ratio in sonar technicians. These findings warrant further investigation. METHODS: An electronic survey was e-mailed to submariners, after receiving required IRB and Navy approvals. Participants were asked birth year, year they entered submarine service, and how many children they had. For each child they were asked sex, child's birth year, mother's birth year, and whether they were on sea duty or shore duty at the time of conception. Those who were on sea duty at the time of conception were asked what their job was, where they were stationed and what type of submarine they were on. Those who were on shore duty at the time of conception were asked whether they were in contact with submarines on a regular basis, whether they were officer or enlisted, and what region they were stationed in for shore duty. RESULTS: Four thousand eight hundred responses were received with a total of 6,958 children included in the analysis. Respondents had a SR of 0.95 compared to 1.05 U.S. population in 2015 (p < 0.0001). Submariners on sea duty had a SR of 0.88 compared to 1.02 on shore duty (p = 0.007). Those who had regular submarine contact on shore duty had a SR of 0.72 compared to 1.17 in those who did not (p < 0.001). Geographical location during shore duty did show differences that were statistically significant (p = 0.018). Geographical location during sea duty did not show significant differences. No significant differences were seen for paternal age, maternal age, job during sea duty, type of submarine assigned to or time in community. CONCLUSION: The submariners surveyed reported greater numbers of daughters than the general population, especially when on sea duty or in regular contact with submarines during shore duty. Further study should be done to confirm results and explore possible etiologies of differences in sex ratio.

Submarine exposure guideline recommendations for carbon dioxide based on the prenatal developmental effects of exposure in rats.

BACKGROUND: To protect crewmember health, the U.S. Navy sets exposure limits for more than 200 components of submarine atmospheres. The addition of females to nuclear submarines required a reevaluation of these exposure limits, originally established for all-male crews. In the case of carbon dioxide (CO2 ), the only available data suitable for deriving an exposure limit were from a 2010 study sponsored by the British Royal Navy that reported a debatable interpretation casting doubt on whether current U.S. Navy exposure limits served to protect fetal developmental health. METHODS: About 120 time-mated female Sprague-Dawley rats (Crl: CD[SD]) were exposed to CO2 at levels of 1.5%, 2.0%, 2.5%, and 3.0% from gestation days 6 to 20. Dams were euthanized and fetuses were examined. RESULTS: Findings with implications for exposure limits for CO2 during pregnancy were an increased mean litter proportion of early resorptions and a lower mean litter proportion of viable fetuses in the 3.0% CO2 group. CONCLUSION: The results yield a No Observed Adverse Effect Level (NOAEL) of 2.5% and a Lowest Observed Adverse Effect Level (LOAEL) of 3.0%. The results reasonably allow a point of departure of 2.5% CO2 for deriving an exposure recommendation. An interspecies uncertainty factor was applied to derive a recommended 90-day continuous exposure limit (CEL) of 0.8% for CO2 . As reproductive endpoints that are developmental in nature must be assumed to result from a single exposure at a critical point during gestation, it is further recommended that the 24-hr emergency exposure limit (EEL) also be 0.8%.

Twenty Thousand Needles Under the Sea. Trigger Point Dry Needling Aboard an Israeli Navy Submarine: A Case Report.

Nonspecific lower back pain affects a major part of the population at a certain point of their life. The intensity of pain can be debilitating and it causes a significant burden on society. Trigger point dry needling is a method of alleviating such pain by the introduction of needles into trigger points in muscles. A growing body of evidence supports its use in myofascial pain and specifically lower back pain. Submarine Medicine is a unique field due to the special characteristics and the environment of the submarine. It poses challenges that are not always seen by primary care physicians. Here, we present a case of a 40-yr-old senior submarine officer who complained of pain in his lower back and pelvis before departing on a mission. The pain persisted in spite of treatment with nonsteroidal anti-inflammatory drugs and he was then treated by the submarine's physician with trigger point dry needling. The officer showed rapid improvement following this treatment, both regarding pain and the range of motion.

Decompressing rescue personnel during Australian submarine rescue operations.

INTRODUCTION: Personnel rescuing survivors from a pressurized, distressed Royal Australian Navy (RAN) submarine may themselves accumulate a decompression obligation, which may exceed the bottom time limits of the Defense and Civil Institute of Environmental Medicine (DCIEM) Air and In-Water Oxygen Decompression tables (DCIEM Table 1 and 2) presently used by the RAN. This study compared DCIEM Table 2 with alternative decompression tables with longer bottom times: United States Navy XVALSS_DISSUB 7, VVAL-18M and Royal Navy 14 Modified tables. METHODS: Estimated probability of decompression sickness (PDCS), the units pulmonary oxygen toxicity dose (UPTD), the volume of oxygen required and the total decompression time were calculated for hypothetical single and repetitive exposures to 253 kPa air pressure for various bottom times and prescribed decompression schedules. RESULTS: Compared to DCIEM Table 2, XVALSS_DISSUB 7 single and repetitive schedules had lower estimated PDCS, which came at the cost of longer oxygen decompressions. For single exposures, DCIEM schedules had PDCS estimates ranging from 1.8% to 6.4% with 0 to 101 UPTD and XVALSS_DISSUB 7 schedules had PDCS of less than 3.1%, with 36 to 350 UPTD. CONCLUSIONS: The XVALSS_DISSUB 7 table was specifically designed for submarine rescue and, unlike DCIEM Table 2, has schedules for the estimated maximum required bottom times at 253 kPa. Adopting these tables may negate the requirement for saturation decompression of rescue personnel exceeding DCIEM limits.

Decompression illness in goats following simulated submarine escape: 1993-2006.

The United Kingdom Ministry of Defence commissioned work to define the relationship between the internal pressure of a distressed submarine (DISSUB), the depth from which escape is made and the risk of decompression illness (DCI). The program of work used an animal model (goat) to define these risks and this paper reports the incidence and type of DCI observed. A total of 748 pressure exposures comprising saturation only, escape only or saturation followed by escape were conducted in the submarine escape simulator between 1993 and 2006. The DCI following saturation exposures was predominantly limb pain, whereas following escape exposures the DCI predominantly involved the central nervous system and was fast in onset. There was no strong relationship between the risk of DCI and the range of escape depths investigated. The risk of DCI incurred from escape following saturation was greater than that obtained by combining the risks for the independent saturation only, and escape only, exposures. The output from this program of work has led to improved advice on the safety of submarine escape.

Submarine tower escape decompression sickness risk estimation.

Actions to enhance survival in a distressed submarine (DISSUB) scenario may be guided in part by knowledge of the likely risk of decompression sickness (DCS) should the crew attempt tower escape. A mathematical model for DCS risk estimation has been calibrated against DCS outcome data from 3,738 exposures of either men or goats to raised pressure. Body mass was used to scale DCS risk. The calibration data included more than 1,000 actual or simulated submarine escape exposures and no exposures with substantial staged decompression. Cases of pulmonary barotrauma were removed from the calibration data. The calibrated model was used to estimate the likelihood of DCS occurrence following submarine escape from the United Kingdom Royal Navy tower escape system. Where internal DISSUB pressure remains at - 0.1 MPa, escape from DISSUB depths < 200 meters is estimated to have DCS risk < 6%. Saturation at raised DISSUB pressure markedly increases risk, with > 60% DCS risk predicted for a 200-meter escape from saturation at 0.21 MPa. Using the calibrated model to predict DCS for direct ascent from saturation gives similar risk estimates to other published models.

Submarine 'safe to escape' studies in man.

The Royal Navy requires reliable advice on the safe limits of escape from a distressed submarine (DISSUB). Flooding in a DISSUB may cause a rise in ambient pressure, increasing the risk of decompression sickness (DCS) and decreasing the maximum depth from which it is safe to escape. The aim of this study was to investigate the pressure/depth limits to escape following saturation at raised ambient pressure. Exposure to saturation pressures up to 1.6 bar (a) (160 kPa) (n = 38); escapes from depths down to 120 meters of sea water (msw) (n = 254) and a combination of saturation followed by escape (n = 90) was carried out in the QinetiQ Submarine Escape Simulator, Alverstoke, United Kingdom. Doppler ultrasound monitoring was used to judge the severity of decompression stress. The trials confirmed the previously untested advice, in the Guardbook, that if a DISSUB was lying at a depth of 90 msw, then it was safe to escape when the pressure in the DISSUB was 1.5 bar (a), but also indicated that this advice may be overly conservative. This study demonstrated that the upper DISSUB saturation pressure limit to safe escape from 90 msw was 1.6 bar (a), resulting in two cases of DCS.

Initial review of the U.S. Navy's pressurized submarine escape training outcomes.

The U.S. Navy reinstituted pressurized submarine escape training (PSET) for submarine sailors in 2009 after a nearly 30-year absence. This training addresses escape from a disabled submarine at depth with the use of the Beaufort, Ltd. Mk 10 Submarine Escape and Immersion Equipment (SEIE) suit. Training is classified as "high-risk" due to previous U.S. and foreign navy experience with training-associated morbidity and mortality, particularly from diving-related illness. To reduce risk, medical screening procedures are performed. During the first 39 months of training, 7,025 students screened for PSET with 32% completing all phases, including two pressurized ascents. The most common reason for screening disqualification was presence of upper respiratory congestion. During training, middle ear barotrauma was responsible for 53% of attrition, primarily during the test of pressure.

Negative pressure breathing increases cardiac output and nitrogen elimination in seated subjects.

During denitrogenation for rescue, crew members of an internally pressurized disabled submarine (DISSUB) must sit upright, which may hamper venous return, cardiac output and peripheral circulation. Since negative pressure breathing (NPB) might counteract this problem, denitrogenation was measured in sitting subjects performing NPB. Seven male subjects completed 125-minute nitrogen (N2) washouts breathing either 100% oxygen (O2) or a normoxic gas (21% O2 in argon) in control conditions and intermittent (I: inspirations only) or continuous (C) NPB at -10 or -15 cmH2O. N2 elimination was measured using a closed rebreathing system. INPB (intermittent) (-15cmH2O) and CNPB (continous breathing) (-10 and -15cmH2O) increased cardiac output (CO) 9% during both O2 and normoxic breathing. Systolic and diastolic blood pressures were unaffected by the CO increase, suggesting a peripheral vasodilatation and enhanced tissue perfusion leading to increased N2 elimination. With the CO boost, N2 washout increased 6% breathing O2 at -15 cmH2O CNPB and INPB, while during normoxic breathing there were 6% and 12% increases due to CNBP, -10 and -15 respectively and 6% with -15cmH2O INPB; breathing 100% O2 yielding 5% to 15% less N2 washout than normoxic breathing. Negative pressure breathing during denitrogenation may facilitate decompression in divers and in crew members being rescued from a DISSUB.

Evaluating the effectiveness of the US Navy and Marine Corps Tobacco Policy: an assessment of secondhand smoke exposure in US Navy submariners.

OBJECTIVE: To evaluate the effectiveness of the US Navy and Marine Corps tobacco policy in protecting submariners from secondhand smoke (SHS) by determining if non-tobacco users experienced a significant increase in urinary cotinine levels at sea when compared with in port levels. METHODS: From February to August 2009, 634 volunteers recruited from nine US Navy submarines completed a survey to collect demographic data, information on tobacco use and pre-deployment exposure to SHS. Non-tobacco users (n=239) were requested to provide two urine samples (pre-deployment and while at sea) to quantify exposure to SHS using urinary cotinine as a biomarker. Matched samples were analysed using liquid chromatography-tandem mass spectrometry. RESULTS: Overall, deployed cotinine levels were 2.1 times the in port levels in non-tobacco using submariners (95% CI 1.8 to 2.4, p<0.001, n=197). A significant increase in deployed urinary cotinine levels was found aboard six of nine submarines (p<0.05). A subgroup of submariners (n=91) who reported no SHS exposure within 10 days prior to in port cotinine sampling had deployed cotinine levels 2.7 times the in port levels (95% CI 2.2 to 3.3, p<0.001). Applying a 4.5:1 urine cotinine to serum cotinine correction factor, submariners' deployed geometric means are similar to recent US male population values at the 75th percentile. CONCLUSIONS: This study provides evidence that non-tobacco using submariners were exposed to SHS. Exposure was seen in all submarine classes and was not limited to personnel working in proximity to the smoking area. The existing policy was inadequate to protect non-smokers from exposure to SHS and required revision. As a result of a policy review, informed by this study, smoking below decks was banned aboard all US Navy submarines effective 31 December 2010.

[Capabilities of telemedicine in conditions of self-contained shipping].

Was analyzed a capability of effectuating of telemedicine between a ship in automized navigation and specialists of board medical service using different variants of technical supporting and communication channels. During trial session of telemedicine was effectuated fibergastroduodenoscopy in operation room of cruiser, situated near a quay. Then session was effectuated when the ship was in sea. Was made a conclusion that effectuating sessions of telemedicine of physicians of board medical service and physicians of a ship in automized navigation is capable and advisable, but variants of technical realization need a development.

A comparison of thermal stress in the submarine escape using immersion half- and full suit in tropical weather operations.

OBJECTIVE: Submariners of disabled submarines are subject to drastic weather changes as they are awaiting rescue on the sea surface. Hyperthermia and hypothermia are just two of the adverse conditions that they can experience. The purpose of this study was to investigate the effectiveness of two models of submarine escape and the protective capabilities of immersion suits from environmental changes. METHOD: A randomized study involving 24 male subjects was conducted to compare the thermal capabilities of the full- versus half-configuration suit in a climate-controlled chamber. RESULTS: The full-configuration suits tested for a higher mean maximal core temperature (37.76 degrees C / 99.97 degrees F) than the mean maximal core temperature of the half-suits (37.52 degrees C / 99.54 degrees F). The full suits also tested for a higher mean minimal core temperature (36.13 degrees C / 97.03 degrees F) than the mean minimal core temperature (35.95 degrees C / 96.71 degrees F) of the half-suits. CONCLUSION: Results showed that the full-suit configuration did not induce clinically significant high levels of heat stress as compared to the half-suits, but instead provided better thermal protection against hypothermia than the half-suits.

Fire and ice: diagnosis of carbon monoxide poisoning in a remote environment.

Following an explosion on board a British Navy submarine operating under the Polar ice cap, a 33-year-old sailor fought a fire without protective breathing apparatus. He was found confused, with soot about his nares. A suspected diagnosis of carbon monoxide (CO) poisoning was rapidly confirmed on site using a new non-invasive pulse CO-oximeter. Initial carboxyhaemoglobin (COHb) level was 28%. He was treated with high-flow oxygen and evacuated to a medical facility with hyperbaric oxygen treatment capability. Fifteen other crew members potentially exposed to smoke in the enclosed space were screened in less than 10 min and had normal COHb levels of 1-2%. This is the first case demonstrating the utility of pulse CO oximetry for diagnosing CO poisoning in remote environments. The information obtained allowed immediate delivery of appropriate on-site treatment and directed subsequent triage. The device was also shown to be effective for the rapid screening of numerous individuals. Not only does it have the potential to provide information that would otherwise be unobtainable in such a situation, but it could play an important role in mass casualty screening.