Assessment of Sex-Dependent Medical Outcomes During Spaceflight.

Background: In this study sex-differences in medical outcomes during spaceflight are reviewed and probabilistic risk assessment (PRA) is used to assess the impact on spaceflight missions of varying lengths. Materials and Methods: We use PRA to simulate missions of 42 days, 6 months, and 2.5 years. We model medical outcomes using three crews: two men and two women, four women, or four men. Total medical events (TME), crew health index (CHI), probability (0-1) of medical evacuation (pEVAC), probability of loss of crew life (pLOCL), and influential medical conditions were determined. Results: No differences were seen in any metric for the 42-day mission. There were no differences seen for any mission length, in any crew, for TME, CHI, pLOCL, or environmental causes of pEVAC. Sex-dependent differences are seen for rates of nonemergent pEVAC during the 6 month and 2.5-year missions, where women have a higher pEVAC in the 182-day (0.0388 vs. 0.0354) and 2.5-year missions (0.350 vs. 0.228). These differences were driven by higher incidence of partially treated urinary tract infection (UTI). In the 2.5 year mission, with resupply of medical resources, the influence of UTI in women on pEVAC decreases (0.35-0.11). Conclusion: Although resupply is unlikely for deep space missions, modeled results suggest that sex-specific medical needs can be readily managed through preventive measures and inclusion of appropriate medical capabilities. Within its many limitations, PRA is a useful tool to estimate medical risks in unique environments where only expert opinion was previously available.

Probabilistic Risk Assessment of Prophylactic Surgery Before Extended-Duration Spaceflight.

Introduction. Prophylactic surgery before spaceflight may eliminate the risk of appendicitis and cholecystitis in astronauts on deep space missions. However, even minimally invasive surgery increases the risk of small bowel obstruction (SBO). Probabilistic risk assessment (PRA) is a method that can be used to estimate the benefits and risks of prophylactic surgery. Methods. Risks of appendicitis and cholecystitis during a 2.5-year Mars mission are compared to the risk of SBO after laparoscopic removal of the appendix, gallbladder, or both. A PRA model using Monte Carlo methodology was used to forecast the risks. Results. Prophylactic appendectomy and cholecystectomy combined, conferred an increased probability of medical evacuation (pEVAC) due to SBO as compared to the no surgery group. A slightly higher probability for the loss of crew life (pLOCL) was found in the no surgery group when compared to the cases in which either prophylactic appendectomy alone, or appendectomy plus cholecystectomy are performed. Discussion. The need for medical evacuation can be viewed as a potential risk for death in the context of a space mission where evacuation is not possible. Because of the higher pEVAC due to SBO and relatively small benefit in the reduction of pLOCL in the prophylactic surgery groups, this analysis does not support the prophylactic removal of appendix and/or gallbladder for spaceflight. Future advances in surgical or medical technique or mission medical capabilities may change these results. This work demonstrates the utility of PRA in providing quantitative answers to "what if" questions where limited information is available.

Challenges in Clinical Management of Radiation-Induced Illnesses During Exploration Spaceflight.

INTRODUCTION: Analysis of historical solar particle events (SPEs) provides context for some understanding of acute radiation exposure risk to astronauts who will travel outside of low-Earth orbit. Predicted levels of radiation exposures to exploration crewmembers could produce some health impacts, including nausea, emesis, and fatigue, though more severe clinical manifestations are unlikely. Using current models of anticipated physiological sequelae, we evaluated the clinical challenges of managing radiation-related clinical concerns during exploration spaceflight.METHODS: A literature review was conducted to identify terrestrial management standards for radiation-induced illnesses, focusing on prodromal symptom treatment. Terrestrial management was compared to current spaceflight medical capabilities to identify gaps and highlight challenges involved in expanding capabilities for future exploration spaceflight.RESULTS: Current spaceflight medical resources, such as those found on the International Space Station, may be sufficient to manage some aspects of radiation-induced illness, although effective treatment of all potential manifestations would require substantial expansion of capabilities. Terrestrial adjunctive therapies or more experimental treatments are unavailable in current spaceflight medical capabilities but may have a role in future management of acute radiation exposure.DISCUSSION: Expanded medical capabilities for managing radiation-induced illnesses could be included onboard future exploration vehicles. However, this would require substantial research, time, and funding to reach flight readiness, and vehicle limitations may restrict such capabilities for exploration missions. The benefits of including expanded capabilities should be weighed against the likelihood of significant radiation exposure and extensive mission design constraints.Blue RS, Chancellor JC, Suresh R, Carnell LS, Reyes DP, Nowadly CD, Antonsen EL. Challenges in clinical management of radiation-induced illnesses during exploration spaceflight. Aerosp Med Hum Perform. 2019; 90(11):966-977.

Blood transfusion for deep space exploration.

BACKGROUND: Astronauts on exploration missions may be at risk for traumatic injury and medical conditions that lead to life threatening hemorrhage. Resuscitation protocols are limited by the austere conditions of spaceflight. Solutions may be found in low-resource terrestrial settings. The existing literature on alternative blood product administration and walking blood banks was evaluated for applicability to spaceflight. STUDY DESIGN AND METHODS: A literature review was done using PubMed and Google Scholar. References were crosschecked for additional publications not identified using the initial search terms. Twenty-seven articles were identified, including three controlled trials, six retrospective cohort analyses, 15 reviews, one case report, and two experimental studies. RESULTS: Solutions to blood transfusion in austere settings include lyophilized blood products, hemoglobin-based oxygen carriers (HBOCs), and fresh whole blood. Many of these products are investigational. Protocols for walking blood banks include methods for screening and activating donors, transfusion, and monitoring for adverse reactions. Microgravity and mission limitations create additional challenges for transfusion, including baseline physiologic changes, difficulty reconstituting lyophilized products, risk of air emboli during transfusion, equipment constraints, and limited evacuation and surgical options. CONCLUSION: Medical planning for space exploration should consider the possibility of acute blood loss. A model for "floating" blood banks based on terrestrial walking blood bank protocols from austere environments is presented, with suggestions for future development. Constraints on volume, mass, storage, and crew, present challenges to blood transfusion in space and must be weighed against the benefits of expanding medical capabilities.

Clinical Herpes Zoster in Antarctica as a Model for Spaceflight.

INTRODUCTION: Antarctica is a useful analog for spaceflight, as both environments are remote, isolated, and with limited resources. While previous studies have demonstrated increased asymptomatic viral shedding in both the Antarctic and spaceflight environments, clinical manifestations of reactivated viral disease have been less frequently identified. We sought to identify the incidence of clinical herpes zoster from viral reactivation in the Antarctic winter-over population. METHODS: Medical records from the 2014 winter season were reviewed for the incidence of zoster in U.S. Antarctic personnel and then compared to the age-matched U.S. RESULTS: Five cases of clinical herpes zoster occurred in the Antarctic Station population of 204 persons, for an incidence of 33.3 per 1000 person-years vs. 3.2 per 1000 person-years in the general population. Four cases were in persons under age 40, yielding an incidence of 106.7 per 1000 person-years in persons ages 30-39 compared to an incidence of 2.0 per 1000 person-years in the same U.S. age group. DISCUSSION: Immune suppression due to the stressful Antarctic environment may have contributed to the increased incidence of herpes zoster in U.S. Antarctic personnel during the winter of 2014. Working and living in isolated, confined, and extreme environments can cause immune suppression, reactivating latent viruses and increasing viral shedding and symptomatic disease. Such changes have been observed in other austere environments, including spaceflight, suggesting that clinical manifestations of viral reactivation may be seen in future spaceflight.Reyes DP, Brinley AA, Blue RS, Gruschkus SK, Allen AT, Parazynski SE. Clinical herpes zoster in Antarctica as a model for spaceflight. Aerosp Med Hum Perform. 2017; 88(8):784-788.

Centrifuge-simulated suborbital spaceflight in subjects with cardiac implanted devices.

INTRODUCTION: Future commercial spaceflight participants (SFPs) with conditions requiring personal medical devices represent a unique challenge. The behavior under stress of cardiac implanted devices (CIDs) such as pacemakers is of special concern. No known data currently exist on how such devices may react to the stresses of spaceflight. We examined the responses of two volunteer subjects with CIDs to G forces in a centrifuge to evaluate how similar potential commercial SFPs might tolerate the forces of spaceflight. CASE REPORT: Two subjects, 75- and 79-yr-old men with histories of atrial fibrillation and implanted dual-lead, rate-responsive pacemakers, underwent seven centrifuge runs over 2 d. Day 1 consisted of two +Gz runs (peak = +3.5 Gz, run 2) and two +Gx runs (peak = +6.0 Gx, run 4). Day 2 consisted of three runs approximating suborbital spaceflight profiles (combined +Gx/+Gz). Data collected included blood pressures, electrocardiograms, pulse oximetry, neurovestibular exams, and postrun questionnaires regarding motion sickness, disorientation, greyout, and other symptoms. Despite both subjects' significant medical histories, neither had abnormal physiological responses. Post-spin analysis demonstrated no lead displacement, damage, or malfunction of either CID. DISCUSSION: Potential risks to SFPs with CIDs include increased arrhythmogenesis, lead displacement, and device damage. There are no known prior studies of individuals with CIDs exposed to accelerations anticipated during the dynamic phases of suborbital spaceflight. These cases demonstrate that even individuals with significant medical histories and implanted devices can tolerate the acceleration exposures of commercial spaceflight. Further investigation will determine which personal medical devices present significant risks during suborbital flight and beyond.

Implanted medical devices in the radiation environment of commercial spaceflight.

INTRODUCTION: Some commercial spaceflight participants (SFPs) may have medical conditions that require implanted medical devices (IMDs), such as cardiac pacemakers, defibrillators, insulin pumps, or similar electronic devices. The effect of space radiation on the function of IMDs is unknown. This review will identify known effects of terrestrial and aviation electromagnetic interference (EMI) and radiation on IMDs in order to provide insight into the potential effects of radiation exposures in the space environment. METHODS: A systematic literature review was conducted on available literature on human studies involving the effects of EMI as well as diagnostic and therapeutic radiation on IMDs. RESULTS: The literature review identified potential transient effects from EMI and diagnostic radiation levels as low as 10 mGy on IMDs. High-energy, therapeutic, ionizing radiation can cause more permanent device malfunctions at doses as low as 40 mGy. Radiation doses from suborbital flight altitudes and durations are anticipated to be less than those experienced during an average round-trip, cross-country airline flight and are unlikely to result in significant detriment, though longer, orbital flights may expose SFPs to doses potentially harmful to IMD function. DISCUSSION: Individuals with IMDs should experience few, if any, radiation-related device malfunctions during suborbital flight, but could have problems with radiation exposures associated with longer, orbital flights.

Tolerance of centrifuge-simulated suborbital spaceflight by medical condition.

INTRODUCTION: We examined responses of volunteers with known medical disease to G forces in a centrifuge to evaluate how potential commercial spaceflight participants (SFPs) might tolerate the forces of spaceflight despite significant medical history. METHODS: Volunteers were recruited based upon suitability for each of five disease categories (hypertension, cardiovascular disease, diabetes, lung disease, back or neck problems) or a control group. Subjects underwent seven centrifuge runs over 2 d. Day 1 consisted of two +G(z) runs (peak = +3.5 G(z), Run 2) and two +G(x), runs (peak = +6.0 G(x), Run 4). Day 2 consisted of three runs approximating suborbital spaceflight profiles (combined +G(x) and +G(z), peak = +6.0 G(x)/+4.0 G(z)). Data collected included blood pressure, electrocardiogram, pulse oximetry, neurovestibular exams, and post-run questionnaires regarding motion sickness, disorientation, grayout, and other symptoms. RESULTS: A total of 335 subjects registered for participation, of which 86 (63 men, 23 women, age 20-78 yr) participated in centrifuge trials. The most common causes for disqualification were weight and severe and uncontrolled medical or psychiatric disease. Five subjects voluntarily withdrew from the second day of testing: three for anxiety reasons, one for back strain, and one for time constraints. Maximum hemodynamic values recorded included HR of 192 bpm, systolic BP of 217 mmHg, and diastolic BP of 144 mmHg. Common subjective complaints included grayout (69%), nausea (20%), and chest discomfort (6%). Despite their medical history, no subject experienced significant adverse physiological responses to centrifuge profiles. DISCUSSION: These results suggest that most individuals with well-controlled medical conditions can withstand acceleration forces of launch and re-entry profiles of current commercial spaceflight vehicles.

Practice-based electronic billing systems and their impact on immunization registries.

Many providers rely on electronic billing systems to report information to immunization registries. If billing data fail to capture some administered immunizations, the registry will not reflect a child's true immunization status. Our objective was to assess differences between immunizations administered and immunizations reported to a registry from electronic billing systems. Philadelphia's Department of Public Health conducted chart audits in 45 providers serving 50 or more children aged 7-35 months and using electronic billing systems to report data to Philadelphia's immunization registry in 2001-2003. Chart records were compared to registry records to identify immunizations administered in these practices but not reported to the registry. The study practices administered 256,969 immunizations to 20,611 children. Of these 256,969 administered immunizations, 62,213 (24%) were not in the registry. The electronic billing systems submitted data for all administered immunizations for 69% of immunization visits, some but not all for 11% of visits, and none for 20% of visits. Immunizations administered but not billed cost these providers up to $980,477 in lost revenue from administrative fees alone. Improvement of billing data quality would result in more complete registries, higher reported immunization coverage rates, and recovered revenue for immunization providers.