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.

A Preliminary Description of the Health of Women Navy Divers: An Examination of Linked Medical, Personnel, and Dive Log Data for 47 Women Divers Who Separated Between 2008 and 2018.

INTRODUCTION: Although women have always served in the U.S. Armed Forces, it has only been in the last half century that systematic examinations have been done on the health issues experienced by military women. Still, little is known about how occupational health risks among Navy divers might vary between men and women. Our objective was to use available data to examine health issues among all separating divers and then determine how prevalence rates varied between men and women for diagnoses made within the diver's last year of active duty service. MATERIALS AND METHODS: For this retrospective observational study, medical records and personnel data were linked with dive logs at the individual level. We calculated sex-specific prevalence rates and relative risks per 1,000 divers by major diagnostic categories and by specific disease diagnoses. RESULTS: We identified 47 women among the 4,623 active duty Navy divers (1.0%) who separated between 2008 and 2018. Ages varied between 19 and 54 years (M = 33, SD = 8) for women, compared to men who were 18-65 years (M = 35, SD = 9). When compared to men, women had about six times the rate of diseases of the genitourinary system, twice the rate of respiratory system diseases, and about four times as many diagnoses of disorders of the lacrimal system. CONCLUSIONS: The findings of much higher relative risks for women for conditions such as genitourinary disease, skin conditions, and acute respiratory infections require follow-up research to look for causes and potential risk reduction interventions. Future research must determine specific and relative risks as a necessary precursor to developing, implementing, and testing potentially sex-specific risk reduction and health improvement interventions.

Prescription medication use and trends for U.S. Navy submariners from 2007 to 2018.

Introduction: This is the first study to examine population medication prescription rates among U.S. submariners by common therapeutic classifications. Methods: Individual-level pharmacy records during the years 2007 to 2018 were extracted from the Military Health System's Pharmacy Data Transaction Service (PDTS) file. Demographic and military factors captured from Navy personnel files were linked to PDTS records. Logistic regression models were used to identify characteristics and trends associated with prevalence. Published total rates for other active-duty components were compared to submariner rates. Results: There were data for 50,720 submariners, among whom 576,782 prescriptions were filled. Prevalence rates decreased significantly from 2007-2018 among most drug classes. Central nervous system agents accounted for 31% of the total prescriptions, followed by 12% for eye, ear, nose, and throat preparations, and 10% for anti-infective agents. Higher prescription rates were associated with being enlisted, younger, a woman, lower-ranked, or Hispanic. The mean yearly prescription rate was 2.7 per submariner, less than half of the overall rate of all military components. Conclusion: The survival benefit of HBO2 therapy observed in our unadjusted analysis suggests that there may be therapeutic benefits of HBO2 in treating COVID-19 hypoxia as an adjunct to standard care.

Health Conditions Among Navy Submariners at the End of Active Duty; A Retrospective Cohort Study.

INTRODUCTION: Maintaining healthy, well-trained, and highly qualified armed forces is critical for ensuring military readiness. The purpose of this article is to contribute to the body of research focused on the health of U.S. Navy submariners and to identify the health conditions of U.S. Navy submariners during their final year of active duty service. MATERIALS AND METHODS: In this retrospective cohort study, we examined medical records and personnel files of separating U.S. Navy sailors who were: (1) active duty between 2009 and 2018; (2) separated before 2019; and (3) were assigned to a submarine for at least 30 days. Both officers and enlisted service members were included. We linked, described, and analyzed data from the Defense Health Agency, Military Health System Data Repository (MDR), and the Bureau of Naval Personnel (BUPERS). International Classification of Diseases (ICD) diagnoses codes were obtained from MDR. Data collected from BUPERS include age, sex, and rank. We determined the number of individuals who had at least one diagnosed condition (identified as a three-digit ICD code). We report the number of diagnoses and calculate prevalence rates and confidence intervals per condition, as well as prevalence rates per year, using standard formulas. The study was approved by the Naval Submarine Medical Research Laboratory Institutional Review Board. RESULTS: During the study period, 26,014 submariners separated from the Navy. The average number of separations per year was 2,601. About a third of the separating submariners were in the 25 to 29 age group and over 50% were under 30 years of age. Of the three-digit individual ICD codes, some of the highest operationally relevant rates over the 10-year study period (2009-2018) were for joint disorders (prevalence rate [PR] = 180 per 1,000 submariners), back disorders (PR = 128), and sleep disorders (PR = 134). Three mental-health-related conditions were also among the 20 conditions with the highest rates. CONCLUSIONS: High rates of specific diagnoses such as joint disorders indicate the need for additional study to examine causal relationships, to determine which conditions may contribute to lost work time, early separations, or low rates of reenlistment and which conditions might be a result of specific military occupations or duties. Study strengths are the large number of subjects and the long period of observations. A study weakness was the inability to identify submariners who separated because of health conditions. The overall impact of the study is that it identifies urgent health risks and establishes a way to prioritize future research. Future research should include a focus on medically separated personnel; compare rates for submariners to other military groups including all-Navy and all-Department of Defense; and determine specific and relative risks as a necessary precursor to developing, implementing, and testing risk reduction and health improvement interventions.

Health conditions among Navy divers at end of service: a retrospective cohort study.

PURPOSE: To identify the most prevalent health conditions among divers during their last year of Navy service. METHODS: For this retrospective descriptive study we used data from the Dive Jump Reporting System to identify 4,623 active-duty divers who separated between 2008 and 2018. Medical records, dive histories, and personnel files were merged, linked and analyzed at the individual level. RESULTS: On average, 420 divers separated each year. Among the separating divers, 99% were male, 26% were aged 25 to 29 years old with a mean age of 35 (SD = 9, range 18 to 65). The major medical categories with the highest numbers of divers affected were: musculoskeletal system diseases (prevalence rate (PR) = 515.2 per 1,000 divers/year); nervous system (PR = 411.9); injury and poisonings (PR = 249.8); and mental disorders (PR = 237.3). Of the 50 specific conditions that affected the most divers the top four were joint disorders (PR = 34.5), disorders of refraction and accommodation (PR = 30.1), back disorders (PR = 26.8) and organic sleep disorders (PR = 21.6). Compared to divers with fewer than 29 dives, divers with 49-plus dives were about twice as likely to have diagnoses related to symptoms involving head and neck. CONCLUSIONS: The study found high rates of conditions such as musculoskeletal disorders, joint and back disorders, and some mental health related disorders. Special warfare divers have high rates of hearing loss, and other disorders of ear. The results show the need and to develop and implement group-specific mitigation programs.

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.

Comparison of Body Composition Assessed by Dual-Energy X-Ray Absorptiometry and BMI in Current and Former U.S. Navy Service Members.

BACKGROUND: Little is known of the diagnostic accuracy of BMI in classifying obesity in active duty military personnel and those that previously served. Thus, the primary objectives were to determine the relationship between lean and fat mass, and body fat percentage (BF%) with BMI, and assess the agreement between BMI and BF% in defining obesity. METHODS: Body composition was measured by dual-energy X-ray absorptiometry in 462 males (20-91 years old) who currently or previously served in the U.S. Navy. A BMI of ≥ 30 kg/m2 and a BF% ≥ 25% were used for obesity classification. RESULTS: The mean BMI (± SD) and BF% were 28.8 ± 4.1 and 28.9 ± 6.6%, respectively, with BF% increasing with age. Lean mass, fat mass, and BF% were significantly correlated with BMI for all age groups. The exact agreement of obesity defined by BMI and BF% was fair (61%), however, 38% were misclassified by a BMI cut-off of 30 when obesity was defined by BF%. CONCLUSIONS: From this data we determined that there is a good correlation between body composition and BMI, and fair agreement between BMI and BF% in classifying obesity in a group of current and former U.S. Navy service members. However, as observed in the general population, a significant proportion of individuals with excess fat are misclassified by BMI cutoffs.

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.

Detecting incipient inner-ear damage from impulse noise with otoacoustic emissions.

Audiometric thresholds and otoacoustic emissions (OAEs) were measured in 285 U.S. Marine Corps recruits before and three weeks after exposure to impulse-noise sources from weapons' fire and simulated artillery, and in 32 non-noise-exposed controls. At pre-test, audiometric thresholds for all ears were

Low-level otoacoustic emissions may predict susceptibility to noise-induced hearing loss.

In a longitudinal study with 338 volunteers, audiometric thresholds and otoacoustic emissions were measured before and after 6 months of noise exposure on an aircraft carrier. While the average amplitudes of the otoacoustic emissions decreased significantly, the average audiometric thresholds did not change. Furthermore, there were no significant correlations between changes in audiometric thresholds and changes in otoacoustic emissions. Changes in transient-evoked otoacoustic emissions and distortion-product otoacoustic emissions were moderately correlated. Eighteen ears acquired permanent audiometric threshold shifts. Only one-third of those ears showed significant otoacoustic emission shifts that mirrored their permanent threshold shifts. A Bayesian analysis indicated that permanent threshold shift status following a deployment was predicted by baseline low-level or absent otoacoustic emissions. The best predictor was transient-evoked otoacoustic emission amplitude in the 4-kHz half-octave frequency band, with risk increasing more than sixfold from approximately 3% to 20% as the emission amplitude decreased. It is possible that the otoacoustic emissions indicated noise-induced changes in the inner ear, undetected by audiometric tests. Otoacoustic emissions may therefore be a diagnostic predictor for noise-induced-hearing-loss risk.