BACKGROUND: Maintenance and disposition of decedent remains during spaceflight require the isolation of biohazardous products of decomposition in microgravity and in the absence of refrigeration. Containment and isolation options would preferably offer sufficient time to enable crew and ground support teams to determine appropriate disposition of remains and even potentially return remains to the Earth. The pilot study described herein undertook an effort to develop a postmortem containment unit for the isolation and maintenance of decedent remains in a microgravity environment.

METHODS: Commercial off-the-shelf containment units were modified to meet the needs of a microgravity spaceflight environment and to offer the best likelihood of successful containment and management of remains. A subsequent evaluation of modified containment unit performance was undertaken utilizing human cadavers, with measurement and analysis of volatile off-gassing over time followed by impact testing of the units containing cadaverous remains in a simulated spaceflight vehicle seat.

RESULTS: Modifications were implemented without significant negative design impact. Failure was observed in one modified unit after 9 d and attributed to improper filter application. The remaining unit successfully contained remains beyond the intended endpoint of the study.

DISCUSSION: These pilot efforts offer important insight into the development of effective postmortem containment options for future spaceflight. Further study is needed to ensure repeatability of the findings and to further characterize the failure modes of the modified units evaluated, the impact of microgravity conditions, and the identification of additional modifications that would improve remains disposition.

Houser T, Lindgren KN, Mazuchowski EL II, Barratt MR, Haines DC, Jayakody M, Blue RS, Bytheway JA, Stepaniak PC. Remains containment considerations for death in low-Earth orbit. Aerosp Med Hum Perform. 2023; 94(5):368–376.

BACKGROUND: Spatial disorientation (SD) remains a stubborn and formidable challenge among rotary wing (RW) aircrews, particularly during times of high workload and deceptive visual cues. With tri-Service agreement, British RW Forces employ a layered training approach that now includes simulator-based immersive scenarios.

METHODS: Ten bespoke RW SD training scenarios were developed for the AW159 Wildcat helicopter simulator by a multidisciplinary team. Scenarios were embedded within advanced training packages that were not solely focused on SD. A voluntary, anonymous survey instrument was distributed post-SD sortie to assess hazard awareness, training effectiveness, role and mission relevance, and perceived ability to respond to future SD threat. A corresponding assessment from the simulator instructor was used for independent determination if the crew became disoriented during the training.

RESULTS: Over a 6-mo training cycle, 69 surveys were completed. Seven-point Likert-scale assessments yielded elevated median scores (6.0, respectively) across all four categories, suggesting favorable aircrew perceptions of training objective success. Elevated scoring of previous SD training received suggests good penetrance among the RW community surveyed. Of all sorties flown, the majority of aircrew (68%) became disoriented at some point during the sortie.

DISCUSSION: This report provides limited evidence in support of bespoke SD training scenarios within a synthetic training environment. The merits include flexible ability to address root causes, provision of an interactive and immersive environment, and compatibility with extant tactics and mission configurations. SD simulator-based training can serve as an important component of a layered, multimodal approach.

Bushby AJR, Gaydos SJ. Spatial disorientation scenarios for the AW159 helicopter within a synthetic training environment. Aerosp Med Hum Perform. 2023; 94(5):377–383.

INTRODUCTION: Prolonged exposure to microgravity is associated with a significant reduction in bone density, exposing astronauts to renal calculi in flight and osteoporotic fractures on return to Earth. While physical countermeasures and bisphosphonates may reduce demineralization, additional therapies are needed for future interplanetary missions. This literature review aims to understand the current background pertaining to denosumab (a monoclonal antibody therapy used in osteoporosis) and its potential use for long duration spaceflight.

METHOD: A literature review was conducted using the following keywords: “osteoporosis”; “osteopaenia”; “microgravity”; “space flight”; “bed rest”; “denosumab”; “alendronate”; “bisphosphonates”; and “countermeasures”. Additional articles were identified through references. Included for discussion were 48 articles, including systemic reviews, clinical trials, practice guidelines, and textbooks.

RESULTS: No previous bed rest or in-flight studies regarding denosumab were identified. In osteoporosis, denosumab is superior to alendronate in maintaining bone density with a lower rate of side-effects. Emerging evidence in reduced biomechanical loading state suggests denosumab improves bone density and decreases fracture risk. Concerns exists over vertebral fracture risk following discontinuation. The dosing regimen of denosumab offers practical advantages over bisphosphonates. Existing spaceflight studies with alendronate serve as a template for a study with denosumab and allow for a direct comparison of efficacy and safety.

DISCUSSION: Denosumab has numerous potential advantages as a countermeasure to microgravity-induced osteopenia when compared to alendronate, including: improved efficacy; fewer side-effects: better tolerability; and a convenient dosing regimen. Two further studies are proposed to determine in-flight efficacy and the suitability of monoclonal antibody therapy in the spaceflight environment.

Rengel A, Tran V, Toh LS. Denosumab as a pharmacological countermeasure against osteopenia in long duration spaceflight. Aerosp Med Hum Perform. 2023; 94(5):389–395.

INTRODUCTION: During a deployment of a fighter unit, aircrew began to exhibit ear discomfort and episodes of auricular irritation and ulceration. All affected were using the Attenuating Custom Communications Earpiece System (ACCES). Discomfort was previously discussed in the literature, but neither the prevalence of discomfort nor the occurrence of skin ulcerations had been previously described.

METHODS: An anonymous paper questionnaire was used with three fighter squadrons while deployed in 2019. A total of 59 aircrew in the F-15C/E and F-16 airframes participated; aircrew not using ACCES were excluded.

RESULTS: Response rate was 57.3%, spread evenly among airframes, with 78% being pilots. A majority of respondents (79.7%) stated they had ACCES problems in the deployed setting. Among those noting problems in the deployed setting, 89% reported ear discomfort and a smaller portion reported skin redness, erosion, and bleeding.

DISCUSSION: This study was able to provide a small sample estimate of the prevalence of ear problems among fighter aircrew ACCES users while deployed. This sample exhibited an increase in prevalence of ear discomfort during the deployment. It also showed pathological features absent in home-station flying, such as skin redness and erosion. However, the sample size and study design prevented risk factor characterization, confounder control, or causal inference. While ACCES may contribute to these problems, other confounders such as air characteristics, recall bias, aircrew motivation to report problems, and baseline dermatologic pathology could not be excluded. This data should serve as a baseline for larger studies, which are better equipped for confounder control and assessment of other potential risk factors.

Strawbridge PA, Steinkraus LW, Girsch RM. Skin pathology prevalence in deployed fighter aircrew using custom molded hearing protection. Aerosp Med Hum Perform. 2023; 94(5):396–399.

INTRODUCTION: Facial nerve palsy has been observed sporadically by aviation medicine doctors in recent years. We present two case reports of patients with the rare condition of facial nerve palsy occurring during aviation, along with a review of the literature, an overview of the phenomenon and the described symptoms of the cases. PubMed^® including Medline^® was searched using the terms nerve palsy and aviation with no restriction. In addition, two new cases of recurrent nerve palsy are described.

CASE REPORTS: We describe two case reports: A 20-yr-old woman reported recurrent transient left-sided facial nerve palsy with increased duration and intensity on four subsequent flights, and a 35-yr-old woman who reported a left-sided transient facial nerve palsy 20 min after ascent.

DISCUSSION: Included in the systematic review were 17 studies. Only case report studies were found. Including the two cases of facial nerve palsy described in this article, the reviewed studies represent 23 cases of peer-reviewed facial baro-palsy in aviation (ages 10 to 62 yr old). Having baro-palsy symptoms during flight is a rare condition, and the mechanism is not well understood. Some typical characteristics and possible mechanisms are discussed. PE tube insertion of the tympanic membrane has been found to be an effective treatment; however, further studies are needed.

Bloch SL, Hertz J, Klokker M. Transient facial nerve palsy in aviation. Aerosp Med Hum Perform. 2023; 94(5):404–408.

BACKGROUND: There is continued interest in acceleration (G) effects in civil aviation, as G-induced loss of consciousness (G-LOC), impaired consciousness, and visual effects play a role in aerobatic, agricultural, and military aviation accidents.

METHODS: A software model [the Civil Aerospace Medical Institute G-Effects Model (CGEM)] based on physical and physiological variables related to in-flight tissue resupply and using oxygen flow as a proxy for supply availability, was developed to evaluate risk of G-LOC and related phenomena in aeronauts. Aeronauts were modeled using several parameters, including sex, cardiovascular fitness, and other common modifiers such as G-suits, positive pressure breathing gear, anti-G straining, and other muscle tensing. The software was validated by comparison with experimental data from the peer-reviewed literature.

RESULTS: CGEM predicted physiological effects of G_z exposure accurately, particularly for rapid onset rates. Predicted times to G-LOC and absolute incapacitation periods were consistently within 1 SD of pooled results obtained during centrifuge experiments using U.S. Navy (USN) and U.S. Air Force (USAF) pilots. Predictions of G tolerance based on visual effects onset also compared well with published data, as did evaluation of symptoms expected during a difficult aerobatic maneuver.

DISCUSSION: CGEM is a new tool for civil and military aviation. Rather than providing a simple G tolerance number, flight surgeons, pilots, and accident investigators can gain insight into changes in risk—from factors such fatigue, medications, dehydration, and anti-G countermeasures used—through proper selection of parameters.

Copeland K, Whinnery JE. Cerebral blood flow based computer modeling of G_z-induced effects. Aerosp Med Hum Perform. 2023; 94(5):409–414.