Simulated parachute descent in the cold: thermal responses and manual performance.

BACKGROUND: Ejection from a fighter aircraft can expose the pilot to extreme cold and windy conditions. Knowledge of the effects of such conditions on thermal responses and performance of the pilot is scarce. HYPOTHESIS: It is expected that the temperature of bare skin and fingers may decrease to the level where health and/or performance are hampered. METHODS: Seven fighter pilots performed a simulated parachute descent (SPD) at ambient temperature (Ta) of -35 degrees C and wind velocity of 10 m x s(-1). The 8-min SPD was followed by a 60-min cold exposure (CE) at Ta of -20 degrees C. Flight garments with or without immersion suit were used. During SPD the subjects performed basic survival tasks. Rectal and skin temperatures were measured and manual performance was tested. RESULTS: Thermal responses did not significantly differ between the clothing ensembles. Mean skin temperature was 28 degrees C and 27 degrees C at the end of SPD and CE, respectively. The cheek temperature was 9 degrees C (range 3.2-13.8 degrees C) at the end of SPD. Finger skin temperature was 7 degrees C and 9 degrees C at the end of SPD and CE, respectively. The subjects could perform the defined tasks during SPD while manual performance was slightly impaired during CE. CONCLUSIONS: Subjects could tolerate the 8-min SPD and the following CE in the studied conditions without a loss of vital performance in basic survival actions. However, the risk of frostbite on the uncovered skin area as well as numbness of the fingers may jeopardize pilots' health and performance during parachuting.

Active noise reduction in aviation helmets during a military jet trainer test flight.

Cockpit noise measurements were carried out in a two-seat jet trainer. For the continuous time and frequency analyses a two-channel tape-recording system was constructed of two miniature microphones connected through an amplifier to a digital tape-recorder. The analysed and averaged noise exposure including radio communication was 80-81 dB when the ANC system was on and 84-89 dB when the ANC system was off. For the conventional flight helmet the same noise exposure was 86 dB, and the noise exposure in the cockpit was 104-106 dB. The effect of the ANC system on the averaged noise exposure (L(Aeq8min)) was an improvement of 4-8 dB over the noise attenuation of the same helmets when the ANC system was off. Both ANC systems worked properly during the test flights. No severe ringing or voice circulation was found except during extreme vibration.

An outbreak of respiratory diseases among workers at a water-damaged building--a case report.

We describe a military hospital building with severe, repeated and enduring water and mold damage, and the symptoms and diseases found among 14 persons who were employed at the building. The exposure of the employees was evaluated by measuring the serum immunoglobulin G (IgG)-antibodies against eight spieces of mold and yeast common in Finnish water and mold damaged buildings and by sampling airborne viable microbes within the hospital. The most abundant spieces was Sporobolomyces salmonicolor. All but one of the employees reported some building-related symptoms, the most common being a cough which was reported by nine subjects. Four new cases of asthma, confirmed by S. salmonicolor inhalation provocation tests, one of whom was also found to have alveolitis, were found among the hospital personnel. In addition, seven other workers with newly diagnosed rhinitis reacted positively in nasal S. salmonicolor provocation tests. Skin prick tests by Sporobolomyces were negative among all 14 workers. Exposure of the workers to mold and yeast in the indoor air caused an outbreak of occupational diseases, including asthma, rhinitis and alveolitis. The diseases were not immunoglobulin E (IgE)-mediated but might have been borne by some other, as yet unexplained, mechanism.

Comparison of commercial solid-phase extraction sorbents for the sample preparation of potato glycoalkaloids.

In this study five different commercial sorbents C18, SCX, CN, Certify and Oasis HLB were compared for the solid-phase extraction of potato glycoalkaloids. The recoveries were determined using alpha-solanine, alpha-chaconine and alpha-tomatine, which contained dehydrotomatine as an impurity, as standard compounds. The samples were analysed by reversed-phase liquid chromatography under gradient elution conditions using a Zorbax Rx-C18 column and acetonitrile-25 mM triethylammonium phosphate buffer (pH 3.0) as the mobile phase. The highest recovery (approximately 100%) was achieved with Oasis HLB (60 mg) cartridges. An acetic acid extract of wild Solanum brevidens leaf material was used for the testing of a clean-up procedure. The SCX proved to be the most selective and efficient for removing the undesired components from the leaf extract.

Determination of solanidine- and tomatidine-type glycoalkaloid aglycons by gas Chromatography/Mass spectrometry.

A combined derivatization method for gas chromatographic/mass spectrometric (GC/MS) analysis of steroidal glycoalkaloid (SGA) aglycons was developed using both trimethylsilylation and pentafluoropropionylation. In comparison with underivatized or only silylated aglycons, the new technique produces more specific and abundant fragmentation for compounds with a tomatidine-type structure. For example, the difference between solasodine and tomatidine, the former containing a double bond at position 5,6 in the steroidal skeleton, can be observed by their base peak fragments at m/z 417 (C(24)H(41)O(2)Si(2)) and m/z 419 (C(24)H(43)O(2)Si(2)). The method is well suited for the simultaneous determination of both solanidane- and spirosolane-type SGA aglycons from Solanum species and hybrids. The reproducibility of the method, including SGA extraction, hydrolysis, derivatization, and quantitative GC/MS analysis, was <6% (CV) for the principal aglycons determined from a hybrid between a wild potato species, Solanum brevidens Phil., and a cultivated potato, S. tuberosum L. A single ion monitoring technique using specific fragments m/z 419 and 417 could be applied for the determination of minor stereoisomers, which are often overlapped by large amounts of tomatidine.

Reversed-phase liquid chromatographic separation and simultaneous profiling of steroidal glycoalkaloids and their aglycones.

Improved and simplified reversed-phase liquid chromatographic conditions for the separation and simultaneous profiling of both steroidal glycoalkaloids and their aglycones, having solanidane- or spirosolane-type structures, are described. The most reproducible retention behavior for these ionizable compounds on C18 columns was achieved under isocratic and gradient elution conditions using acetonitrile in combination with triethylammonium phosphate buffer at pH 3.0, when basic functional groups of solutes and silanol groups on the silica are fully protonated minimizing ionic interactions. Gradient elution was the only feasible approach for the simultaneous separation of steroidal glycoalkaloids and their aglycones. A Zorbax SB C18 column, specially designed for low-pH separations, showed good performance in critical separations. The impurities of the commercial tomatine and tomatidine standards were studied and confirmed using mass spectrometric, liquid chromatographic and thin-layer chromatographic methods.

Low-altitude overflights of fighters and the risk of hearing loss.

BACKGROUND AND OBJECTIVE: Much data are available on noise properties which cause hearing loss. There are not, however, reports on the effects of low-altitude overflight noise on the permanent threshold shift (PTS). METHODS: Low-altitude overflight noise generated by the Finnish Air Force's jet fighters and an advanced jet trainer was measured with flight distances varying from 50-310 m from the measurement point. The aircraft were always subsonic, velocities being usually 0.9 Mach or less. The measurements were undertaken because of two claims for the compensation of hearing loss caused by overflights of jet fighters on cross-country training missions. RESULTS: Peak noise levels (LCpeak) varied from 109-150 dB depending on aircraft type and the use of afterburner. The 1-s single A-weighted exposure levels (ASEL) during these overflights were 95-135 dB which correspond to daily (8 h) exposure levels of 50-90 dB. CONCLUSIONS: According to these results and the principles of noise evaluation, there should be no risk of permanent hearing loss when the distance to an overflying jet fighter is more than 200 m. However, we have received two claims, and the audiometric analyses of two subjects who had suffered hearing loss in one ear in Finland during the 1990s may indicate that there is very likely a connection between the incidents and the hearing losses.

Muscle fatigue caused by repeated aerial combat maneuvering exercises.

BACKGROUND: Little is known about the development of in-flight muscular fatigue during repeated flights. HYPOTHESIS: This study was conducted to evaluate muscular fatigue in different upper body and neck muscles during repeated aerial combat maneuvering exercises. METHODS: Six pilots volunteered as test subjects. They performed one-to-one dog fight exercise three times (1 pilot, four times) in one day. During the flights, the pilots' electromyographic activity (EMG) was measured from the abdomen, back, neck and lateral neck. The mean muscular strain for each muscle was calculated. Before the first flight and after each flight, the maximal isometric strength of each muscle was measured. RESULTS: The results showed that maximal isometric strength between the first and last measurement decreased in the back, neck (p < 0.05) and lateral neck muscles. While the G-stress remained the same, the muscular strain during exercises increased in every muscle, but was significant only in neck and lateral neck (p < 0.05-0.01). Due to these changes, the fatigue index in the neck and lateral neck muscles was 2.0-2.1, and 1.3-1.4 (1.0 = no fatigue) in the abdomen and back muscles. CONCLUSIONS: Repeated aerial combat maneuvering exercises caused fatigue in every muscle studied. The fatigue was greater in the neck area, which may increase the risk for neck injuries, and may reduce mission effectiveness. The fighter pilots' muscular strength and endurance in the neck area are subjected to very high demands, especially if exercises are repeated several times. The recovery of the neck muscles from fatigue after repetitive exercises should receive special attention.

Neuroendocrine responses and psychomotor test results in subjects participating in military pilot selection.

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.

Neuroendocrine responses to psychological workload of instrument flying in student pilots.

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.

+Gz associated stenosis of the cervical spinal canal in fighter pilots.

Previous magnetic resonance imaging (MRI) studies have shown that repeated exposure to +Gz forces can cause premature degenerative changes of the cervical spine (i.e. a work-related disease). This paper reports on two clinical cases of +Gz-associated degenerative cervical spinal stenosis caused by dorsal osteophytes in fighter pilots. Conventional x-rays and MRI were used to demonstrate narrowing of the cervical spinal canal. The first case was complicated by a C6-7 intervertebral disk prolapse and a congenitally narrow spinal canal. The second case involved progressive degenerative spinal stenosis in the C5-6 disk space which required surgery. The findings in this case were confirmed by surgery which showed posterior osteophytes and thickened ligaments compressing the cervical medulla. These two cases suggest that +Gz forces can cause degenerative spinal stenosis of the cervical spine. Flight safety may be jeopardized if symptoms and signs of medullar compression occur during high +Gz stress. It is recommended that student fighter pilots undergo conventional x-rays and MRI studies in order to screen out and reject candidates with a congenitally narrow spinal canal. These examination methods might be useful in fighter pilots' periodic medical check-ups in order to reveal acquired degenerative spinal stenosis.

Reversed-phase high-performance liquid chromatographic screening method for serum steroids using retention index and diode-array detection.

A multisteroid screening method has been developed based on the use of 1-[4-(2,3-dihydroxypropoxy)phenyl]-1-alkanones as retention index standards and UV absorbance spectra recorded on-line with a diode-array detector using reversed-phase high-performance liquid chromatographic gradient elution with acetonitrile and water. The effect of chromatographic conditions on retention indices of steroids were studied. The method was tentatively applied to profiling of steroids in serum samples.

Pro-opiomelanocortin activation and simulated interceptor combat flight.

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.

Heart rate responses to real and simulated BA Hawk MK 51 flight.

BACKGROUND: The effects of psychological workload on inflight heart rate were studied in five experienced (flight instructors) and five less experienced (cadets) military pilots of the Finnish Air Force (FAF). METHOD: The subjects performed the same flight mission twice; first with the BA Hawk MK 51 simulator with minimal G-forces and after that with the BA Hawk MK 51 jet trainer with Gz-forces below +2. The mission included: a) 2 min rest after seating; b) take-off; c) ILS approach in the minimum weather conditions (initial, intermediate and final approach); d) landing tour (visual approach); and e) landing. The heart rates were continuously measured using a small portable recorder developed at the University of Jyväskylä, Finland. The R-R intervals were stored and analyzed with an accuracy of 1 ms. The different phases of each flight were marked in the data by using codes given beforehand for each critical event. RESULTS: The take-off resulted in a significant increase in the heart rate from the resting levels both in the cadets and the flight instructors in both planes. In the simulator the heart rate decreased during the initial approach and slightly increased after it during the intermediate approach. Thereafter the heart rate decreased during the landing tour which seemed to be the least psychologically demanding phase of the simulated flight. The heart rate increased again during the landing but did not exceed the heart rates measured during the take-off and the ILS-approach. There were no statistical differences between the groups. In the jet trainer no decrease in the heart rate could be observed immediately after the take-off, unlike in the case of the simulated flight. The inflight heart rate increased during the final approach, decreased during the landing tour and finally increased during the landing. According to the heart rate analysis the final approach was the most loaded phase of the real flight. The changes towards the phases of final approach and landing were greater among the flight instructors. CONCLUSION: There were no statistically significant differences between the mean heart rates during the real and the simulated flight. It is suggested that the heart rate changes for most reflected the changes in cognitive workload.

Muscle strain during aerial combat maneuvering exercise.

BACKGROUND: Little is known about the in-flight muscular strain of fighter pilots. HYPOTHESIS: The purpose of this study was to measure fighter pilots' mean and peak muscular strain during aerial combat maneuvering exercises. The results obtained were compared against existing ergonomic recommendations. METHODS: Six pilots volunteered to serve as test subjects. Their mean age (+/- SD) was 28.5 +/- 5 yr, height 181 +/- 7 cm, and weight 75 +/- 10 kg. They performed one-to-one dog-fight exercises in the morning and in the afternoon. During the flights, the pilots' electromyographic activity (EMC) was measured from the thigh, abdomen, back, and lateral neck. The mean and peak muscular strain for each muscle was calculated as the percentage of maximal voluntary contraction (%MVC). RESULTS: The results showed that the mean muscular strain was 5.2-19.8% MVC, the strain in the lateral neck being the highest. Peak muscular strain (over 50% MVC) occurred almost only during the encounters and usually in the lateral neck. Other muscles were subjected to fewer peak strain episodes; most of these occurred in the back. At least one peak strain episode exceeding 100% MVC was recorded for every muscle studied. The highest peak strain 257% MVC, was measured in the lateral neck. This peak strain episode caused an injury to the lateral neck area, and the flight mission was discontinued. CONCLUSIONS: The mean muscular strain measured in this study was rather low. However, the strain occurring in the lateral neck and the back exceeds the ergonomic recommendations for static work. Especially in the lateral neck, and to some extent in the back, peak strain occurs frequently, in a magnitude that is well above the maximal voluntary contraction; in these areas, the peak strain presents a potential risk of injury and negative health effects. The level and frequent occurrence of peak strain episodes means that fighter pilots' muscular strength and muscular endurance, especially in the neck and shoulder area, are subjected to demands clearly higher than those of the average population.

Spinal shrinkage due to +Gz forces.

BACKGROUND: Fighter pilots frequently complain of inflight pain in the cervical or lumbar spine. As to the cervical spine, there is evidence that repeated exposures to high +Gz forces and inflight neck pain may cause premature cervical disk degeneration. Whether inflight lumbar pain caused by high +Gz forces has a similar effect on the lumbar spine has not been studied. HYPOTHESIS: The aim of the study was to investigate whether high +Gz forces during aerial combat maneuvering reduces the body height. Investigation to determine whether any long-term degenerative changes occur in the lumbar spine was beyond the scope of this study. METHODS: The body height of 20 junior fighter pilots was measured before and after 30 min of recumbent rest and after high-G flights. A special measuring device was used. Measurements were also made with the pilots sitting fully equipped in a fighter aircraft on the ground. RESULTS: Maneuvering under high +Gz forces for 40 min caused a 4.9 mm decrease in body height. Recumbent rest before flights increased body height by 2.5-3.5 mm, and sitting in an aircraft returned body height to the values measured before rest. CONCLUSIONS: The findings indicate that +Gz forces place a high stress on the spinal column. Therefore, the work of a fighter pilot can be considered to be physically demanding with respect to the spinal column.

Neuroendocrine responses to real and simulated BA Hawk MK 51 flight.

The effects of psychological workload on the plasma levels of eight neuroendocrine hormones were studied in 5 undergraduate and 5 senior military pilots of the Finnish Air Force (FAF). All subjects performed the same short-term basic flight mission, which included the following: 1) start; 2) ILS-approach in minimum weather conditions; 3) visual approach; and 4) landing. The mission was performed twice: first with the BA Hawk MK 51 simulator with minimal G-forces and after that with a BA Hawk MK 51 jet trainer with Gz-forces below +2. Blood samples were collected 30 min before and 10 min after the mission and were measured for adrenaline, noradrenaline, ACTH, beta-endorphin, prolactin, vasopressin (AVP), atrial natriuretic peptide (ANP), and cortisol. The plasma levels of adrenaline, noradrenaline, ACTH, beta-endorphin, and cortisol did not change significantly in response to simulated or real flight. Plasma prolactin levels increased significantly (p = 0.037) in all subjects after the mission performed with jet trainer, and the increase was especially great in cadets. However, the same mission performed with the simulator did not raise plasma prolactin levels. This finding suggests that the psychological workload in a flight simulator does not correspond to the psychological workload in a real jet trainer, at least not in basic flying. Plasma AVP increased significantly (p = 0.032) after the mission performed with the simulator in cadets; this increase can be described as a "first-time effect." Plasma ANP also increased significantly (p < 0.05) after a real jet trainer flight.(ABSTRACT TRUNCATED AT 250 WORDS)

Perceived exertion during submaximal G exposures before and after physical training.

Ratings of perceived exertion (RPE) were registered at submaximal levels in G endurance tests of a combined strength and endurance training program in 17 pilots. After 12 months of physical training, the endurance G tolerance (time to exhaustion during simulated aerial combat maneuver), increased by a mean of 40% (p < 0.001), while the mean RPE at 5 min submaximal G exposure decreased by 1.2 units (p < 0.02). Following 12 months of physical training, a significant relationship was observed between the improvement of the endurance G tolerance and the decrease of the RPE at 5 min (p = 0.05). Mean SaO2 at 5 min increased from 84 to 90% (p < 0.01) after training, while heart rate responses to G stress did not change. It is concluded that mean RPE and, to some extent, mean SaO2 during submaximal G exposures may be used as indicators of shifts in endurance G tolerance. The procedure may reduce the need for exhaustive G tolerance tests with associated risks and discomfort.

Cervical disk bulges in fighter pilots.

This paper reports three cases of bulging cervical disks among fighter pilots flying high-performance aircraft who experienced acute in-flight neck pain during aerial combat maneuvers under high +Gz forces. Radiographic investigations (magnetic resonance imaging/computed tomography/myelography) revealed that disk bulges were the cause of the pain. One pilot underwent decompressive surgery, and two were treated conservatively. Acute in-flight neck pain and related problems, such as bulging cervical disks, may become more common, since the modern fighter aircraft of the future will be better able to create and sustain high +Gz forces than the fighter aircraft in use today. Further, the increasing number of helmet-mounted devices will make flight helmets heavier, thus placing increased stress on cervical structures.

High-performance liquid chromatographic screening method for mycotoxins using new retention indexes and diode array detection.

A reversed-phase high-performance liquid chromatographic (RP-HPLC) screening method for the determination of mycotoxins has been developed. The toxins were characterized by retention indexes and on-line UV spectra produced with a diode array detector (DAD). Retention indexes of mycotoxins exhibiting a wide range of polarities and chemical structures were determined during linear gradient elution with an acetonitrile/water solvent system. The retention index scale was based on the use of a new homologous series of 1-[4-(2,3-dihydroxypropoxy)phenyl]-1-alkanones (D-compounds) as internal standards. The mycotoxins studied were: five trichothecenes of group A: T-2 toxin (T-2), HT-2 toxin (HT-2), diacetoxyscirpenol (DAS), neosolaniol (NEO), and an isomer of neosolaniol (NEO isomer); three trichothecenes of group B: nivalenol (NIV), deoxynivalenol (DON), and fusarenon-X (FUS-X); four aflatoxins: B1, B2, G1, and G2; and five other mycotoxins: sterigmatocystin (STE), zearalenone (ZEA), ochratoxin A (OCH A), citrinin (CIT), and patulin (PAT).