INTRODUCTION: Modafinil is used as a countermeasure to limit the effects of fatigue in military aviation. However, literature is conflicting about its negative effects on subsequent sleep.

METHODS: This randomized placebo-controlled trial conducted by the Center of Man in Aviation of the Royal Netherlands Airforce is part of a larger study. It included 32 subjects (mean age 35 yr old, 84% male) who followed a normal daily routine and stayed awake the subsequent night. At midnight, all subjects received either 300 mg caffeine, 200 mg modafinil, or placebo. At the end of the test night, subjects were awake for a median period of 26 h. Afterwards, sleep questionnaires containing qualitative (Groningen Sleep Quality Scale) and quantitative parameters of sleep for the subsequent day (recovery sleep) and consecutive night (post-test sleep) were completed and statistically analyzed using Friedman and Wilcoxon signed rank tests.

RESULTS: A statistically significant difference in the reported recovery sleep was observed. The modafinil group slept 30% shorter than placebo, but sleep efficiency was not statistically different. Quantitatively post-test sleep did not vary statistically significantly between the three groups. However, Groningen Sleep Quality Scale scores were lower post-test than pre-test in the modafinil group, while this was not the case in the caffeine and placebo group.

DISCUSSION:This study found that modafinil subjectively does not negatively impact recovery sleep or subsequent nighttime sleep after an extended period of wakefulness and suggests it may decrease the need for recovery sleep compared to placebo or caffeine.

Wingelaar-Jagt YQ, Wingelaar TT, Riedel WJ, Ramaekers JG. Modafinil subjectively does not impair sleep in aviators after a period of extended wakefulness. Aerosp Med Hum Perform. 2024; 95(6):290–296.

INTRODUCTION: Negative pressure breathing is breathing with decreased pressure in the respiratory tract without lowering pressure acting on the torso. We lowered air pressure only during inspiration (NPBin). NPBin, used to increase venous return to the heart, is considered a countermeasure against redistribution of body fluids toward the head during spaceflight. We studied NPBin effects on circulation in healthy humans with an emphasis on NPBin-induced oscillations of hemodynamic parameters synchronous with breathing. We propose an approach to analyze the oscillations based on coherent averaging.

METHODS: Eight men ages 24–42 yr participated in the NPBin and control series. During the series, to reproduce fluids shift observed under microgravity, subjects were supine and head down (−8°). Duration of NPBin was 20 min, rarefaction −20 cm H₂O. Hemodynamic parameters were measured by Finometer. Electrical impedance measurements were used to estimate changes in blood filling of cerebral vessels.

RESULTS: Mean values of hemodynamic parameters virtually did not change under NPBin, but NPBin induced oscillations of the parameters synchronous with respiration. Peak-to-peak amplitude under NPBin were: mean arterial pressure, 4 ± 1 (mmHg); stroke volume, 7 ± 3 (mL); and heart rate, 4 ± 1 (bpm). Electrical impedance of the head increased during inspiration. The increase under NPBin was three times greater than under normal breathing.

DISCUSSION: Analysis of oscillations gives more information than analysis of mean values. NPBin induces short-term decrease in left ventricle stroke volume and arterial blood pressure during each inspiration; the decrease is compensated by increase after inspiration. NPBin facilitates redistribution of body fluids away from the head.

Semenov YS, Melnikov IS, Luzhnov PV, Dyachenko AI. Oscillations of hemodynamic parameters induced by negative pressure breathing in healthy humans. Aerosp Med Hum Perform. 2024; 95(6):297–304.

INTRODUCTION: Agricultural aircraft operations are associated with unique challenges. In particular, these include maintaining awareness of obstacles associated with flight at very low altitudes. Wire strikes are a common cause of accidents in these operations.

METHODS: Focus groups were completed during the 2022 Ag Aviation Expo hosted by the National Agricultural Aviation Association with pilots who had experienced wire-strike events (N = 22). The researchers coded the transcripts using a human factors framework.

RESULTS: Notably, unplanned “trim passes” were a key stage of flight during wire-strike events. Cognitive risk factors that may have affected their performance included situation awareness, decision-making choices, and pressure to perform. Over half of subjects reported being aware of the wire before collision. Possible prevention strategies include not spraying the field due to safety risks, paying better attention to where they were in the field, and avoiding deviation from the planned route.

DISCUSSION: Wire-strike events often occur due to momentary lapses in attention, even when the pilot is already aware of the wire. This study shows that targeted approaches to prevent wire strikes in agricultural aviation operations require addressing a number of cognitive risks and human factors, rather than implementing increased preflight surveillance. These results have implications for preventing future wire-strike accidents based directly on pilot perceptions, both within agricultural operations and general aviation more broadly.

Baumgartner HM, DiDomenica R, Hu PT, Thomas S. Pilot perceptions of wire strikes in agricultural aviation operations. Aerosp Med Hum Perform. 2024; 95(6):305–312.

INTRODUCTION: An Australasian Airline’s Alcohol and Other Drug (AOD) Program demonstrates abstinence rates that exceed those of general AOD programs. The reasons for this are unclear. The purpose of this research was to develop a theory as to why this program is successful.

METHODS: A qualitative examination following grounded theory methodology was undertaken. AOD program patients and healthcare professionals were interviewed until content saturation was reached. Data analysis followed grounded theory to identify the key concepts associated with the program’s success.

RESULTS: The core theory that emerged highlighted the pivotal roles of a strong employee–company relationship, shared values, and a safety-focused culture in explicating the program’s success. This moves beyond the “carrot and stick” model of motivation, where belonging to this organization and safety consciousness serve as powerful drivers for abstinence. Challenges and barriers highlighted some unique challenges to the program in managing the coronavirus pandemic and the difference in approach to substance use in community spaces versus safety-critical employment.

DISCUSSION: This research expands the understanding of this AOD program’s success in a safety-critical industry, emphasizing the elements of a working relationship that are beyond positive or negative reinforcement. Future research should work to quantify and test the generalizability of these findings.

Nairn J, Bell E, Myers J, Higgins M, Johnston B, Newton-Howes G. A grounded theory exploration of addictions treatment within a commercial airline setting. Aerosp Med Hum Perform. 2024; 95(6):313–320.

INTRODUCTION: On-board medical emergencies are increasing. Different geographies have different legislation and requirements for medical emergency kits and first aid kits. A comprehensive review to compare the contents of both kits was conducted, including the International Air Transport Association, European Union Aviation Safety Agency, and Federal Aviation Administration, as well as some from other geographical areas of the globe to cover continents and regions with the highest air traffic, such as Brazil, Kenya, Australia, and Taiwan.

METHODS: On June 10, 2023, a search was conducted using standardized medical terms (medical subject headings) within the PubMed^® database. The relevant terms identified were “Aircraft” and “Medical Emergencies”; articles published within the last 10 yr were filtered. Subsequently, even articles published before 2013 were consulted if cited by the initial ones. The main regulatory entities’ documentation was found using the Google search engine and consulted.

CONCLUSIONS: It is impossible to be prepared for every emergency on board. Still, as doctors, we have a moral and ethical obligation to try to improve the outcomes of those emergencies. Getting a standardized report of every on-board emergency is crucial. That would make optimizing the items to include in the emergency and first aid kits easier. There are many similarities among the compared entities, but essential differences have been found. There is room for improvement, especially for pediatric travelers.

Oliveira ATB. Worldwide regulation of the medical emergency kit and first aid kit. Aerosp Med Hum Perform. 2024; 95(6):321–326.

INTRODUCTION: The absence of a consistent downward G vector can make separation of gases from liquids challenging, such as in field medicine without stable upright equipment or during spaceflight. This limits the use of medical equipment and procedures like administration of intravenous (IV) fluids in microgravity and can make field medicine hazardous. Administering IV fluids and medications in microgravity requires a technique to separate air from the liquid phase. Current commercial filters for separation of gases are incompatible with high flow and blood. We present a novel filter designed to provide adequate air clearance without a consistent downward G vector.

METHODS: Inline air-eliminating filters were designed for use with IV fluid tubing in microgravity using computer-aided design software and printed using nylon 12 on an EOS Selective Laser Sintering 3D printer. A 0.2-μm membrane filter was adhered around a central, hollow pillar with external spiral baffles allowing separation and venting of air from the fluid. Results were compared against commercially available inline air-eliminating filters.

RESULTS: The 3D-printed filters outperformed the commercial filters in both percentage of air removed and flow rates. The centrifugal, baffled filter had flow rates that far exceeded the commercial filters during rapid transfusion.

DISCUSSION: IV fluid administration is an often underappreciated and a necessary basic requirement for medical treatment. An air-eliminating filter compatible with blood and rapid transfusion was developed and validated with crystalloid solutions to allow the successful administration of IV fluid and medication without a consistent downward G vector.

Formanek A, Townsend J, Ottensmeyer MP, Kamine TH. A novel 3D-printed gravity-independent air-eliminating filter for rapid intravenous infusions. Aerosp Med Hum Perform. 2024; 95(6):327–332.

BACKGROUND: In the literature, central serous retinopathy (CSR) accompanying solitary fibrous tumors (SFT) in a pilot has not been reported. In airline pilots, mass effect-related symptoms such as diplopia, ptosis, etc., seen with orbital tumors may endanger flight safety.

CASE REPORT: A 62-yr-old male commercial airline pilot presented with blurred vision in the right eye. He had been receiving treatment for 2 mo because of CSR. His visual acuity was 10/20 in the right eye and 20/20 in the left. During examination, ptosis and exophthalmos were noticed in the right eye. Ocular movements were free in all cardinal directions and there was downward displacement in the right eye. There was no diplopia. Magnetic resonance imaging revealed a 1.5- to 2-cm well-defined contrast-enhancing mass in the lateral extraconal orbit. His medical flight certificate was suspended for 3 mo due to decreased visual acuity and superior visual defect. Superior orbitotomy was performed without any complication. Ptosis and CSR had regressed 1 wk after surgery. All systemic and ophthalmological examinations met aviation medical certificate requirements. He returned to flight on the condition of being checked every 3 mo. At the 1-yr follow-up, there was no sign of recurrences of SFT or CSR.

DISCUSSION: SFTs are slow-growing neoplasms that can manifest symptoms related to mass effect. In the current literature, there are no reported cases of the coexistence of orbital SFT and CSR or pilots able to resume flight duties only 1 wk after a successful orbitotomy and tumor resection surgery.

Altinbas M, Ozpınar A, Akbaba M, Nacaroglu SA, Sargolzaeimoghaddam M, Sargolzaeimoghaddam M. Orbital solitary fibrous tumor in a commercial airline pilot. Aerosp Med Hum Perform. 2024; 95(6):333–336.

BACKGROUND: Functional dyspepsia is a disorder of gut–brain interaction that has the potential to impact aviation performance. Proton pump inhibitors are well-tolerated but are only effective in one half of cases. Second-line treatments, including tricyclic antidepressants, are associated with drowsiness and are not routinely approved for use in aviators. We present a case of a Naval Flight Officer with functional dyspepsia who was successfully treated with amitriptyline and returned to flying status.

CASE REPORT: A 23-yr-old male Naval Flight Officer presented with postprandial fullness and epigastric pain. His symptoms were refractory to trials of acid suppression and lifestyle modification. An extensive evaluation by Gastroenterology, including upper endoscopy, did not reveal an organic cause of his symptoms and he was diagnosed with functional dyspepsia. The patient’s symptoms resolved with a trial of amitriptyline. Neuropsychological testing demonstrated no medication effect on cognitive performance. A waiver to resume flying duties on amitriptyline was submitted to the Naval Aerospace Medical Institute and was approved.

DISCUSSION: We present the second known waiver issued in U.S. Naval aviation history for the use of amitriptyline to treat a gastrointestinal disorder. Amitriptyline is not commonly waived due to the potential for unacceptable cognitive side-effects in the flight environment. However, neuropsychological testing to assess for a possible medication effect on performance can be used to inform an aeromedical disposition and, in this case, allowed for a return to flight status.

Crutcher R, Kolasinski N. Functional dyspepsia and tricyclic antidepressant use in a naval flight officer. Aerosp Med Hum Perform. 2024; 95(6):337–340.