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Caffeine has been suggested to act as a countermeasure against fatigue in military operations. In this randomized, double-blind, placebo-controlled study, the effect of caffeine on simulator flight performance was examined in 13 military pilots during 37 hours of sleep deprivation. Each subject performed a flight mission in simulator four times. The subjects received either a placebo (six subjects) or 200 mg of caffeine (seven subjects) 1 hour before the simulated flights. A moderate 200 mg intake of caffeine was associated with higher axillary temperatures, but it did not affect subjectively assessed sleepiness. Flight performance was similar in both groups during the four rounds flown under sleep deprivation. However, subjective evaluation of overall flight performance in the caffeine group tended to be too optimistic, indicating a potential flight safety problem. Based on our results, we do not recommend using caffeine pills in military flight operations. [ABSTRACT FROM AUTHOR]

Understanding the operator's cognitive workload is crucial for efficiency and safety in human-machine systems. This study investigated how cognitive workload modulates cardiac autonomic regulation during a standardized military simulator flight. Military student pilots completed simulated flight tasks in a Hawk flight simulator. Continuous electrocardiography was recorded to analyze time and frequency domain heart rate variability (HRV). After the simulation, a flight instructor used a standardized method to evaluate student pilot's individual cognitive workload from video-recorded flight simulator data. Results indicated that HRV was able to differentiate flight phases that induced varying levels of cognitive workload; an increasing level of cognitive workload caused significant decreases in many HRV variables, mainly reflecting parasympathetic deactivation of cardiac autonomic regulation. In conclusion, autonomic physiological responses can be used to examine reactions to increased cognitive workload during simulated military flights. HRV could be beneficial in assessing individual responses to cognitive workload and pilot performance during simulator training., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

BACKGROUND: In military aviation, due to high-altitude flight operations, hypoxia training is mandatory and nowadays is mainly done as normobaric hypoxia training in flight simulators. During the last decade, scientific data has been published about delayed recovery after normobaric hypoxia, known as a "hypoxia hangover." Sopite syndrome is a symptom complex that develops as a result of exposure to real or apparent motion, and it is characterized by yawning, excessive drowsiness, lassitude, lethargy, mild depression, and a reduced ability to focus on an assigned task. CASE REPORT: In this study, we present the case of a 49-yr-old pilot who participated in normobaric hypoxia refreshment training in an F/A-18C Hornet simulator and experienced delayed drowsiness, even 3 h after the training. DISCUSSION: This case report demonstrates the danger of deep hypoxia. Hypoxia training instructions should include restrictions related to driving a car immediately after hypoxia training. In addition, hypoxia may lower the brain threshold for sopite syndrome. Varis N, Leinonen A, Perälä J, Leino TK, Husa L, Sovelius R. Delayed drowsiness after normobaric hypoxia training in an F/A-18 Hornet simulator . Aerosp Med Hum Perform. 2023; 94(9):715-718.

INTRODUCTION: Physiological episodes are an issue in military aviation. Some non-pressure-related in-flight symptoms are proved to be due to hyperventilation rather than hypoxia. The aim of this study was to validate a new training method provoking hyperventilation during normobaric hypoxia (NH) training in an F/A-18 Hornet simulator. METHODS: In a double-blind setting, 26 fighter pilots from the Finnish Air Force performed 2 setups in a WTSAT simulator in randomized order with full flight gear. Without the pilot's knowledge, 6% O₂ in nitrogen or 6% O₂ + 4% CO₂ in nitrogen was turned on. Ventilation (VE) was measured before, during, and after hypoxia. S p o₂ and ECG were monitored and symptoms documented. The subjects performed a tactical identification flight until they recognized symptoms of hypoxia. Thereafter, they performed hypoxia emergency procedures with 100% O₂ and returned to the base with a GPS malfunction and executed an instrument landing system (ILS) approach with the waterline HUD mode evaluated by the flight instructor on a scale of 1 to 5. RESULTS: Ventilation increased during normobaric hypoxia (NH) from 12 L · min -1 to 19 L · min -1 at S p o₂ 75% with 6% O₂, and from 12 L · min -1 to 26 L · min -1 at S p o₂ 77% with 6% O₂ + 4% CO₂. ILS flight performance was similar 10 min after combined hyperventilation and hypoxia (3.1 with 6% O₂ + 4% CO₂ and 3.2 with 6% O₂). No adverse effects were reported during the 24-h follow-up. DISCUSSION: Hyperventilation-provoking normobaric hypoxia training is a new and well-tolerated method to meet NATO Standardization Agreement hypoxia training requirements. Leinonen AM, Varis NO, Kokki HJ, Leino TK. A new method for combined hyperventilation and hypoxia training in a tactical fighter simulator . Aerosp Med Hum Perform. 2022; 93(9):681-687.

Introduction: In military aviation during high-altitude operations, an oxygen or cabin pressure emergency can impair brain function and performance. There are variations in individuals' physiological responses to low partial pressure of oxygen and hypoxia symptoms can vary from one exposure to another. The aim of this study was to evaluate how normobaric hypoxia (NH) affects pilots' minute ventilation and 10 min afterwards on Instrument Landing System (ILS) flight performance in Hawk simulator during a tactical flight sortie. Methods: Fifteen volunteer fighter pilots from the Finnish Air Force participated in this double blinded, placebo controlled and randomized study. The subjects performed three flights in a tactical Hawk simulator in a randomized order with full flight gear, regulators and masks on. In the middle of the flight without the subjects' knowledge, 21% (control), 8% or 6% oxygen in nitrogen was turned on. Minute ventilation (VE) was measured before, during NH and after NH. Forehead peripheral oxygen saturation (SpO 2 ), wireless ECG and subjective symptoms were documented. The flights were conducted so that both subjects and flight instructors were blinded to the gas mixture. The pilots performed tactical maneuvers at simulated altitude of 20,000 ft or 26,000 ft until they recognized the symptoms of hypoxia. Thereafter they performed hypoxia emergency procedures with 100% oxygen and returned to base (RTB). During the ILS approach, flight performance was evaluated. Results: The mean VE increased during NH from 12.9 L/min (21% O2 on the control flight) to 17.8 L/min with 8% oxygen ( p < 0.01), and to 21.0 L/min with 6% oxygen ( p < 0.01). Ten minutes after combined hyperventilation and hypoxia, the ILS flight performance decreased from 4.4 (control flight) to 4.0 with 8% oxygen ( p = 0.16) and to 3.2 with 6% oxygen ( p < 0.01). A significant correlation (r = -0.472) was found between the subjects' VE during 6% oxygen exposure and the ILS flight performance. Discussion: Hyperventilation during NH has a long-lasting and dose-dependent effect on the pilot's ILS flight performance, even though the hypoxia emergency procedures are executed 10 min earlier. Hyperventilation leads to body loss of carbon dioxide and hypocapnia which may even worsen the hypoxia hangover., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Varis, Leinonen, Parkkola and Leino.)

BACKGROUND: Sinus barotraumas are a common condition in aviation medicine, sometimes compromising flight safety and even permanently grounding aircrew. Considering this and the ever-increasing amount of commercial aviation, a thorough examination is required. METHODS: In this survey study, an anonymous, electronic questionnaire was distributed to commercial aircrew of the three major commercial airlines operating in Finland ( N 3799), covering 93% of the target population (i.e., all commercial aircrew operating in Finland, N 4083). Primary outcomes were self-reported prevalence, clinical characteristics, and health and occupational effects of sinus barotraumas in flight. Secondary outcomes were adjusted odds ratios (OR) for frequency of sinus barotraumas with respect to possible risk factors. RESULTS: Response rate was 47% ( N 1789/3799), with 61% ( N 1088) of the respondents having experienced sinus barotraumas in flight. Of those affected, 59% had used medications, 18% had undergone surgical procedures, and 53% had been on sick leave due to sinus barotraumas (38% during the last year) in flight. Factors associated with sinus barotraumas were female sex [OR, 2.47; 95% confidence interval (CI) 1.354.50] and a high number of upper respiratory tract infections (3 vs. <3 URTIs/yr: OR, 3.61; 95% CI 2.654.93). CONCLUSION: Sinus barotraumas were reported by 61% of commercial aircrew. They caused an increased need for medications, otorhinolaryngology-related surgical procedures, and sickness absence from flight duty. The possible risk factors were female sex and a high number of URTIs/yr. Lindfors OH, Ketola KS, Klockars TK, Leino TK, Sinkkonen ST. Sinus barotraumas in commercial aircrew . Aerosp Med Hum Perform. 2021; 92(11):857-863 .

Altitude hypoxia episodes are increasingly common in military aviation. Hypoxia training is mandatory for fighter pilots, but evidence-based data on the effects of training are scarce. The purpose of this study was to validate the normobaric hypoxia (NH) training effect. Data were collected from 89 pilots from the Finnish Air Force (FINAF). This survey was conducted in a tactical F/A-18C Hornet simulator in two sessions under normobaric conditions, in which the pilots performed flight missions and breathed 21% oxygen (O 2 ) in nitrogen (N 2 ), and blinded to the pilot, the breathing gas was changed to a hypoxic mixture containing either 8, 7 or 6% O 2 in N 2 . The time taken to notice hypoxia symptoms and peripheral capillary O 2 saturation was measured. A mean of 2.4 years after the initial training, pilots recognised their hypoxic symptoms 18 s quicker with 8% O 2 mixture, 20 s quicker with 7% O 2 and 10 s quicker with 6% O 2 . Our data indicate that NH training in a flight simulator helps pilots to recognise hypoxia symptoms earlier, and may, thus, enhance flight safety. Practitioner Summary: We show that hypoxia training enhances pilots' ability to recognise symptoms of acute normobaric hypoxic exposure up to 2.4 years after an initial NH training session. Based on these data, refreshment NH training is nowadays mandatory every 3 years in the FINAF as opposed to the North Atlantic Treaty Organisation (NATO) Standardisation Agreement (STANAG) requirement of 5-year intervals between hypoxia trainings. Abbreviations: O 2 : oxygen; TUC; time of usefull consciousness; SpO 2 : peripheral capillary oxygen saturation; NATO: North Atlantic Treaty Organization; STANAG: stanrdization agreement; HH: hypobaric hypoxia; NH: normobaric hypoxia; FINAF: finnish air force; N 2 : nitrogen; ECG: electrocardiogram; CI: confidence interval; SD: standard deviation.

BACKGROUND: Middle ear (ME) barotraumas are the most common condition in aviation medicine, sometimes seriously compromising flight safety. Considering this and the ever-increasing amount of commercial aviation, a detailed overview is warranted. METHODS: In this survey study, an anonymous, electronic questionnaire was distributed to commercial aircrew of the three major commercial airlines operating in Finland ( N 3799), covering 93% of the target population (i.e., all commercial aircrew operating in Finland, N 4083). Primary outcomes were self-reported prevalence, clinical characteristics, and health and occupational effects of ME barotraumas in flight. Secondary outcomes were adjusted odds ratios (OR) for frequency of ME barotraumas with respect to possible risk factors. RESULTS: Response rate was 47% ( N 1789/3799), with 85% ( N 1516) having experienced ME barotraumas in flight. Of those affected, 60% had used medications, 5% had undergone surgical procedures, and 48% had been on sick leave due to ME barotraumas (40% during the last year). Factors associated with ME barotraumas included a high number of upper respiratory tract infections [3 URTIs/yr vs. 0 URTIs/yr: OR, 9.02; 95% confidence interval (CI) 3.9920.39] and poor subjective performance in Valsalva (occasionally vs. always successful: OR, 7.84; 95% CI 3.9715.51) and Toynbee (occasionally vs. always successful: OR, 9.06; 95% CI 2.6730.78) maneuvers. CONCLUSION: ME barotraumas were reported by 85% of commercial aircrew. They lead to an increased need for medications, otorhinolaryngology-related surgical procedures, and sickness absence from flight duty. Possible risk factors include a high number of URTIs and poor performance in pressure equalization maneuvers. Lindfors OH, Ketola KS, Klockars TK, Leino TK, Sinkkonen ST. Middle ear barotraumas in commercial aircrew. Aerosp Med Hum Perform. 2021; 92(3):182189.

INTRODUCTION: The incidence of hypoxia-like symptoms in military aviators is on the rise. Cases can be related to On-Board Oxygen Generating System (OBOGS) malfunction, air contamination, loss of cabin pressurization, hyperventilation, or a combination of these issues simultaneously. Normobaric hypoxia training in tactical fighter simulations has been conducted in the Finnish Air Force since 2008. This training helps aviators to recognize their individual hypoxia symptoms and refreshes hypoxia emergency procedures in a realistic cockpit. METHODS: A flight mission included three set-ups and a return to base (RTB) after the third set-up. In a tactical Hawk simulator, different concentrations of oxygen were used (8%, 7%, and 6% oxygen in nitrogen) to create normobaric hypoxia exposures. During the RTB, the flight instructor evaluated the subjects' flight performance ( N = 16) in order to estimate cognitive functions after hypoxia. A control flight was evaluated before or after the flight with normobaric hypoxia exposure. RESULTS: Instrumental flight rule performance during RTB decreased significantly from 4.81 to 3.63 after normobaric hypoxia and emergency procedures. Some pilots reported fatigue, headache, memory problems, and cognitive impairment as adverse effects up to 12 h after normobaric hypoxia training. DISCUSSION: Hypoxia has a significant effect on flight performance during RTB, even 10 min after hypoxia emergency procedures. Since 100% oxygen was used as emergency oxygen, as in a real aircraft, the oxygen paradox may decrease flight performance. Hypoxia training in tactical fighter simulations provides an opportunity for pilots to also understand the effects of the "hypoxia hangover" on their flight performance. Varis N, Parkkola KI, Leino TK. Hypoxia hangover and flight performance after normobaric hypoxia exposure in a Hawk simulator . Aerosp Med Hum Perform. 2019; 90(8):720-724.

Background: The present study aimed to find out if possible differences in early military flight career +Gz exposure level could predict permanent flight duty limitations (FDL) due to spinal disorders during a pilot's career., Methods: The study population consisted of 23 pilots flying with Gz limitation (max limitation ranging from +2 Gz to +5 Gz) due to spinal disorders and 50 experienced (+1000 flight hours) symptomless controls flying actively in operative missions in the Finnish Air Force. Data obtained for all subjects included the level of cumulative Gz exposure measured sortie by sortie with fatigue index (FI) recordings and flight hours during the first 5 yr of the pilot's career., Results: The mean (± SD) accumulation of FI in the first 5 yr of flying high-performance aircraft was 8.0 ± 1.8 among the pilots in the FDL group and 7.7 ± 1.7 in the non-FDL group. There was no association between flight duty limitations and early career cumulative +Gz exposure level measured with FI or flight hours., Discussion: According to the present findings, it seems that the amount of cumulative +Gz exposure during the first 5 yr of a military pilot's career is not an individual risk factor for spinal disorders leading to flight duty limitation. Future studies conducted with FI recordings should be addressed to reveal the relationship between the actual level of +Gz exposure and spinal disorders, with a longer follow-up period and larger sample sizes.Honkanen T, Sovelius R, Mäntysaari M, Kyröläinen H, Avela J, Leino TK. +Gz exposure and spinal injury-induced flight duty limitations. Aerosp Med Hum Perform. 2018; 89(6):552-556.

Objective: To illuminate the pathophysiology of acute rhinosinusitis (ARS) with sequential monitoring of inflammatory biomarkers during an ARS episode and to clarify their diagnostic usability in bacterial ARS., Study Design: Inception cohort study with 50 conscripts with ARS., Methods: We collected peripheral blood high-sensitive C-reactive protein (hs-CRP), white blood cell (WBC), procalcitonin, and nasal nitric oxide (nNO) counts at 2 to 3 and 9 to 10 days of symptoms during an ARS episode. We simultaneously gathered various clinical parameters and microbiological samples. Bacterial ARS was confirmed with a positive culture of sinus aspirate., Results: Reciprocal correlations and a significant change in biomarker levels between the two visits suggest that ARS involves a local and systemic inflammatory response that was strongest at 2 to 3 days. High-sensitive CRP and nNO reflected responses best (52% had increased CRP levels at 2-3 days; 66% had decreased nNO levels). White blood cell and procalcitonin counts rarely exceeded the reference range. Increased local and systemic inflammatory response were linked to multiple, adenoviral, or influenza A viral etiology or the detection of bacterial ARS. Local response correlated with imaging findings of wide paranasal sinus involvement and ostiomeatal complex occlusion. At 9 to 10 days, elevated (≥ 11 mg/L) and moderately elevated (≥ 49 mg/L) hs-CRP predicted bacterial ARS well (likelihood ratio [LR]+ 3.3 and LR+ 15.8, respectively), but the sensitivity for both findings remained low., Conclusion: Acute rhinosinusitis (particularly bacterial ARS) involves a local and systemic inflammatory response that is strongest at the beginning of symptoms. Elevated hs-CRP supports the diagnosis of bacterial ARS., Level of Evidence: 4. Laryngoscope, 2016 127:E55-E61, 2017., (© 2016 The American Laryngological, Rhinological and Otological Society, Inc.)

Objectives/hypothesis: To evaluate with imaging the course of acute rhinosinusitis (ARS) and the associations between paranasal imaging results, symptoms, bony anatomic variations, and culture-proven bacterial ARS., Study Design: Inception cohort study with 50 conscripts with ARS., Methods: During a single ARS episode, we collected symptoms daily and took sequential cone-beam computed tomography (CBCT) scans of the paranasal sinuses of the same patients 2 to 3, 5 to 6 and 9 to 10 days after the onset of symptoms. Culture-proven bacterial ARS was verified with maxillary sinus aspiration and bacterial culture at 9 to 10 days., Results: At 2 to 3 days, 38% of the patients had major abnormalities, 42% had minor abnormalities in their paranasal sinuses, and 68% had an occluded ostiomeatal complex (OMC). At 5 to 6 days and 9 to 10 days, these proportions remained essentially the same. At 2 to 3 days, patients with bacterial ARS had slightly higher CBCT scores than those without bacterial ARS. Later, the CBCT and symptom scores gradually increased in patients with bacterial ARS and decreased in those without bacterial ARS. The CBCT and symptom scores had only a weak correlation (rs = 0.36), and anatomic variations were not related to development of bacterial ARS., Conclusions: Paranasal mucosal abnormalities and occlusion of the OMC do not develop gradually during ARS, but are present when symptoms begin and remain fairly constant in most patients both with and without bacterial ARS. This indicates that the spread of the disease process to the paranasal sinuses and obstruction of the OMC may not be etiological factors in the development of bacterial ARS., Level of Evidence: 4 Laryngoscope, 126:1965-1970, 2016., (© 2016 The American Laryngological, Rhinological and Otological Society, Inc.)

Introduction: Radio communication remains important for the delivery of safety-critical information in military aviation. Pilots are exposed to high noise levels. Noise attenuation provided by certain helmets is not sufficient, and resulting noise exposure can deteriorate operational effectiveness and flight safety. A need for hearing protection that enables efficient communication is obvious, especially for fighter and helicopter pilots. One possible solution for this issue is molded communication earplugs (m-CEP). Data about the advantages and disadvantages of m-CEPs are limited., Methods: To determine the usage rates, advantages, disadvantages and pilot opinions about m-CEPs, an anonymous survey study including 31 questions was conducted in fighter, fighter trainer, helicopter, and transport aircraft units of the Finnish Defense Forces., Results: Of the pilots who responded, 136 (93%) had used or tried m-CEPs and 90 (62%) were currently using them. There are many benefits to m-CEPs: they seem to enhance experienced speech intelligibility, since 85% of the pilots who had experience about them reported improved speech intelligibility under difficult hearing conditions, and 93% would recommend them to other pilots. It seems m-CEPs provide equal benefits to pilots with and without current hearing problems. They were also considered better than previously used hearing protectors. Still, problems were common: 82% of the pilots reported m-CEP related drawbacks, of which technical problems and discomfort issues were the most prevalent., Discussion: Most military pilots hold a positive opinion on m-CEPs and are willing to recommend their use. Technical problems and discomfort issues are, however, relatively common.

Objectives/hypothesis: To evaluate the diagnostic accuracy of symptoms, the symptom progression pattern, and clinical signs in identifying bacterial acute rhinosinusitis (ARS)., Study Design: We conducted an inception cohort study among 50 military recruits with ARS., Methods: We collected symptoms daily from the onset of symptoms to approximately 10 days. At 9 to 10 days, standardized data on symptoms and physical findings were gathered. A positive culture of maxillary sinus aspirate was considered to be the reference standard for bacterial ARS., Results: At 9 to 10 days, the presence or deterioration after 5 days of any of the symptoms could not be used to diagnose bacterial ARS. Toothache had an adequate positive likelihood ratio (positive likelihood ratio [LR+] 4.4) but was too rare to be used for screening. In contrast, several physical findings at 9 to 10 days were of more diagnostic use and frequent enough for screening. Moderate or profuse (vs. none/minimal) amount of secretion in nasal passage seen in anterior rhinoscopy satisfactorily either ruled in, if present (LR+ 3.2), or ruled out, if absent (negative likelihood ratio 0.2), bacterial ARS. If any secretion was seen in the posterior pharynx or middle meatus, the probability of bacterial ARS increased markedly (LR+ 5.3 and LR+ 11.0, respectively)., Conclusion: We found symptoms or their change to be of little use in identifying bacterial ARS. In contrast, we observed several clinical findings after 9 to 10 days of symptoms to predict bacterial ARS quite accurately., (© 2015 The American Laryngological, Rhinological and Otological Society, Inc.)

It was explored how three types of intensive cognitive load typical of military aviation (load on situation awareness, information processing, or decision-making) affect speech. The utterances of 13 male military pilots were recorded during simulated combat flights. Articulation rate was calculated from the speech samples, and the first formant (F1) and second formant (F2) were tracked from first-syllable short vowels in pre-defined phoneme environments. Articulation rate was found to correlate negatively (albeit with low coefficients) with loads on situation awareness and decision-making but not with changes in F1 or F2. Changes were seen in the spectrum of the vowels: mean F1 of front vowels usually increased and their mean F2 decreased as a function of cognitive load, and both F1 and F2 of back vowels increased. The strongest associations were seen between the three types of cognitive load and F1 and F2 changes in back vowels. Because fluent and clear radio speech communication is vital to safety in aviation and temporal and spectral changes may affect speech intelligibility, careful use of standard aviation phraseology and training in the production of clear speech during a high level of cognitive load are important measures that diminish the probability of possible misunderstandings., (© 2011 Acoustical Society of America)

Introduction: Despite technological advances in conveying information, speech communication is still a key safety factor in aviation. Effective radio communication is necessary, for example, in building and maintaining good team situation awareness. However, little has been reported concerning the prevalence and nature of radio communication problems in everyday working environments in military aviation., Methods: We surveyed Finnish Defense Forces pilots regarding the prevalence of radio speech communication problems., Results: Of the 225 pilots contacted, 75% replied to our survey. Altogether 138 of the respondents were fixed-wing pilots and 31 were helicopter pilots. Problems in radio communication occurred, on average, during 14% of flight time. The most prevalent problems were multiple speakers on the same radio frequency band causing overlapping speech, missing acknowledgments, high background noise especially during helicopter operations, and technical problems. Of the respondents, 18% (31 pilots) reported having encountered at least one potentially dangerous event caused by problems in radio communication during their military aviation career. If the employer were to offer extra hearing protection, such as custom-made ear plugs, 93% of the pilots indicated that they would use it., Discussion: Communication can be a flight safety factor especially during intense air combat exercises and other information-loaded flights. During these situations, communication should be clear and focused on the most essential information. So, training and technical improvements are necessary for better communication. High quality radio speech communication also improves operational effectiveness in military aviation.

Caffeine has been suggested to act as a countermeasure against fatigue in military operations. In this randomized, double-blind, placebo-controlled study, the effect of caffeine on simulator flight performance was examined in 13 military pilots during 37 hours of sleep deprivation. Each subject performed a flight mission in simulator four times. The subjects received either a placebo (six subjects) or 200 mg of caffeine (seven subjects) 1 hour before the simulated flights. A moderate 200 mg intake of caffeine was associated with higher axillary temperatures, but it did not affect subjectively assessed sleepiness. Flight performance was similar in both groups during the four rounds flown under sleep deprivation. However, subjective evaluation of overall flight performance in the caffeine group tended to be too optimistic, indicating a potential flight safety problem. Based on our results, we do not recommend using caffeine pills in military flight operations.

Introduction: The psychological workload of flying has been shown to increase heart rate (HR) during flight simulator operation. The association between HR changes and flight performance remains unclear., Methods: There were 15 pilots who performed a combat flight mission in a Weapons Tactics Trainer simulator of an F-18 Hornet. An electrocardiogram (ECG) was recorded, and individual incremental heart rates (deltaHR) from the HR during rest were calculated for each flight phase and used in statistical analyses. The combat flight period was divided into 13 phases, which were evaluated on a scale of 1 to 5 by the flight instructor., Results: HR increased during interceptions (from a mean resting level of 79.0 to mean value of 96.7 bpm in one of the interception flight phases) and decreased during the return to base and slightly increased during the ILS approach and landing. DeltaHR appeared to be similar among experienced and less experienced pilots. DeltaHR responses during the flight phases did not correlate with simulator flight performance scores. Overall simulator flight performance correlated statistically significantly (r = 0.50) with the F-18 Hornet flight experience., Conclusions: HR reflected the amount of cognitive load during the simulated flight. Hence, HR analysis can be used in the evaluation of the psychological workload of military simulator flight phases. However, more detailed flight performance evaluation methods are needed for this kind of complex flight simulation to replace the traditional but rough interval scales. Use of a visual analog scale by the flight instructors is suggested for simulator flight performance evaluation.

Background: Serum protein S100B determinations have been recently suggested as markers of traumatic brain injury. However, little is known about the effects of extracranial injuries on S100B levels in trauma patients., Methods: We studied 224 patients with head trauma (54 of whom also had extracranial injuries), 155 patients with various types of extracranial injuries, and 8 healthy pilots exposed to high Gz forces. The head trauma patients had either no brain injury (n = 35), mild brain injury (n = 165), or moderate to severe brain injury (n = 24). The extracranial injuries were divided into small and large injuries. Serum protein S100B levels were determined from samples taken within 6 hours after the trauma event., Results: The head trauma patients had a significantly higher median S100B (0.17 microg/L) than the patients with extracranial injuries (0.07 microg/L) (p < 0.001). Serum S100B levels also correlated with the severity of brain injury (p < 0.001), the highest values occurring in the patients with moderate to severe brain injury (1.27 microg/L). However, large extracranial injuries also elevated S100B levels (0.35 microg/L), whereas small extracranial injuries in the absence of head trauma did not significantly affect S100B levels (0.07 microg/L). Above the cutoff level of 0.13 microg/L, there were 61% of the head trauma patients and 26% of those with extracranial injuries (Pearson chi test, p < 0.001). However, only 4% of the patients with purely extracranial injuries had a concentration of S100B above the cutoff level of 0.50 microg/L, whereas the head trauma patients with moderate to severe brain injury exceeded this cutoff in 67% of the cases. Exposure to high Gz forces did not influence serum S100B levels in healthy individuals., Conclusion: We conclude that serum S100B is a sensitive marker of brain injury, which correlates with the severity of the injury. Large extracranial injuries also elevate S100B levels. However, S100B has a high negative predictive power, and the finding of a normal S100B value shortly after trauma should thus exclude significant brain injury with a high accuracy.

Introduction: Positive pressure breathing for G-protection (PBG) reduces the need for fighter pilots to use the fatiguing anti-G straining maneuver (AGSM) so that they can better endure high acceleration (+Gz). The aim of the study was to determine the differences in cerebral blood flow during flight with an extended-coverage anti-G suit (ECGS) with AGSM or with PBG., Methods: Subjects were eight male members of the Finnish Air Force. Each was studied in the laboratory at +1 Gz and then during two identical flights in the back seat of the BAe Hawk Mk 51 jet trainer at +6 Gz, first with AGSM and second with PBG (24 mmHg). Regional cerebral blood flow (rCBF) was measured by injecting (99 m) Tc-ECD for deposition at +6 Gz, then scanning the subject in the laboratory an hour later using single photon emission computed tomography (SPECT)., Result: The rCBF was 30% below baseline for both the AGSM and PBG., Conclusions: PBG maintained CBF at +6 Gz without the need for the fatiguing AGSM.

Background: Information processing and stress tolerance are necessary features for instrument flying (IFR), especially among student pilots. Psychological workload of IFR flight may lead to stress reactions such as neuroendocrine activity., Methods: Neuroendocrine responses to an IFR flight with Vinka piston-engined primary trainer were studied in 35 male volunteers who participated in the basic military flying course of the Finnish Air Force (FAF). The student pilots performed a 40-min IFR flight mission and a control session on land in randomized order between 11.00 h and 15.00 h. The IFR flight included 3 NDB approaches and was evaluated by flight instructors. Blood samples were collected 15 min before, 5 min and 60 min after the flight as well as control session, and. Plasma ACTH, beta3-endorphin (BE), cortisol, prolactin, adrenaline (A) and noradrenaline (NA) were measured. Psychological evaluations included psychomotor test (Wiener), Multi Coordination and Attention Test, ability tests and personality tests (CMPS and 16 PF). The overall psychological evaluation was made by an aviation psychologist., Results: Plasma ACTH was significantly higher before and 5 min after the flight compared with control levels, but plasma BE increased significantly only before the flight. Plasma cortisol was significantly elevated before and 5 min after the flight. Plasma prolactin, NA and A increases were significant 5 min after the flight. High A levels after the flight correlated significantly with poor IFR flight performance as well as with poor psychomotor test results., Conclusions: The plasma prolactin and NA increases after the flight represented a direct type of stress reaction to the flight situation. The plasma BE response to IFR flight was an anticipatory stress reaction, but plasma ACTH, cortisol and A responses included both anticipatory and direct types of stress reactions. Psychological factors, flight performance and neuroendocrine responses to IFR flight appear to be associated with each other. Therefore, neuroendocrine reactions as a response to the psychological workload of military flying could be used for identifying stress tolerance in military pilots.

Background: Military flying sets high demands on the mental performance and stress tolerance of pilots. Neuroendocrine responses could be a method for evaluating stress tolerance., Methods: Psychological workload and neuroendocrine responses associated with the psychomotor Wiener's test were studied in 80 male volunteers. These personnel had applied for the basic military flying program of the Finnish Air Force (FAF). After the first blood sample at 0930 h, the subjects were randomly assigned to test (n = 40) and control groups (n = 40). The test group performed the psychomotor test, which lasted 10 min. The second blood sample was collected 1 min after the test. The control group was clinically examined and the blood sample was taken in the same way., Results: A high plasma ACTH level before the psychomotor test predicted (r = 0.36, p = 0.02) a poor overall result in the psychomotor test. After the psychomotor test, plasma adrenocorticotropin (ACTH) and beta-endorphin levels were significantly higher than before the test. They were also higher than in the control group. Plasma cortisol and prolactin levels increased after the psychomotor test, but the increase was not statistically significant. High ACTH, cortisol and prolactin increments were specific to a high amount of delayed (over 2 s) psychomotor responses, as a marker of information overload., Conclusions: Elevated plasma ACTH, cortisol and prolactin levels, after the psychomotor test, were associated with a high amount of the delayed responses. This indicates that high neuroendocrine responses were connected with problems in stress tolerance during information processing. High neuroendocrine reactions under information load could, therefore, be used for identification of lowered stress tolerance.

Methods: To investigate the influence that psychological workload, associated with simulated combat military flight, has on secretion of stress hormones we measured concentrations of plasma corticotropin-releasing hormone (CRH), pro-opiomelanocortin (POMC) related adrenocorticotropin (ACTH), beta-endorphin (BE), and cortisol in 10 Finnish Air Force (FAF) military interceptor pilots. They performed the same 20-min combat flight mission in a Saab J35 Draken S simulator, including four radar attacks during one-on-one situations with increasing cognitive tasks and psychological strain. Blood samples were collected -35 min, 1 min, 30 min and 60 min after the flight mission. Control blood samples were collected from the subjects at the same time of day in randomized order before or after the flight mission. During the control period the subjects were allowed to perform ground duties., Results: Plasma CRH was undetectable in samples drawn before or after the flight and control period. Plasma ACTH was significantly (p < 0.05) elevated before the simulated combat flight when compared with the respective value in the control experiment. This is an anticipatory type of stress reaction. Plasma BE did not change significantly after the simulated flight. Plasma cortisol increased significantly (p < 0.05) 1 min after the simulated flight. One of the ten pilots had an extreme POMC and cortisol activation after the flight mission, suggesting that the pilot's stress tolerance was less than average., Conclusions: We conclude that stress, produced during simulated combat military flight, increases POMC and cortisol secretion. An anticipatory-type stress reaction was found to be associated with the simulated combat flight, as judged from the increased preflight plasma ACTH.