Siitonen SL, Kauppinen T, Leino TK, Vanninen E, Kuronen P, Länsimies E. Cerebral blood flow during acceleration in flight measured with SPECT. Aviat Space Environ Med 2003; 74:201–6. 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). Results: 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.

Yoshida N, Sairyo K, Sasa T, Fukunaga M, Koga K, Ikata T, Yasui N. Electrical stimulation prevents deterioration of the oxidative capacity of disuse-atrophied muscles in rats. Aviat Space Environ Med 2003; 74:207–11. Introduction: The purpose of this study was to evaluate the effects of electrical stimulation on disuse-atrophied muscles. Methods: Sprague-Dawley rats were used and divided into three groups: control (C), hind-limb suspended for 7 d (HS), and HS plus transcutaneous electrical stimulation for 7 d (ES). In the ES group, transcutaneous electrical stimulation was induced at 1 Hz for 1 h every day to condition the gastrocnemius-plantaris-soleus muscles. Muscle oxidative capacity was evaluated by ³¹P-MRS in vivo. Maximum tension and muscle wet mass were also measured. Results: Muscle oxidative capacity decreased within 1 wk in HS; however, it was maintained when electric stimulation was applied to the suspended limb. The maximum twitch tension in HS was significantly smaller than that in C (p < 0.05), while in ES it did not differ from that in C. The muscle mass was significantly smaller in the HS and ES groups compared to C (p < 0.05). Conclusion: These data indicated that twitch electrical stimulation was effective in preventing deterioration of muscle functions, such as maximum tension and oxidative capacity, induced by 1 wk of disuse.

Convertino VA, Ratliff DA, Doerr DF, Ludwig DA, Muniz GW, Benedetti E, Chavarria J, Koreen S, Nguyen C, Wang J. Effects of repeated Valsalva maneuver straining on cardiac and vasoconstrictive baroreflex responses. Aviat Space Environ Med 2003; 74:212–9 Introduction: We hypothesized that repeated respiratory straining maneuvers (repeated SM) designed to elevate arterial BPs (arterial baroreceptor loading) would acutely increase baroreflex responses. Methods: We tested this hypothesis by measuring cardiac baroreflex responses to carotid baroreceptor stimulation (neck pressures), and changes in heart rate and diastolic BP after reductions in BP induced by a 15-s Valsalva maneuver in 10 female and 10 male subjects at 1, 3, 6, and 24 h after performing repeated SM. Baroreflex responses were also measured in each subject at 1, 3, 6, and 24 h at the same time on a separate day without repeated SM (control) in a randomized, counterbalanced cross-over experimental design. Results: There was no statistical difference in carotid-cardiac and peripheral vascular baroreflex responses measured across time following repeated SM compared with the control condition. Integrated cardiac baroreflex response (ΔHR/ΔSBP) measured during performance of a Valsalva maneuver was increased by approximately 50% to 1.1 ± 0.2 bpm · mm Hg⁻¹ at 1 h and 1.0 ± 0.1 bpm · mm Hg⁻¹ at 3 h following repeated SM compared with the control condition (0.7 ± 0.1 bpm · mm Hg⁻¹ at both 1 and 3 h, respectively). However, integrated cardiac baroreflex response after repeated SM returned to control levels at 6 and 24 h after training. These responses did not differ between men and women. Conclusions: Our results are consistent with the notion that arterial baroreceptor loading induced by repeated SM increased aortic, but not carotid, cardiac baroreflex responses for as long as 3 h after repeated SM. We conclude that repeated SM increases cardiac baroreflex responsiveness which may provide patients, astronauts, and high-performance aircraft pilots with protection from development of orthostatic hypotension.

Golding JF, Bles W, Bos JE, Haynes T, Gresty MA. Motion sickness and tilts of the inertial force environment: active suspension systems vs. active passengers. Aviat Space Environ Med 2003; 74:220–7. Background: Maneuvering in vehicles exposes occupants to low frequency forces (<1 Hz) which can provoke motion sickness. Hypothesis: Aligning with the tilting inertial resultant (gravity + imposed horizontal acceleration: gravito-inertial force (GIF)) may reduce motion sickness when tilting is either ‘active’ (self-initiated; Experiment 1) or ‘passive’ (suspension machinery; Experiment 2). Methods: Exp 1: Twelve seated subjects were exposed to continuous horizontal translational oscillation through the body x-axis (3.1 m · s⁻² peak acceleration, 0.20 Hz) while making head tilts which were either aligned or misaligned (180° out of phase) with respect to GIF. The two sessions were one week apart at the same time of day, counterbalanced for order. Head tilts were controlled by tracking a moving LED display and head trajectory was verified by accelerometry. Motion continued until moderate nausea was achieved (motion endpoint) or until a 30 min cut-off. Exp 2: A different group of 12 subjects were exposed to continuous horizontal translational sinusoidal oscillation through the body x-axis (2.0 m · s⁻² peak acceleration, 0.176 Hz) while seated in a cab which was tilted by suspension machinery around the y-axis of the ears so that GIF was aligned or misaligned (180° out of phase) with the body z-axis. Results: Exp 1: Mean ± SD time to motion endpoint was significantly longer for aligned (19.2 ± 12.0 min) than for misaligned (17.8 ± 13.0 min; p < 0.05, two-tail). Exp 2: Mean ± SD time to motion endpoint was significantly shorter for aligned (21.8 ± 10.9 min) than for misaligned (28.3 ± 5.8 min; p < 0.01, two-tail). Conclusions: Whether or not compensatory tilting protects against (Exp 1) or contributes to (Exp 2) motion sickness may be influenced by whether the tilting is under the active control of the person (e.g., car driver) or under external control (e.g., passenger in a high-speed tilting train).

Egi SM, Gürmen NM, Aydin S. Field trials of no-decompression stop limits for diving at 3500 m. Aviat Space Environ Med 2003; 74:228–35. Introduction: In 1990, Boğaziçi University (Istanbul, Turkey) launched an altitude diving program to develop techniques and safe decompression profiles for diving at high terrestrial altitudes. Following pioneering diving expeditions to lakes at high elevations in 1990–1992, it was deemed necessary to calculate new tables. Methods: Bottom time limits for dives requiring no decompression stops (no-d) were calculated for 3500 m using linear extrapolation of U.S. Navy M-values decreased by 4 ft of sea water (M4 limits). These limits were tested for 15, 18, 21, 24, 27, and 30 m of depth by diving in the Great Sea Lake at Mt Kaçkar (3412 m) with 10 dives per profile. Results: The mean decompression sickness (DCS) risk estimated from precordial bubble scores (Spencer Scale) ranged from 0.3% to 2.8% per profile. After three expeditions, 165 dives had been achieved with a cumulative bottom time of 3199 min. No DCS occurred in dives that adhered to the M4 no-d limits. However, two cases of Type I and one case of Type II DCS were encountered where the divers accidentally exceeded those limits. Discussion: Considering the estimated risk of DCS and the relatively small number of trials, a more conservative approach was used to develop a final set of high altitude dive tables. This conclusive approach used continuous compartment half-lives. It is based on fitting a surface of allowable supersaturation limits using the empirical M-values from existing tables as well as our altitude diving data, together with an added constraint that forces calculated M-values to stay below the available M-value data.

Englund M, Risberg J. Self-reported headache during saturation diving. Aviat Space Environ Med 2003; 74:236–41. Introduction: Some commercial divers have claimed that headache is a frequent symptom related to decompression following a saturation dive, but due to lack of systematic reporting there is limited knowledge of the incidence and clinical characteristics of such headaches. Methods: During 2001, a questionnaire was distributed to divers participating in offshore saturation diving operations on the Norwegian continental shelf. Two major diving contractors participated. The survey allowed anonymous self-reporting of past and present problems with headache; pain intensity was indicated daily on a visual analog scale (VAS) from 0 to 10. Of 95 divers, 56 participated and 67 saturations were registered. Results: The divers estimated a higher frequency of headaches in connection to saturation diving than in everyday life (p < 0.001). One third of the divers reported experiencing headache after they finished decompression. There was a significant increase in reports of headache on the last day of decompression (p = 0.03) and on the first day post-saturation (p < 0.001) compared with the start of decompression. Median headache duration was 6 h (range 1–84 h) and median pain score estimated on a VAS was 2.5 (range 0.1–7.8), equivalent to moderate intensity. Conclusions: Headache incidence is greater in divers during saturation diving than in everyday life. The increase is correlated to the last phase of decompression and the post-saturation period. No specific cause(s) of the headache could be identified, but we discuss possible explanations.

Kolka MA, Latzka WA, Montain SJ, Corr WP, O’Brien KK, Sawka MN. Effectiveness of revised fluid replacement guidelines for military training in hot weather. Aviat Space Environ Med 2003; 74:242–6. Background: This study compared the revised U.S. Army fluid replacement guidelines (REV) with the old guidelines (OLD) on daily changes in serum sodium concentration (Na⁺) and body mass (BM) during Basic Combat Training at Fort Benning, GA during two successive summers. Methods: Recruits (n = 550; OLD = 277, REV = 273) were evaluated before and after 8–12 h of outdoor military combat training in hot weather. The WBGT (mean ± SD) averaged 26.6 ± 1.7°C for OLD and 27.4 ± 0.9°C for REV (NS). Results: Serum Na⁺ decreased from 137.5 ± 1.6 mEq · L⁻¹ to 137.0 ± 2.1 mEq · L⁻¹ after outdoor military training in OLD (p < 0.05). Twenty-two recruits (8%) had serum sodium fall to below 135 mEq · L⁻¹ during OLD. Serum Na⁺ increased from 139.0 ± 1.7 mEq · L⁻¹ to 139.4 ± 2.1 mEq · L⁻¹ after outdoor military training in REV (p < 0.05). Only two recruits (1%) had serum Na⁺ fall to below 135 mEq · L⁻¹ during REV. BM increased an average of 1.3 ± 1.4 kg (p < 0.05) in OLD and an average of 0.4 ± 1.7 kg in REV (p < 0.05). Conclusions: The revised guidelines effectively reversed the decrease in serum sodium, reduced the increase in body mass, maintained hydration and minimized overdrinking during hot weather military training compared with the old fluid replacement guidelines.

Giannakoulas G, Katramados A, Melas N, Diamantopoulos I, Chimonas E. Acute effects of nicotine withdrawal syndrome in pilots during flight. Aviat Space Environ Med 2003; 74:247–51. Background: Pilots who smoke are occasionally obliged to abstain from nicotine intake during flight and may during this period exhibit certain symptoms leading to performance decrement. Methods: We studied 20 healthy male aviators, who were regular smokers, (mean age 33.7 ± 1.4 yr) operating military fixed- and rotary-wing aircraft (C-47 Dakota, F-16, A. Bell 205). All pilots were subjected to a 12-h abstinence from cigarette smoking, during which time they performed flight duties. After landing, we studied the intensity of the nicotine withdrawal syndrome, as well as its effect on physiological parameters, psychological functions, and cognitive tasks. This was achieved by the completion of a questionnaire, measurement of BP and heart rate, and the execution of certain computerized performance assessment tests. These tests measure mental arithmetic, visual vigilance, and image free-recall. In a subsequent flight performed under similar conditions, every pilot repeated the procedure without smoking deprivation. Thus, each subject served as his own control. The Wilcoxon non-parametric test was applied for statistical analysis. Results: The most frequent symptoms reported during nicotine deprivation were nervousness, craving for tobacco, tension-anxiety, fatigue, difficulty in concentration, decrease in alertness, disorders of fine adjustments, prolonged reaction times, anger-irritability, drowsiness, increase in appetite, and impairment of judgement. Systolic BP and heart rate tended to decrease and diastolic BP tended to rise during withdrawal, although the differences were not statistically significant. Finally, all tests recorded an impairment of cognitive functions during abstinence. Conclusion: Abrupt cessation of smoking may be detrimental to flight safety and the smoking withdrawal syndrome may influence flying parameters.

Chaturvedi AK, Smith DR, Soper JW, Canfield DV, Whinnery JE. Characteristics and toxicological processing of postmortem pilot specimens from fatal civil aviation accidents. Aviat Space Environ Med 2003; 74:252–9. Introduction: Autopsied biosamples from civil aviation accident pilot fatalities are submitted to the Civil Aerospace Medical Institute (CAMI) for toxicological evaluation. However, such evaluation is dependent on types and amounts of submitted samples, and obtaining suitable samples is governed by the nature of the accident. Characteristics of those samples and associated toxicological processing have not been well documented in the literature. Method: Therefore, the CAMI Toxicology Database was searched for these aspects. Results: CAMI received samples from the pilot fatalities (CAMI cases) of approximately 80% of the 1990–2000 aviation accidents reported by the National Transportation Safety Board. Accidents and cases during June-September were higher than the other months, and more than half of the received cases had multiple samples in sufficient amounts. For example, out of 1891 cases processed for the 1996–2000 accidents, 1211 had at least adequate amounts of blood, urine, and/or vitreous humor; 324 had inadequate amounts of blood and urine; and 356 had no blood or urine. Muscle, liver, lung, and/or kidney samples were submitted in 90% of the cases, while cerebrospinal fluids were submitted in only 8% of the cases. The toxicologically preferred samples, blood and urine, were available in 78% and 56% of the 1891 cases, respectively. Out of 51 cases containing only one sample type, 46 had muscle and the remaining 5 had other sample types. Samples were primarily analyzed for combustion gases, alcohol/volatiles, and drugs. Generally, the presence of analytes is demonstrated in at least two different sample types by using two different analytical techniques for reporting a particular case as “positive.” An effective quality-assurance/quality-control is maintained throughout the process. Conclusion: In the majority of the aviation accidents, sufficient amounts and types of biological samples were submitted for toxicological evaluation.

Thomas TL, Garland FC, Molé D, Cohen BA, Gudewicz TM, Spiro RT, Zahm SH. Health of U.S. Navy submarine crew during periods of isolation. Aviat Space Environ Med 2003; 74:260–5. Background: An essential element in planning for long-term space missions is prediction of the medical support required. Medical data for analogous populations serving in isolated and/or contained environments are useful in predicting health risks for astronauts. Methods: This study evaluated the rates of health events that occurred among a highly screened, healthy military population during periods of isolation using a centralized database of medical encounter records from U.S. Navy submarines. The study population was composed of U.S. Navy officers and enlisted men deployed on 240 submarine patrols between 1 January 1997 and 30 September 2000. Results: A total of 1389 officers and 11,952 enlisted crew members served aboard participating submarines for 215,086 and 1,955,521 person-days at sea, respectively, during the study period. Officers had 214 initial visits to medical staff with 79 re-visits for the same condition during these patrols, while enlisted men had 3345 initial visits and 1549 re-visits. Among officers, the most common category of medical events was respiratory illnesses (primarily upper respiratory infections), followed by injury, musculoskeletal conditions, infectious diseases, symptoms and ill-defined conditions, and skin problems. Among enlisted men, the most common category of medical events was injury, followed by respiratory illnesses (upper respiratory infections), skin problems, symptoms and ill-defined conditions, digestive disorders, infectious conditions, sensory organ problems (ear infections and eye problems), and musculoskeletal conditions. Conclusions: Potential mission-impacting medical events reported were rare, i.e., among a crew of seven officers, only one medical event would be expected to occur during a 6-mo mission and result in 3/4 d or less of limited or no duty. Among a crew of seven enlisted men, about two medical events would be expected during a 6-mo mission and result in about 1 d of limited or no duty per medical event.

Kraft NO, Lyons TJ, Binder H. Group dynamics and catecholamines during long-duration confinement in an isolated environment. Aviat Space Environ Med 2003; 74:266–72 Introduction: The objectives of this study were to investigate possible relationships between catecholamine excretion and long-duration confinement in an isolated environment. Methods: Stays of long duration were made by Group I (n = 4, all Russian, weeks 1–34), Group II (n = 4, mixed nationality, weeks 3–18), and Group III (n = 4, mixed nationality, weeks 22–38); other groups joined the residents for 1-wk intervals at weeks #13, #19, and #33. Data were collected from Groups I and III. Results: In both Group I and Group III, the daily epinephrine excretion was significantly elevated during and after confinement compared with the pre-isolation baseline (p < 0.05), but remained mostly within normal limits during the experiment. During isolation, epinephrine excretion was significantly higher, compared with other weeks in isolation, during weeks #19 and #27 for Group I, and during week #30 for Group III. In both Group I and Group III, norepinephrine excretion increased significantly during and after isolation (p < 0.05) and was above the normal range. The daily norepinephrine excretion was significantly higher (p < 0.05) in Group I during weeks #12, #13, and #27, and during week #30 for Group III. Discussion: Epinephrine excretion generally remained in the normal range. However, occasional elevations occurred due to psychological stress, which apparently correlate with changes in group dynamics. Norepinephrine excretion was above the normal range and was correlated with social events. These results suggest that to ensure optimum crew performance, entire crews along with their visiting crews should be selected collectively, rather than individually.

Kraaij V, Garnefski N, van Gerwen L. Cognitive coping and anxiety symptoms among people who seek help for fear of flying. Aviat Space Environ Med 2003; 74:273–7. Introduction: Fear of flying among potential passengers is rather common. In order to treat fear of flying most efficiently, it is important to find out which aspects are related to flight anxiety. The objective of the present study was to examine the extent to which various cognitive coping strategies in response to a flight were used by airline passengers and their relationship with anxiety symptoms. Method: A total of 261 persons who were all seeking treatment for fear of flying filled in the Cognitive Emotion Regulation Questionnaire, the anxiety subscales of the Symptom Check List (SCL-90), the Flight Anxiety Situations questionnaire, and the Flight Anxiety Modality questionnaire. Results: Respondents reported using refocus on planning, rumination, putting into perspective to the highest extent, and catastrophizing and other-blame to the lowest extent. Furthermore, respondents who reported using self-blame, acceptance, rumination, and/or catastrophizing to a higher extent, also reported significantly higher levels of anxiety. Discussion: As the present study suggests that several cognitive coping strategies are related to anxiety, intervention programs should pay attention to these aspects. The present study gives important clues about which cognitive coping strategies should be challenged in treatment of flight anxiety.

Goerres H-P, Weber F. Elevated bilirubin and visual perception in pilots. Aviat Space Environ Med 2003; 74:278–80. Background: A fatal aircraft accident of a Bo-105 helicopter on May 20, 1996 led to the suspicion that the pilot’s raised serum bilirubin level could have contributed to the accident. It was suspected that an increase of bilirubin beyond 20.52 μmol · L⁻¹ could disturb visual perception. Methods: In 1998 and 1999, 101 pilots with functional hyperbilirubinemia, diagnosed as Gilbert’s syndrome, were subjected to perceptual-psychological testing (signal detection test) during their periodic medical examinations at the German Air Force Institute of Aviation Medicine. The results of the psychophysiological testing were compared with a control group. Results: Reaction time and perception range increased with age and were independent of serum bilirubin level. Conclusion: There is no evidence that raised serum bilirubin levels can diminish visual perceptional performance.

Moran DS, Heled Y, Shani Y, Epstein Y. Hypothermia and local cold injuries in combat and non-combat situations-the Israeli experience. Aviat Space Environ Med 2003; 74:281–4. Introduction: Cold weather has been recognized in the Israel Defense Forces (IDF) as a potential medical and operational threat to the soldier. Although regulations have been issued to cope with this situation, every year about 20 cases of hypothermia (Tcore < 35°C) and peripheral cold injuries are reported. Methods: This study was aimed at following cold weather injuries (CI) in the IDF in the period 1994–2001. 136 cases were reported to our institute during this period. All patients were from the general population of young (20 ± 2 yr), male soldiers in the IDF. All were classified a priori as healthy, active subjects. Results: Of these patients, 51% were diagnosed with mild hypothermia and 49% with peripheral CI. Among those soldiers who suffered from peripheral CI, less than 5% were diagnosed with frostbite. Most of the cases (76%) occurred in the winter months; however, 10% occurred in the spring, 13% in autumn, and 2 cases (1%) were reported in the summer. The majority of all CI cases occurred during routine scheduled training (51%), and 15% occurred during routine duties. Of the cases, 34% occurred during combat operations (mainly ambushing and surveillance). Discussion: The present study provides data on CI cases in an army where the awareness of the hazards involved in hostile environments is extensive, and in which detailed regulations aimed to prevent these injuries are common practice. The Israeli experience indicates that CI is preventable in most instances by following a few simple regulations and providing proper education to the soldiers and their commanding officers.

Ahn SC. Short-term vestibular responses to repeated rotations in pilots. Aviat Space Environ Med 2003; 74:285–7. Introduction: It has been suggested that vestibular function in pilots differs from that of non-pilots. Methods: Short-term vestibular responses to repeated rotations were explored in pilots and non-pilots using a rotating chair. Vestibulo-ocular reflex tests were done in 30 pilots (VOR-P) and 30 non-pilots (VOR-NP) at rotation frequencies of 0.01, 0.02, 0.04, 0.08, 0.16, and 0.32 Hz. In a separate experiment, VOR tests were done at 0.16 Hz before and after four successive velocity-step tests in twenty-five pilots (STEP-P) and their results were compared with the results of twenty-five non-pilots (STEP-NP) who were studied earlier. Results: VOR-P exhibited normal VOR gains (mean values 0.47, 0.57, 0.63, 0.69, 0.67, and 0.74, respectively, for the frequencies listed above) compared with those of VOR-NP (0.48, 0.54, 0.59, 0.67, 0.72, and 0.79). VOR gain at 0.16 Hz showed little change in STEP-P (0.64 ± 0.04 to 0.58 ± 0.032), while it increased in STEP-NP (0.59 ± 0.03 to 0.78 ± 0.06). Discussion: VOR gain may be a useful measurement for differentiating pilots’ vestibular function from that of non-pilots. After-rotary VOR may be suppressed in pilots.

Alan M. Sleep apnea: a case report. Aviat Space Environ Med 2003; 74:288–90.