Senior Aviator Medical Qualification Status

INTRODUCTION

Aviation personnel are expensive to train and challenging for the services to retain because of lucrative opportunities in the civilian aviation sector and a desire among pilots for agency. The military services' retention efforts have typically utilized a combination of high continuation pays and longer service commitments of up to 10 years following initial training. One area that the services have overlooked in their attempts to retain senior aviators is quantifying and reducing medical disqualifications. Much as aging aircraft require increasing maintenance to retain full operational capability, so may pilots and other aircrew members.

MATERIALS AND METHODS

This article reports on a prospectively collected cross-sectional research study evaluating the medical status of senior aviation personnel who reported being considered or selected for command. The study was deemed exempt from human subjects research by the Institutional Review Board and a waiver of Health Insurance Portability and Accountability Act was granted. The study, which collected data at the Pentagon Flight Medical Clinic over 1 year, used a chart review of routine medical encounters and flight physicals to collect descriptive data. The goals of the study were to establish the prevalence of medically disqualifying conditions, assess the association between disqualifying conditions and age, and generate hypotheses for further research. Logistic regression of waiver need was performed for variables including prior waivers, waiver count, service, platform, age, and gender. ANOVA of readiness percentages vs. DoD targets were assessed between the services individually and in aggregate.

RESULTS

The study demonstrated medical readiness rates among command-eligible senior aviators ranging from 74% for the Air Force to 40% for the Army with the Navy and Marine Corps in the middle. The sample was insufficiently powered to demonstrate differences in readiness between the services; however, the population as a whole was significantly below the DoD's readiness target of >90% (P = .000).

CONCLUSIONS

None of the services met the DoD minimum readiness target of 90%. Markedly higher readiness was observed in the Air Force, the only service with a medical screening incorporated into its command selection process, but this difference was not statistically significant. Waivers increased with age and musculoskeletal concerns were common. A larger prospective cohort study should be considered to further elucidate and confirm the findings of this study. If further research confirms these findings, consideration should be made of screening command applicants for medical readiness.

"Spaceflight-to-Eye Clinic": Terrestrial advances in ophthalmic healthcare delivery from space-based innovations

The phrase "Bench-to-Bedside" is a well-known phrase in medicine, highlighting scientific discoveries that directly translate to impacting patient care. Key examples of translational research include identification of key molecular targets in diseases and development of diagnostic laboratory tests for earlier disease detection. Bridging these scientific advances to the bedside/clinic has played a meaningful impact in numerous patient lives. The spaceflight environment poses a unique opportunity to also make this impact; the nature of harsh extraterrestrial conditions and medically austere and remote environments push for cutting-edge technology innovation. Many of these novel technologies built for the spaceflight environment also have numerous benefits for human health on Earth. In this manuscript, we focus on "Spaceflight-to-Eye Clinic" and discuss technologies built for the spaceflight environment that eventually helped to optimize ophthalmic health on Earth (e.g., LADAR for satellite docking now utilized in eye-tracking technology for LASIK). We also discuss current technology research for spaceflight associated neuro-ocular syndrome (SANS) that may also be applied to terrestrial ophthalmic health. Ultimately, various advances made to enable to the future of space exploration have also advanced the ophthalmic health of individuals on Earth.

Approaches to Medical Emergencies on Commercial Flights

In-flight medical incidents are becoming increasingly critical as passengers with diverse health profiles increase in the skies. In this paper, we reviewed how airlines, aviation authorities, and healthcare professionals respond to such emergencies. The analysis was focused on the strategies developed by the top ten airlines in the world by examining training in basic first aid, collaboration with ground-based medical support, and use of onboard medical equipment. Appropriate training of crew members, availability of adequate medical resources on board airplanes, and improved capabilities of dialogue between a flying plane and medical doctors on the ground will contribute to a positive outcome of the majority of medical issues on board airlines. In this respect, the adoption of advanced telemedicine solutions and the improvement of real-time teleconsultations between aircraft and ground-based professionals can represent the future of aviation medicine, offering more safety and peace of mind to passengers in case of medical problems during a flight.

Space Ultrasound: A Proposal for Competency-based Ultrasound Training for In-flight Space Medicine

Space travel has transformed in the past several years. Given the burgeoning market for space tourism, in-flight medical emergencies are likely to be expected. Ultrasound is one of the few diagnostic and therapeutic modalities available for astronauts in space. However, while point-of-care ultrasound (POCUS) is available, there is no current standard of training for astronaut preparation. We suggest an organized and structured methodology by which astronauts should best prepare for space with the medical equipment available on board. As technology continues to evolve, the assistance of other artificial intelligence and augmented reality systems are likely to facilitate training and dynamic real-time needs during space emergencies. Summary: As space tourism continues to evolve, an organized methodology for POCUS use is advised to best prepare astronauts for space.

Coronary Artery Disease Management in Military Aircrew

INTRODUCTION: Coronary artery disease (CAD) is the leading cause of denial or withdrawal of flying privileges for aircrew. Screening for CAD is therefore crucial. The present study analyzed German military aircrew with diagnosed CAD and/or acute coronary syndrome despite close medical monitoring with the intention to further optimize individual outcomes and aeromedical disposition.METHODS: The digital information systems of the German Air Force Centre of Aerospace Medicine were searched for pilots and nonpilot aircrew with CAD and/or myocardial infarction (MI). They were retrospectively analyzed for age at initial diagnosis, body mass index, cardiovascular risk factors, diagnostic procedures, treatment, and aeromedical disposition.RESULTS: Between February 1987 and March 2023, 126 aircrew, 55% pilots and 45% nonpilot aircrew, were identified with CAD and/or MI. An accumulation of two to six risk factors was found in 77% of both groups. Most pilots (54%) received conservative treatment, 44% underwent percutaneous coronary intervention, and 3% coronary artery bypass grafting. In the group of nonpilot aircrew, conservative treatment was performed in 47%, coronary intervention in 37%, and bypass grafting in 16%. A total of 45 pilots (65%) returned to flying duties, albeit 39 (57%) with restrictions. In the group of nonpilot aircrew, 31 (54%) returned to flying duties.DISCUSSION: A small group of aircrew developed CAD over the years, some with severe coronary artery stenoses and MI. Further optimization of individual prognosis and aeromedical disposition should aim at appropriate CAD screening and risk factor elimination. CAD management needs a comprehensive approach regarding military aviation requirements and clinical guidance.Guettler N, Sammito S. Coronary artery disease management in military aircrew. Aerosp Med Hum Perform. 2023; 94(12):917-922.

Radiation protection and estimate of commercial aircrew effective doses in Bosnia and Herzegovina

Cosmic rays are the primary source of the daily exposure of aircrew and passengers to ionising radiation. This study aims to estimate the effective doses of ionising radiation for aircraft crews in Bosnia and Herzegovina by taking into consideration factors such as flight duration and altitude, as well as the geographical position of airports. The CARI-7 algorithm and neural network method were used in the analysis of data obtained from the Sarajevo International Airport. The results show that the estimated annual effective doses in 2021 range from 0.06 to 10 mSv for flights to and from Belgrade and Dubai, respectively. Both linear regression and neural network models were developed to predict the effective dose based on flight duration, average altitude, latitude and maximum altitude. The findings reveal that flight duration is the most statistically significant factor, followed by average altitude, latitude and maximum altitude.

Crew Autonomy During Simulated Medical Event Management on Long Duration Space Exploration Missions

OBJECTIVE

Our primary aim was to investigate crew performance during medical emergencies with and without ground-support from a flight surgeon located at mission control.

BACKGROUND

There are gaps in knowledge regarding the potential for unanticipated in-flight medical events to affect crew health and capacity, and potentially compromise mission success. Additionally, ground support may be impaired or periodically absent during long duration missions.

METHOD

We reviewed video recordings of 16 three-person flight crews each managing four unique medical events in a fully immersive spacecraft simulator. Crews were randomized to two conditions: with and without telemedical flight surgeon (FS) support. We assessed differences in technical performance, behavioral skills, and cognitive load between groups.

RESULTS

Crews with FS support performed better clinically, were rated higher on technical skills, and completed more clinical tasks from the medical checklists than crews without FS support. Crews with FS support also had better behavioral/non-technical skills (information exchange) and reported significantly lower cognitive demand during the medical event scenarios on the NASA-TLX scale, particularly in mental demand and temporal demand. There was no significant difference between groups in time to treat or in objective measures of cognitive demand derived from heart rate variability and electroencephalography.

CONCLUSION

Medical checklists are necessary but not sufficient to support high levels of autonomous crew performance in the absence of real-time flight surgeon support.

APPLICATION

Potential applications of this research include developing ground-based and in-flight training countermeasures; informing policy regarding autonomous spaceflight, and design of autonomous clinical decision support systems.

In-flight Medical Emergencies

In 2018, approximately 2.8 million passengers flew in and out of U.S. airports per day. Twenty-four to 130 in-flight medical emergencies are estimated to occur per 1 million passengers; however, there is no internationally agreed-upon recording or classification system. Up to 70% of in-flight emergencies are managed by the cabin crew without additional assistance. If a health care volunteer is requested, medical professionals should consider if they are in an appropriate condition to render aid, and then identify themselves to cabin crew, perform a history and physical examination, and inform the cabin crew of clinical impressions and recommendations. An aircraft in flight is a physically constrained and resource-limited environment. When needed, an emergency medical kit and automated external defibrillator are available on all U.S. aircraft with at least one flight attendant and a capacity for 30 or more passengers. Coordinated communication with the pilot, any available ground-based medical resources, and flight dispatch is needed if aircraft diversion is recommended. In the United States, medical volunteers are generally protected by the Aviation Medical Assistance Act of 1998. There is no equivalent law governing international travel, and legal jurisdiction depends on the patient's and medical professional's countries of citizenship and the country in which the aircraft is registered.

Assessing Patients for Air Travel

Advising patients before air travel is a frequently overlooked, but important, role of the physician, particularly primary care providers and pulmonary specialists. Although physiologic changes occur in all individuals during air travel, those with underlying pulmonary disease are at increased risk of serious complications and require a specific approach to risk stratification. We discuss the available tools for assessment of preflight risk and strategies to minimize potential harm. We also present a case discussion to illustrate our approach to assessing patients for air travel and discuss the specific conditions that should prompt a more thorough preflight workup.

A methodology for investigating the impact of medical countermeasures on the risk of exposure induced death

The space radiation environment is composed of ionizing particles that may pose health risks to crew members during Low Earth Orbit (LEO) and deep space missions. NASA has established astronaut career radiation limits for cancer of 3% Risk of Exposure Induced Death (REID) at the 95% confidence level. The REID is the increased lifetime risk of death from cancer due to radiation exposure in comparison to an unexposed background population and has been traditionally mitigated by passive shielding design concepts and limiting safe days in space. Additional reduction in radiation exposure risk may be achieved with Medical Countermeasures (MCM). Recent meta-analyses have demonstrated the efficacy of aspirin in the reduction of the background colorectal cancer incidence and mortality rates for specific cohorts. Additional studies of warfarin in patients greater than 50 years of age have indicated statistically significant decreases in stomach, bladder, brain, prostate, and lung cancer incidence as compared to control groups. While ultimate selection of suitable countermeasures will be the responsibility of flight surgeons, this paper presents a general methodology for incorporating MCM into the NASA Space Radiation Cancer Risk model and includes modifications of the background mortality rates (hazard rates) and the radiation risk coefficients to numerically quantify the benefits of MCM. As examples of the method, aspirin and warfarin will be employed as MCM in a sensitivity analysis to compute the REID for astronauts embarking on a one-year deep space mission scenario.

Designing clinical trials for future space missions as a pathway to changing how clinical trials are conducted on Earth

OBJECTIVE

The project aims to build a framework for conducting clinical trials for long-term interplanetary missions to contribute to innovation in clinical trials on Earth, especially around patient involvement and ownership.

METHODS

We conducted two workshops in which participants were immersed in the speculative scenario of an interplanetary mission in which health problems emerged that required medical trials to resolve. The workshops used virtual reality and live simulation to mimic a zero-gravity environment and visual perception shifts and were followed by group discussion.

RESULTS

Some key aspects for the framework that emerged from the workshops included: (a) approaches to be inclusive in the management of the trial, (b) approaches to be inclusive in designing the research project (patient preference trials, n-of-1 trials, designing clinical trials to be part of a future prospective meta-analysis, etc), (c) balancing the research needs and the community needs (eg, allocation of the participants based on both research and community need), (d) ethics and partnerships (ethics and consent issues and how they relate to partnerships and relationships).

CONCLUSION

In identifying some key areas that need to be incorporated in future planning of clinical trials for interplanetary missions, we also identified areas that are relevant to engaging patients in clinical trials on Earth. We will suggest using the same methodology to facilitate more in-depth discussions on specific aspects of clinical trials in aerospace medicine. The methodology can be more widely used in other areas to open new inclusive conversations around innovating research methodology.

OVERVIEW OF AIRCREW EXPOSURE TO COSMIC RADIATION IN THE CZECH REPUBLIC

Monitoring of exposures of aircrew members of airline operators registered in the Czech Republic has been performed since 1998. The individual effective doses are calculated using the computer code CARI annually. The calculations are based on information about participation of aircrew members on the specific flights and on the parameters describing the typical flight profiles of the flights; the latter is regularly verified with control measurements performed onboard aircraft. The results show that (1) the average annual effective doses in the period from 1998 to 2017 range from 1.3 to 2.1 mSv, (2) the maximum effective dose of a crew member is 5.7 mSv and (3) the annual collective effective doses range from 1.3 to 4.1 manSv. Combined relative uncertainty of the results is ~25%.

Navigating the Management of an F-16 Pilot Following Spontaneous Splenic Rupture

BACKGROUND: Little consensus exists on the best practices for post-acute care of patients who suffer splenic injury but retain functional splenic tissue. Moreover, no published guidance or case reports exist for managing pilots in this demographic, making the flight surgeon's task particularly difficulty as he/she attempts to apply the best available evidence for a patient population exposed to unique occupational hazards.CASE REPORT: We describe the case of an F-16 pilot who suffered a spontaneous splenic rupture due to infectious mononucleosis and required splenic artery embolization for hemodynamic stabilization. Despite the salvage of a significant portion of his spleen, the pilot was managed as an asplenic patient due to concern that: 1) splenic artery embolization compromised the function of his spleen; and 2) his status as a military aviator placed him at increased risk of infection due to frequent travel. He received appropriate vaccinations for an asplenic patient, fever precautions, and amoxicillin-clavulanic acid for immediate use if he developed fever. After discussion with the Aeromedical Consult Service, who felt the aviator had minimal risk of a poor outcome, he was returned to flying status. Since returning to flying status he has logged over 15 h of flight time, routinely experiencing 8-9 +G_z without difficulty.DISCUSSION: This case provides a successful approach to the management of pilots of high-performance aircraft who suffer splenic injury but retain functional splenic tissue, and provides precedent for safely returning these patients to flying status following recovery.Tanael M, Saul S. Navigating the management of an F-16 pilot following spontaneous splenic rupture. Aerosp Med Hum Perform. 2019; 90(12):1061-1063.

Assessment of Jugular Venous Blood Flow Stasis and Thrombosis During Spaceflight

IMPORTANCE

Exposure to a weightless environment during spaceflight results in a chronic headward blood and tissue fluid shift compared with the upright posture on Earth, with unknown consequences to cerebral venous outflow.

OBJECTIVES

To assess internal jugular vein (IJV) flow and morphology during spaceflight and to investigate if lower body negative pressure is associated with reversing the headward fluid shift experienced during spaceflight.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study included 11 International Space Station crew members participating in long-duration spaceflight missions . Internal jugular vein measurements from before launch and approximately 40 days after landing were acquired in 3 positions: seated, supine, and 15° head-down tilt. In-flight IJV measurements were acquired at approximately 50 days and 150 days into spaceflight during normal spaceflight conditions as well as during use of lower body negative pressure. Data were analyzed in June 2019.

EXPOSURES

Posture changes on Earth, spaceflight, and lower body negative pressure.

MAIN OUTCOMES AND MEASURES

Ultrasonographic assessments of IJV cross-sectional area, pressure, blood flow, and thrombus formation.

RESULTS

The 11 healthy crew members included in the study (mean [SD] age, 46.9 [6.3] years, 9 [82%] men) spent a mean (SD) of 210 (76) days in space. Mean IJV area increased from 9.8 (95% CI, -1.2 to 20.7) mm2 in the preflight seated position to 70.3 (95% CI, 59.3-81.2) mm2 during spaceflight (P < .001). Mean IJV pressure increased from the preflight seated position measurement of 5.1 (95% CI, 2.5-7.8) mm Hg to 21.1 (95% CI, 18.5-23.7) mm Hg during spaceflight (P < .001). Furthermore, stagnant or reverse flow in the IJV was observed in 6 crew members (55%) on approximate flight day 50. Notably, 1 crew member was found to have an occlusive IJV thrombus, and a potential partial IJV thrombus was identified in another crew member retrospectively. Lower body negative pressure was associated with improved blood flow in 10 of 17 sessions (59%) during spaceflight.

CONCLUSIONS AND RELEVANCE

This cohort study found stagnant and retrograde blood flow associated with spaceflight in the IJVs of astronauts and IJV thrombosis in at least 1 astronaut, a newly discovered risk associated with spaceflight. Lower body negative pressure may be a promising countermeasure to enhance venous blood flow in the upper body during spaceflight.

Integration of a Vestibular Model for the Disorientation Research Device Motion Algorithm Application

INTRODUCTION: Spatial disorientation (SD) remains a leading cause of Class A mishaps and fatalities in aviation. Motion-based flight simulators and other research devices provide the capacity to rigorously study SD in order to develop effective countermeasures. By applying mathematical models of human orientation perception, we propose an approach to improve control algorithms for motion-based flight simulators to study SD.METHODS: The Disorientation Research Device (DRD), or the Kraken™, is the Department of Defense's newest and most capable aerospace medicine motion-based research device. We implemented an "Observer" model for predicting aircrew spatial orientation perception within the DRD, and perceptions experienced in flight. Further, we propose a framework that uses the model output, in addition to pilot control inputs, to optimize multiaxis motion control including human-in-the-loop control capability.RESULTS: A case study was performed to demonstrate the functionality of the framework. Additionally, the case study highlights both how limitations of human perception are crucial to consider when designing motion algorithms, and the challenges of effective flight simulation with multiple motion axes.DISCUSSION: We implemented a mathematical model for spatial orientation perception to improve the design of control algorithms for motion-based flight simulators, using the DRD as an example application. We provide an example of predicting perceptions, producing quantitative information on the efficacy of motion control algorithms. This mathematical model based approach to validating motion control algorithms aims to improve the fidelity of ground-based SD research.Dixon JB, Etgan CA, Horning DS, Clark TK, Folga RV. Integration of a vestibular model for the Disorientation Research Device motion algorithm application. Aerosp Med Hum Perform. 2019; 90(10):901-907.

Assisting with air travel medical emergencies: responsibilities and pitfalls

When medical emergencies arise in flight, commercial airline flight crews may ask for help from onboard medical professionals. Qualified, active, licensed, and sober providers should volunteer to assist in the event of a medical emergency rather than decline out of fear of medicolegal reprisal. An understanding of the typically available resources, the hierarchy of authority, and medicolegal precedents can help providers feel confident in responding to these situations. This review addresses the pathophysiology related to air travel and common causes of in-flight medical emergencies and discusses the medications and equipment commonly stocked by commercial airlines. In addition, the complexity of flight diversion and the medicolegal concerns surrounding volunteering to provide medical care are addressed.

Aircrew Conditioning Programme Impact on +Gz Tolerance

INTRODUCTION: Physical conditioning may improve aircrew performance during exposure to high +G_z acceleration, although few studies have directly assessed this. The present study investigated the effects of a 12-wk Aircrew Conditioning Programme (ACP) on markers of G tolerance. The ACP comprises aerobic and muscle strengthening exercise performed twice weekly and targets improved fitness and reduced injury risk.METHODS: There were 36 UK Royal Air Force and Royal Navy aircrew who volunteered; 17 performed the ACP (Ex) and 19 acted as a control group (Con). Centrifuge testing was performed before and after the intervention. Relaxed G tolerance (RGT) and straining G tolerance (SGT), which had the addition of muscle tensing, were assessed. G endurance was also determined via repeated simulated air combat maneuvers (SACMs). During these centrifuge runs a number of physiological variables were recorded.RESULTS: During the G profile to determine RGT, neither RGT, HR, nor blood pressure responses were affected by the ACP. During SGT profiles, a lower HR at a given +G_z (+5.5 G_z) level following the ACP was observed (Ex: pre 146.0 ± 4.4, post 136.9 ± 5.6 bpm; Con: pre 148.0 ± 3.2, post 153.1 ± 3.3 bpm). BP was maintained and there was a tendency toward an improved SGT. The ACP increased the proportion of individuals completing the number of SACM profiles, although no meaningful differences were found between groups in other variables.CONCLUSION: Overall the ACP has no negative effect on RGT, reduced the physiological strain associated with a given level of +G_z (during SGT), and tended to improve the ability to tolerate repeated G_z exposure.Slungaard E, Pollock RD, Stevenson AT, Green NDC, Newham DJ, Harridge SDR. Aircrew conditioning programme impact on +Gz tolerance. Aerosp Med Hum Perform. 2019; 90(9):764-773.

Continuous Glucose Monitoring for In-Flight Measurement of Glucose Levels of Insulin-Treated Pilots

INTRODUCTION: Due to the risk of hypoglycemia-related incapacitation, diabetic pilots requiring insulin are assessed as unfit according to the International Civil Aviation Organization and most national authorities. Some authorities, such as those from Canada, the United Kingdom, and the United States, permit selected insulin-treated pilots (ITDM-pilots) to fly subject to a protocol requiring pre- and in-flight capillary glucose measurements to show safe levels (>100-<300 mg · dl^-1). Critics of such permission question the practicability of these in-flight measurements and whether clinically desired glycemic targets can be achieved while keeping glucose levels in the safe range. Subcutaneous continuous glucose monitoring (CGM) has recently been approved by the FDA as a stand-alone method to provide accurate glucose levels and treatment decision guidance in patients. This commentary considers that use of CGM by ITDM pilots facilitates practicability and recording of in-flight glucose measurements and facilitates achievement of clinically desired glycemic targets without increasing hypoglycemia risks.Strollo F, Simons R, Mambro A, Strollo G, Gentile S. Continuous glucose monitoring for in-flight measurement of glucose levels of insulin-treated pilots. Aerosp Med Hum Perform. 2019; 90(8):735-737.

Predicting Workload Experienced in a Flight Test by Measuring Workload in a Flight Simulator

BACKGROUND: In order to determine the minimum flight crew number and show compliance with airworthiness regulations, the workload of flight crew should be measured in various flight scenarios both in a simulator and in flight tests demonstrating compliance. However, the complexity, environment, and safety considerations of flight tests require pilots to take more responsibility and be more careful with decisions and actions with higher stress, and it might be inappropriate to carry out flight tests in a high-risk abnormal situation. Therefore, it is necessary to assess workload measures in a simulator to predict workload experienced during a flight test.METHODS: Two subjective workload measurements and three psychophysiological measurements were compared both in a simulator and in a flight test among three flight scenarios. The scenarios were carried out in an ARJ21-700 full-flight simulator and a corresponding aircraft, and a total of 17 pilots participated.RESULTS: Both flight scenarios and flight environment had a significant influence on NASA-TLX, eye blink rate, and heart rate. Additionally, the NASA-TLX (R = 0.864) and heart rate differences (R = 0.840) presented strong correlations between the simulator and flight test.DISCUSSION: NASA-TLX and heart rate could be used in simulators and flight tests as consistent measures of workload. Furthermore, in order to reduce the quantity and risk of compliance during a flight test, the best strategy is to combine the results of the NASA-TLX scales and HR-D together in a flight simulator to predict workload experienced in a flight test.Zheng Y, Lu Y, Jie Y, Fu S. Predicting workload experienced in a flight test by measuring workload in a flight simulator. Aerosp Med Hum Perform. 2019; 90(7):618-623.

High Altitude Performance of Loudspeakers and Potential Impact on Audiometric Findings

BACKGROUND: The evaluation of how air rarefaction can affect a loudspeaker performance at altitude implies the need for characterization of earphones during hypobaric conditions. The aim of this study was phonometric analysis at different altitudes of the acoustic output of a widely used earphone model, along with its consequences on audiological investigations conducted under such environmental conditions.METHODS: The transfer function of a TDH-39P earphone was analyzed with an artificial ear under nine different altitude levels, from sea level up to 35,000 ft, inside a hypobaric chamber. A specific phonometric system not sensitive to environmental pressure changes was used. Other potentially confounding factors, such as environmental temperature and humidity, were continuously monitored.RESULTS: No relevant temperature or humidity changes were detected. The sound pressure level generated by the earphone under hypobaric conditions was found considerably affected by air density changes. These data produced a correction table aiming at recalibrating the earphone's output at each audiometric octave test frequency within the 250-8000 Hz range. Quite different characteristics of response were observed at different audiometric frequencies. Such findings were particularly evident for altitudes exceeding 12,000 ft.DISCUSSION: The development of a frequency-selective and altitude-related correction factor for acoustic stimuli is an essential aspect when hearing threshold measurements in hypobaric environments are performed.Lucertini M, Botti T, Sanjust F, Cerini L, Autore A, Lucertini L, Sisto R. High altitude performance of loudspeakers and potential impact on audiometric findings. Aerosp Med Hum Perform. 2019; 90(7):655-659.

Modafinil as a Stimulant for Military Aviators

INTRODUCTION: Modafinil is a wakefulness-promoting stimulant that has been approved by the Republic of Singapore Air Force (RSAF) as a fatigue countermeasure medication since 2011. Each RSAF aircrew member must undergo a ground test to exclude operationally relevant adverse drug effects prior to consuming the medication for operational reasons. This study describes the RSAF's modafinil ground testing outcomes over a 7-yr period.METHODS: This is a retrospective case series of 243 RSAF aircrew members who underwent modafinil 100-mg test dosing over the 7-yr period from September 2011 to September 2018.RESULTS: The median age was 31 yr (range, 21-53 yr) and mean age was 31.7 yr ± 6.19 yr. Of the aircrew members, 234 (96.3%) were men and all were of Asian ethnicity. Of the subjects, 237 (97.5%) were medically cleared for the operational use of modafinil. Among the six (2.47%) who failed modafinil ground testing, headache (cumulative incidence, 1.65%), anxiety (cumulative incidence, 0.41%), diarrhea (cumulative incidence, 0.41%), and insomnia (cumulative incidence, 0.41%) were reported as the side effects experienced. None of the aircrew members experienced major adverse drug events.DISCUSSION: Our findings suggest a low occurrence of adverse drug effects among military aircrew members who undergo modafinil test dosing prior to using the drug operationally. To our knowledge, this is the single largest published case series of modafinil ground testing outcomes among Asian military aviators.Ooi T, Wong SH, See B. Modafinil as a stimulant for military aviators. Aerosp Med Hum Perform. 2019; 90(5):480-483.

Breath/Blood Alcohol Concentration as an Indicator of Alcohol Use Problems

INTRODUCTION: The Federal Aviation Administration Office of Aerospace Medicine (AAM) is required by law to identify pilots who have driving under the influence (DUI) convictions. It is the responsibility of AAM to determine, based on the DUI, if the pilot has a drinking problem and needs follow-up treatment. Pilots with alcohol problems are at risk to themselves and the public and need to have treatment to reduce the extent of the risk. It has been suggested by some that a blood alcohol concentration (BAC) of 0.15 g · dL^-1 is evidence of tolerance and the pilot should be placed in an alcohol treatment program.METHOD: The National Institute on Alcohol Abuse and Alcoholism (NIAAA) Clinician's Guide considers a person at risk for a drinking problem when a man drinks 5 or more drinks or a woman drinks 4 or more drinks in a day and reaches a 0.08 g · dL^-1 of ethanol in the blood. It is possible to estimate from a BAC or breath alcohol concentration (BrAC) the number of drinks consumed using the volume of distribution for ethanol and the weight of the individual. A spread sheet tool was developed to estimate the number of drinks consumed.RESULTS: It was determined that DUI/DWI concentrations could be used to determine the minimum number of drinks consumed. Overweight people reach binge drinking levels and higher Hingson levels at lower DUI/DWI concentrations than people with an average weight or lower.DISCUSSION: Using this tool there is a high probability (99.7%) of identifying a true binge drinker.Canfield DV, Forster EM, Cheong Z-I, Cowan JM. Breath/blood alcohol concentration as an indicator of alcohol use problems. Aerosp Med Hum Perform. 2019; 90(5):488-491.

Non-coronary cardiac surgery and percutaneous cardiology procedures in aircrew

This manuscript focuses on the broad aviation medicine considerations that are required to optimally manage aircrew following non-coronary surgery or percutaneous cardiology interventions (both pilots and non-pilot aviation professionals). Aircrew may have pathology identified earlier than non-aircrew due to occupational cardiovascular screening and while aircrew should be treated using international guidelines, if several interventional approaches exist, surgeons/interventional cardiologists should consider which alternative is most appropriate for the aircrew role being undertaken; liaison with the aircrew medical examiner is strongly recommended prior to intervention to fully understand this. This is especially important in aircrew of high-performance aircraft or in aircrew who undertake aerobatics. Many postoperative aircrew can return to restricted flying duties, although aircrew should normally not return to flying for a minimum period of 6 months to allow for appropriate postoperative recuperation and assessment of cardiac function and electrophysiology.

Congenital heart disease in aircrew

This article focuses i on the broad aviation medicine considerations that are required to optimally manage aircrew ii with suspected or confirmed congenital heart disease (both pilots and non-pilot aviation professionals). It presents expert consensus opinion and associated recommendations and is part of a series of expert consensus documents covering all aspects of aviation cardiology. This expert opinion was born out of a 3 year collaborative working group between international military aviation cardiologists and aviation medicine specialists, as part of a North Atlantic Treaty Organization (NATO) led initiative to address the occupational ramifications of cardiovascular disease in aircrew (HFM-251) many of whom also work with and advise civil aviation authorities.

The challenge of asymptomatic coronary artery disease in aircrew; detecting plaque before the accident

Coronary events remain a major cause of sudden incapacitation, including death, in both the general population and among aviation personnel, and are an ongoing threat to flight safety and operations. The presentation is often unheralded, especially in younger adults, and is often due to rupture of a previously non-obstructive coronary atheromatous plaque. The challenge for aeromedical practitioners is to identify individuals at increased risk for such events. This paper presents the NATO Cardiology Working Group (HFM 251) consensus approach for screening and investigation of aircrew for asymptomatic coronary disease.A three-phased approach to coronary artery disease (CAD) risk assessment is recommended, beginning with initial risk-stratification using a population-appropriate risk calculator and resting ECG. For aircrew identified as being at increased risk, enhanced screening is recommended by means of Coronary Artery Calcium Score alone or combined with a CT coronary angiography investigation. Additional screening may include exercise testing, and vascular ultrasound imaging. Aircrew identified as being at high risk based on enhanced screening require secondary investigations, which may include functional ischaemia, and potentially invasive coronary angiography. Functional stress testing as a stand-alone investigation for significant CAD is not recommended in aircrew. Aircrew identified with coronary disease require further clinical and aeromedical evaluation before being reconsidered for flying status.

Contemporaneous management of valvular heart disease and aortopathy in aircrew

Valvular heart disease (VHD) is highly relevant in the aircrew population as it may limit appropriate augmentation of cardiac output in high-performance flying and predispose to arrhythmia. Aircrew with VHD require careful long-term follow-up to ensure that they can fly if it is safe and appropriate for them to do so. Anything greater than mild stenotic valve disease and/or moderate or greater regurgitation is usually associated with flight restrictions. Associated features of arrhythmia, systolic dysfunction, thromboembolism and chamber dilatation indicate additional risk and will usually require more stringent restrictions. The use of appropriate cardiac imaging, along with routine ambulatory cardiac monitoring, is mandatory in aircrew with VHD.Aortopathy in aircrew may be found in isolation or, more commonly, associated with bicuspid aortic valve disease. Progression rates are unpredictable, but as the diameter of the vessel increases, the associated risk of dissection also increases. Restrictions on aircrew duties, particularly in the context of high-performance or solo flying, are usually required in those with progressive dilation of the aorta.

Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial

OBJECTIVE

To determine if using a parachute prevents death or major traumatic injury when jumping from an aircraft.

DESIGN

Randomized controlled trial.

SETTING

Private or commercial aircraft between September 2017 and August 2018.

PARTICIPANTS

92 aircraft passengers aged 18 and over were screened for participation. 23 agreed to be enrolled and were randomized.

INTERVENTION

Jumping from an aircraft (airplane or helicopter) with a parachute versus an empty backpack (unblinded).

MAIN OUTCOME MEASURES

Composite of death or major traumatic injury (defined by an Injury Severity Score over 15) upon impact with the ground measured immediately after landing.

RESULTS

Parachute use did not significantly reduce death or major injury (0% for parachute v 0% for control; P>0.9). This finding was consistent across multiple subgroups. Compared with individuals screened but not enrolled, participants included in the study were on aircraft at significantly lower altitude (mean of 0.6 m for participants v mean of 9146 m for non-participants; P<0.001) and lower velocity (mean of 0 km/h v mean of 800 km/h; P<0.001).

CONCLUSIONS

Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention. However, the trial was only able to enroll participants on small stationary aircraft on the ground, suggesting cautious extrapolation to high altitude jumps. When beliefs regarding the effectiveness of an intervention exist in the community, randomized trials might selectively enroll individuals with a lower perceived likelihood of benefit, thus diminishing the applicability of the results to clinical practice.

Remote Echography between a Ground Control Center and the International Space Station Using a Tele-operated Echograph with Motorized Probe

Echography is the most appropriate imaging modality for investigating astronauts. Unfortunately, it requires a great deal of training to perform ultrasound examinations, which can be difficult and time consuming, especially if the astronaut does not have a medical background. We designed a new echography system with motorized probes that allows for the majority of exam functions to be controlled by a ground-based sonographer. Using tele-operation, the sonographer controls the orientation of the transducer (tilt, rotation) and echograph settings (gain, depth, freeze) and triggers ultrasound functions (pulsed wave color Doppler, 3-D capture, radiofrequency data collection, elastography). With this system, astronauts are required to hold the motorized probe only at the locations indicated, with the remainder of the exam being conducted by the ground-based sonographer. During spaceflight, ultrasound imaging of the carotid artery, jugular vein, thyroid, liver, gallbladder, biliary tract and portal vein (2-D, 3-D, color, pulsed wave, radiofrequency) were successfully performed.

Fitness to fly in the paediatric population, how to assess and advice

The number of children on commercial aircrafts is rising steeply and poses a need for their treating physicians to be aware of the physiologic effects and risks of air travel. The most important risk factors while flying are a decrease in partial oxygen pressure, expansion of trapped air volume, low cabin humidity, immobility, recirculation of air and limited options for medical emergencies. Because on-board medical emergencies mostly concern exacerbations of chronic disease, the medical history, stability of current disease and previous flight experience should be assessed before flight. If necessary, hypoxia altitude simulation testing can be performed to simulate the effects of in-flight hypoxia. Although the literature on paediatric safety of air travel is sparse, recommendations for many different situations can be given.

CONCLUSION

We present an overview of the most up to date recommendations to ensure the safety of children during flight. What is Known: • Around 65% of on-board medical emergencies are complications of underlying disease. • In children, the three most common emergencies during flight concern respiratory, neurological and infectious disease. What is New: • Although studies are scarce, some advices to ensure safe air travel can be given for most underlying medical conditions in children, based on physiology, studies in adults and expert opinions. • In former preterm infants without chronic lung disease, hypoxia altitude simulation testing to rule out in-flight desaturation is not recommended.

Survey of Casualty Evacuation Missions Conducted by the 160th Special Operations Aviation Regiment During the Afghanistan Conflict

BACKGROUND

Historically, documentation of prehospital combat casualty care has been relatively nonexistent. Without documentation, performance improvement of prehospital care and evacuation through data collection, consolidation, and scientific analyses cannot be adequately accomplished. During recent conflicts, prehospital documentation has received increased attention for point-of-injury care as well as for care provided en route on medical evacuation platforms. However, documentation on casualty evacuation (CASEVAC) platforms is still lacking. Thus, a CASEVAC dataset was developed and maintained by the 160th Special Operations Aviation Regiment (SOAR), a nonmedical, rotary-wing aviation unit, to evaluate and review CASEVAC missions conducted by their organization.

METHODS

A retrospective review and descriptive analysis were performed on data from all documented CASEVAC missions conducted in Afghanistan by the 160th SOAR from January 2008 to May 2015. Documentation of care was originally performed in a narrative after-action review (AAR) format. Unclassified, nonpersonally identifiable data were extracted and transferred from these AARs into a database for detailed analysis. Data points included demographics, flight time, provider number and type, injury and outcome details, and medical interventions provided by ground forces and CASEVAC personnel.

RESULTS

There were 227 patients transported during 129 CASEVAC missions conducted by the 160th SOAR. Three patients had unavailable data, four had unknown injuries or illnesses, and eight were military working dogs. Remaining were 207 trauma casualties (96%) and five medical patients (2%). The mean and median times of flight from the injury scene to hospital arrival were less than 20 minutes. Of trauma casualties, most were male US and coalition forces (n = 178; 86%). From this population, injuries to the extremities (n = 139; 67%) were seen most commonly. The primary mechanisms of injury were gunshot wound (n = 89; 43%) and blast injury (n = 82; 40%). The survival rate was 85% (n = 176) for those who incurred trauma. Of those who did not survive, most died before reaching surgical care (26 of 31; 84%).

CONCLUSION

Performance improvement efforts directed toward prehospital combat casualty care can ameliorate survival on the battlefield. Because documentation of care is essential for conducting performance improvement, medical and nonmedical units must dedicate time and efforts accordingly. Capturing and analyzing data from combat missions can help refine tactics, techniques, and procedures and more accurately define wartime personnel, training, and equipment requirements. This study is an example of how performance improvement can be initiated by a nonmedical unit conducting CASEVAC missions.

[Contemporary methodic approach to evaluation of acoustic load on civil aircraft crew members.]

The article characterizes occupational factors including acoustic ones that influence work conditions of civil aircraft crew members, presents methodic basis to evaluate parameters of aviation noise inside cabin, with consideration of additional load from aviaheadsets. To specify scientifically based method for calculating acoustic load on civil aircraft crew members in cabins, the authors measured noise parameters inside cabins of aircrafts used at present in Russia, and noise-proof properties of domestic and foreign aviaheadsets. Normalized values suggested: equivalent level of A sound over a month (LA,,m), over a year (La); suggestions for reference values: equivalent level of A sound (Leg), over an arbitrary period of piloting length (L,r); coefficient of piloting load. Principles of these calculations are determined. The method is designed as an addition to sanitary rules and regulations 2.5.1.2423-08, determining hygienic requirements to work and rest conditions for civil aircraft pilots.

Fighter pilots' heart rate, heart rate variation and performance during instrument approaches

Fighter pilots' heart rate (HR), heart rate variation (HRV) and performance during instrument approaches were examined. The subjects were required to fly instrument approaches in a high-fidelity simulator under various levels of task demand. The task demand was manipulated by increasing the load on the subjects by reducing the range at which they commenced the approach. HR and the time domain components of HRV were used as measures of pilot mental workload (PMWL). The findings of this study indicate that HR and HRV are sensitive to varying task demands. HR and HRV were able to distinguish the level of PMWL after which the subjects were no longer able to cope with the increasing task demands and their instrument landing system performance fell to a sub-standard level. The major finding was the HR/HRV's ability to differentiate the sub-standard performance approaches from the high-performance approaches. Practitioner Summary: This paper examined if HR and HRV were sensitive to varying task demands in a fighter aviation environment and if these measures were related to variations in pilot's performance.

Current concepts of oral and maxillofacial rehabilitation and treatment in aviation

Aerospace medicine is the medical discipline responsible for assessing and conserving the health, safety, and performance of individuals involved in air and space travel. With the upward trend in airline travel, flight-related oral conditions requiring treatment have become a source of concern for aircrew members. Awareness and treatment of any potential physiological problems for these aircrews have always been critical components of aviation safety. In a flight situation, oral and maxillofacial problems may in fact become life-threatening clinical conditions. The unusual nature of aerospace medicine requires practitioners to have unique expertise. Special attention to aerospace medicine will open the way for professionals to develop and apply their skills and capabilities. Both dentists and aviators should be aware of the issues involved in aviation dentistry. This article presents the principles of prevention, treatment guidelines, and dental-related flight restrictions.

[MODERN INSTRUMENTS FOR EAR, NOSE AND THROAT RENDERING AND EVALUATION IN RESEARCHES ON RUSSIAN SEGMENT OF THE INTERNATIONAL SPACE STATION]

The paper reports the results of testing some diagnostic video systems enabling digital rendering of TNT teeth and jaws. The authors substantiate the criteria of choosing and integration of imaging systems in future on Russian segment of the International space station kit LOR developed for examination and download of high-quality images of cosmonauts' TNT, parodentium and teeth.

Evaluation of a strapless heart rate monitor during simulated flight tasks

Pilots are under high task demands during flight. Monitoring pilot's physiological status is very important in the evaluation of pilot's workload and flight safety. Recently, physiological status monitor (PSM) has been embedded into a watch that can be used without a conventional chest strap. This makes it possible to unobtrusively monitor, log and transmit pilot's physiological measurements such as heart rate (HR) during flight tasks. The purpose of this study is to validate HR recorded by a strapless heart rate watch against criterion ECG-derived HR. Ten commercial pilots (mean ± SD : age: 39.1 ± 7.8 years; total flight hours 7173.2 ± 5270.9 hr) performed three routinely trained flight tasks in a full flight simulator: wind shear go-around (WG), takeoff and climb (TC), and hydraulic failure (HF). For all tasks combined (overall) and for each task, differences between the heart rate watch measurements and the criterion data were small (mean difference [95% CI]: overall: -0.71 beats/min [-0.85, -0.57]; WG: -0.90 beats/min [-1.15, -0.65]; TC: -0.69 beats/min [-0.98, -0.40]; HF: -0.61 beats/min [-0.80, -0.42]). There were high correlations between the heart rate watch measurements and the ECG-derived HR for all tasks (r ≥ 0.97, SEE < 3). Bland-Altman plots also show high agreements between the watch measurements and the criterion HR. These results suggest that the strapless heart rate watch provides valid measurements of HR during simulated flight tasks and could be a useful tool for pilot workload evaluation.

Concept of Operations Evaluation for Using Remote-Guidance Ultrasound for Exploration Spaceflight

BACKGROUND

Remote-guidance (RG) techniques aboard the International Space Station (ISS) have enabled astronauts to collect diagnostic-level ultrasound (US) images. Exploration-class missions will likely require nonformally trained sonographers to operate with greater autonomy given longer communication delays (> 6 s for missions beyond the Moon) and blackouts. Training requirements for autonomous collection of US images by non-US experts are being determined.

METHODS

Novice US operators were randomly assigned to one of three groups to collect standardized US images while drawing expertise from A) RG only, B) a computer training tool only, or C) both RG and a computer training tool. Images were assessed for quality and examination duration. All operators were given a 10-min standardized generic training session in US scanning. The imaging task included: 1) bone fracture assessment in a phantom and 2) Focused Assessment with Sonography in Trauma (FAST) examination in a healthy volunteer. A human factors questionnaire was also completed.

RESULTS

Mean time for group B during FAST was shorter (20.4 vs. 22.7 min) than time for the other groups. Image quality scoring was lower than in groups A or C, but all groups produced images of acceptable diagnostic quality.

DISCUSSION

RG produces US images of higher quality than those produced with only computer-based instruction. Extended communication delays in exploration missions will eliminate the option of real-time guidance, thus requiring autonomous operation. The computer program used appears effective and could be a model for future digital US expertise banks. Terrestrially, it also provides adequate self-training and mentoring mechanisms.

[Development of a methodology of for medical-flight examination of flight personnel under condition of hospital]

Development of a methodology of for medical-flight examination of flight personnel under condition of hospital. When performing an experimental study of ways of improvement of hyperbaric ascent involving 95 servicemen,of special contingent determined lack of ascent security of flight crews to altitudes up to 6500 meters due to the large percentage (10%) of revealed reduced hypoxia tolerance of mild and moderate level in military personnel and potentially high risk of high-altitude decompression disease without a preparatory desaturation. The experimental testing of 5 minutes ascent technique for 5000 m and 6000 m is performed, justified criteria of hypobaric hypoxia tolerance of mild and moderate level during the examination of health state of 589 aircrew personnel (including personnel with approved diagnoses) in hyperbaric chamber in relation to hospital conditions. It is experimentally shown that the method of the survey in the chamber on hypoxia tolerance of mild and moderate level in the ascent to the height of 5000 m and 6000 m is an effective mean of determining the functional state and reserve capacity of the organism to identify hidden forms of human diseases and can be used for medical-flight examination of flight personnel in a hospital.

An ergonomics based design research method for the arrangement of helicopter flight instrument panels

In this paper, we study the arrangement of displays in flight instrument panels of multi-purpose civil helicopters following a user-centered design method based on ergonomics principles. Our methodology can also be described as a user-interface arrangement methodology based on user opinions and preferences. This study can be outlined as gathering user-centered data using two different research methods and then analyzing and integrating the collected data to come up with an optimal instrument panel design. An interview with helicopter pilots formed the first step of our research. In that interview, pilots were asked to provide a quantitative evaluation of basic interface arrangement principles. In the second phase of the research, a paper prototyping study was conducted with same pilots. The final phase of the study entailed synthesizing the findings from interviews and observational studies to formulate an optimal flight instrument arrangement methodology. The primary results that we present in our paper are the methodology that we developed and three new interface arrangement concepts, namely relationship of inseparability, integrated value and locational value. An optimum instrument panel arrangement is also proposed by the researchers.

On-Site 3D Printing of Functional Custom Mallet Splints for Mars Analogue Crewmembers

INTRODUCTION

The first off-Earth fused deposition modeling (FDM) 3D printer is investigating acrylonitrile butadiene styrene (ABS) thermoplastic manufacturing applications for long-duration space missions. This study assessed the feasibility of FDM 3D printing ABS thermoplastic customized mallet splints on site for Mars analogue crewmembers.

METHODS

Seven caliper measurements were taken of the right ring finger of 13 healthy Mars Desert Research Station mission crewmembers. These measurements were input into a free 3D modeling software program to create customized digital splint models. These digital files were uploaded to a desktop FDM 3D printer and custom splints were printed on site with ABS thermoplastic. Splint fit was assessed via subject feedback. Joint active range of motion was recorded when the splint was worn briefly.

RESULTS

The time it took the software program to digitally render each splint model was less than 2 min and 30 s. The print duration for the splints ranged from 21 to 29 min. All 13 subjects reported that their 3D printed custom mallet splints fit securely and comfortably. All splints permitted full active range of motion of the proximal interphalangeal joint (0-100°) while maintaining the distal interphalangeal joint in extension.

DISCUSSION

It is feasible to 3D print functional ABS thermoplastic custom mallet splints on site for Mars analogue crewmembers. This technology could be used clinically in the future when a custom mallet splint is required in a remote, resource-constrained setting.

Screening for Sleep Apnea in Morbidly Obese Pilots

BACKGROUND

Debate regarding the merits of screening pilots for sleep apnea has been stimulated by recently issued guidance from the Federal Aviation Administration. It has long been appreciated that sleep apnea results in poor quality sleep, and that poor quality sleep is associated with daytime fatigue and decrements in performance. However, the relationship between sleep apnea and poor performance, including risk for accidents is not as well understood. Good quality data are available for commercial truck drivers and have helped influence transportation policy, but there is a lack of pilot specific data. The purpose of this article is to review the basic epidemiology, pathophysiology, and treatment of sleep apnea, including major risk factors for apnea, such as body mass index (BMI), and to look at what is known about the impact of sleep apnea on performance in transportation related occupations. While pilot specific data may be lacking, good quality data for commercial truckers are available and can be used to formulate rational public policy with the goal of improving aviation safety. This article was reviewed by the Council of the Aerospace Medical Association and approved as a position paper of the Association.

Statistical Evaluation of Causal Factors Associated with Astronaut Shoulder Injury in Space Suits

INTRODUCTION

Shoulder injuries due to working inside the space suit are some of the most serious and debilitating injuries astronauts encounter. Space suit injuries occur primarily in the Neutral Buoyancy Laboratory (NBL) underwater training facility due to accumulated musculoskeletal stress. We quantitatively explored the underlying causal mechanisms of injury.

METHODS

Logistic regression was used to identify relevant space suit components, training environment variables, and anthropometric dimensions related to an increased propensity for space-suited injury. Two groups of subjects were analyzed: those whose reported shoulder incident is attributable to the NBL or working in the space suit, and those whose shoulder incidence began in active duty, meaning working in the suit could be a contributing factor.

RESULTS

For both groups, percent of training performed in the space suit planar hard upper torso (HUT) was the most important predictor variable for injury. Frequency of training and recovery between training were also significant metrics. The most relevant anthropometric dimensions were bideltoid breadth, expanded chest depth, and shoulder circumference. Finally, record of previous injury was found to be a relevant predictor for subsequent injury. The first statistical model correctly identifies 39% of injured subjects, while the second model correctly identifies 68% of injured subjects.

DISCUSSION

A review of the literature suggests this is the first work to quantitatively evaluate the hypothesized causal mechanisms of all space-suited shoulder injuries. Although limited in predictive capability, each of the identified variables can be monitored and modified operationally to reduce future impacts on an astronaut's health.

Challenges of Estimating Fracture Risk with DXA: Changing Concepts About Bone Strength and Bone Density

INTRODUCTION

Bone loss due to weightlessness is a significant concern for astronauts' mission safety and health upon return to Earth. This problem is monitored with bone densitometry (DXA), the clinical tool used to assess skeletal strength. DXA has served clinicians well in assessing fracture risk and has been particularly useful in diagnosing osteoporosis in the elderly postmenopausal population for which it was originally developed. Over the past 1-2 decades, however, paradoxical and contradictory findings have emerged when this technology was widely employed in caring for diverse populations unlike those for which it was developed. Although DXA was originally considered the surrogate marker for bone strength, it is now considered one part of a constellation of factors-described collectively as bone quality-that makes bone strong and resists fracturing, independent of bone density. These characteristics are beyond the capability of routine DXA to identify, and as a result, DXA can be a poor prognosticator of bone health in many clinical scenarios. New clinical tools are emerging to make measurement of bone strength more accurate. This article reviews the historical timeline of bone density measurement (dual X-ray absorptiometry), expands upon the clinical observations that modified the relationship of DXA and bone strength, discusses some of the new clinical tools to predict fracture risk, and highlights the challenges DXA poses in the assessment of fracture risk in astronauts.