Samel A, Vejvoda M, Maass H. Sleep deficit and stress hormones in helicopter pilots on 7-day duty for emergency medical services. Aviat Space Environ Med 2004; 75:935–940. Introduction: Helicopter-based emergency medical services in Germany operate from sunrise to sunset, requiring up to 15.5 h of continuous duty during the summer months for pilots, who work for seven consecutive days. Because of concerns regarding the safety of this procedure with respect to pilot fatigue and stress, the German Ministry of Transport asked our laboratory to investigate the risks involved. Methods: There were 13 pilots (mean age 38 yr) who were studied in the summer months for 2 d before, 7 d during, and 2 d after their duty cycle. Measured variables included sleep duration and quality, subjective fatigue, and heart rate, as well as 24-h excretion levels of stress hormones. Results: During actual helicopter operations, maximum heart rates did not exceed 120 bpm. Over the 7-d duty period, mean sleep duration decreased from 7.8 h to 6 h or less, resulting in a cumulative sleep loss of about 15 h. Mean levels of excreted adrenalin, noradrenalin, and cortisol increased significantly by 50 to 80%; cortisol and noradrenalin excretion also remained elevated for the two post-duty days. Conclusions: Although the actual flights did not cause critical physiological responses, the acute and accumulated sleep deficit led to incomplete recuperation between duty hours and induced elevated stress indicators. It was, therefore, recommended that the duty cycle be amended as follows: 1.) enforce a 10-h rest period and at least an 8-h sleep opportunity per day; 2.) modify the duty period to allow no more than 3 consecutive rest periods of reduced sleep opportunities (8.5 h); and 3.) follow duty with several days that offer unrestricted sleep opportunities.

Prisby RD, Nelson AG, Latsch E. Eccentric exercise prior to hindlimb unloading attenuated reloading muscle damage in rats. Aviat Space Environ Med 2004; 75:941–946. Introduction: Antigravity muscles that are reloaded subsequent to hindlimb unloading (HU) are prone to injury. Similarities exist between muscle damage elicited from HU and subsequent reloading and damage induced by eccentric exercise (EE). Conditioning bouts of EE reduce muscle damage following a repeat bout of EE. Since damage to reloaded skeletal muscle is comparable to damage observed after EE, the mechanisms of damage are presumably similar. Therefore, EE prior to HU may attenuate reloading muscle damage. This study evaluated the effects of prior EE on rat soleus muscles (SOL) subsequent to 7 d of HU and 16–19 h of reloading. Methods: Sprague Dawley rats were randomly assigned to the following groups: eccentric exercise + hindlimb unloading + reloading (EEHUR; n = 9); hindlimb unloading + reloading (HUR; n = 10); eccentric exercise (EE; n = 12), or control (CON; n = 12). The exercise protocol was performed 5 d · wk⁻¹ for 2 wks followed by HU and reloading. Results: Fiber areas were lower in both suspended groups vs. the EE and CON groups. There was no difference in percent interstitial area among groups. However, percent myofibrillar damage was higher in the HUR group vs. all other groups. Further, glucose-6-phospate dehydrogenase activity, an indicator of muscle damage, was higher in the HUR group compared with the EE and CON groups. Conclusion: These results provide some evidence that prior EE reduced muscle damage subsequent to HU and reloading. Therefore, EE may prove effective in minimizing recovery time in individuals suffering from muscle damage following periods of bed rest and spaceflight.

Hinghofer-Szalkay H, Haditsch B, Loder I, Pilz K, Rössler A, Jezova D. Head down tilt at −6° to −24° can neutralize the cardiovascular effects of LBNP at −15 or −35 mmHg. Aviat Space Environ Med 2004; 75:947–951. Introduction: The purpose of this study was to identify the combinations of head down tilt (HDT) and lower body negative pressure (LBNP) that would counterbalance each other’s effects on cardiovascular and endocrine variables to produce a “neutral point” (NP). Methods: We conducted 8 30-min experiments in 14 normotensive subjects (2 male, 12 female). Conditions included four levels of HDT (−6° to −24°) and two of LBNP (−15 and −35 mmHg). We determined blood plasma mass density, hematocrit, plasma aldosterone concentration, and plasma renin activity (PRA) before and at the end of stimulation. The effect of stimulus duration was tested using continuous measurements of heart rate (HR), blood pressure (BP), and thoracic electrical impedance (Z0). Results: NPs were found for all variables except BP, which remained unchanged. NPs were similar for all variables. The 15 mmHg LBNP was compensated by 20° HDT and 35 mmHg LBNP by 27.5° HDT. Longer stimulus duration required increasing HDT angles to balance HR at 35 mmHg LBNP but had no influence on Z0 NP. Discussion: Antiorthostatic positioning can compensate cardiovascular effects of LBNP in a similar fashion for all variables that are significantly influenced by LBNP and body angle, commensurate with stimulus magnitude. Arterial BP remained stable with stimulation and seems to be the primarily defended variable. Why stimulus duration seems to influence the NP for HR remains to be elucidated.

Sandor PMB, Pellieux L, Godfroy M, Ossard G, Dancer A. Hearing thresholds during Gz acceleration with masking noise. Aviat Space Environ Med 2004; 75:952–955. Background: Future fighter aircraft will include three-dimensional sound signals as part of the human-machine interface. The reduction in cerebral vascular flow associated with maneuvering acceleration (+Gz) may affect a pilot’s ability to perceive and interpret such aural cues. We hypothesized that vascular deprivation along the cochlea produced by +Gz would raise hearing thresholds either globally or specifically at 1000 Hz. Methods: We compared hearing thresholds for pure tones at 250, 1000, 6000 and 10,000 Hz during exposure to +1 Gz vs. +4 Gz. Experiments were conducted with steady noise input to the earphones to mask centrifuge noise. Results: Paradoxically the hearing threshold was slightly yet significantly reduced for 1000 Hz (53 dB at 1 G vs. 47 dB at 4 G) while remaining unchanged at other frequencies. Discussion: Audition did not change at +4 Gz, contradicting our hypothesis. We infer that the change at 1000 Hz is not a central effect, but instead represents a disturbance of middle ear transmission mechanisms. The absence of any general hearing loss at +4 Gz favors the possibility of using complex sounds such as three-dimensional sound in aeronautical human-machine interfaces during acceleration.

Scott CG, Ducharme MB, Haman F, Kenny GP. Warming by immersion or exercise affects initial cooling rate during subsequent cold water immersion. Aviat Space Environ Med 2004; 75:956–963. Introduction: We examined the effect of prior heating, by exercise and warm-water immersion, on core cooling rates in individuals rendered mildly hypothermic by immersion in cold water. Methods: There were seven male subjects who were randomly assigned to one of three groups: 1) seated rest for 15 min (control); 2) cycling ergometry for 15 min at 70% [V-dot]O₂peak (active warming); or 3) immersion in a circulated bath at 40°C to an esophageal temperature (Tes) similar to that at the end of exercise (passive warming). Subjects were then immersed in 7°C water to a Tes of 34.5°C. Results: Initial Tes cooling rates (initial ∼6 min cooling) differed significantly among the treatment conditions (0.074 ± 0.045, 0.129 ± 0.076, and 0.348 ± 0.117°C · min⁻¹ for control, active, and passive warming conditions, respectively); however, secondary cooling rates (rates following initial ∼6 min cooling to the end of immersion) were not different between treatments (average of 0.102 ± 0.085°C · min⁻¹). Overall Tes cooling rates during the full immersion period differed significantly and were 0.067 ± 0.047, 0.085 ± 0.045, and 0.209 ± 0.131°C · min⁻¹ for control, active, and passive warming, respectively. Discussion: These results suggest that prior warming by both active and, to a greater extent, passive warming, may predispose a person to greater heat loss and to experience a larger decline in core temperature when subsequently exposed to cold water. Thus, functional time and possibly survival time could be reduced when cold water immersion is preceded by whole-body passive warming, and to a lesser degree by active warming.

Caine-Bish NL, Potkanowicz ES, Otterstetter R, Glickman EL. Thermal and metabolic responses of sleep deprivation of humans during acute cold exposure. Aviat Space Environ Med 2004; 75:964–968. Purpose: This investigation evaluated the effects of 33 h of sleep deprivation on the thermoregulation in 12 male and female subjects (26.6 ± 6.4 yrs) during 180 min of cold exposure in 12°C air. Methods: Subjects underwent two cold air trials (CAT): one following a normal night of sleep (i.e., 6–8 h) (CON); and one following 33 h of sleep deprivation (SDEP). Rectal temperature (Tre), mean skin temperature ([Tmacr]sk), heat production (HP), and tissue insulation (I_{t i}), were measured at 5, 15, 30, and every 30 min thereafter. Results: ANOVA revealed no significant differences (p > 0.05) between CON and SDEP for Tre, [Tmacr]sk, HP, and I_{t i}. A main effect for time was demonstrated for Tre, I_{t i}, HP, and [Tmacr]sk. A trial × time interaction for Tre and [Tmacr]sk (p = 0.021) was demonstrated. Discussion: Significant interactions were demonstrated for Tre and [Tmacr]sk, but post hoc analysis determined no differences between SDEP and CON. This may have been due to the length of the sleep deprivation, cold stressor, or a combination of the two. There were also no overall differences in HP or I_{t i} between SDEP and CON. Further research in this area is needed to evaluate the effects of sleep deprivation during acute cold exposure.

Balldin UI, Pilmanis AA, Webb JT. Central nervous system decompression sickness and venous gas emboli in hypobaric conditions. Aviat Space Environ Med 2004; 75:969–972. Introduction: Altitude decompression sickness (DCS) that involves the central nervous system (CNS) is a rare but potentially serious condition. Identification of early symptoms and signs of this condition might improve treatment. Methods: We studied data from 26 protocols carried out in our laboratory over the period 1983–2003; all were designed to provoke DCS in a substantial proportion of subjects. The data set included 2843 cases. We classified subject-exposures that resulted in DCS as: 1) neurological DCS of peripheral and/or central origin (NEURO); 2) a subset of those that involved only the CNS (CNS); and 3) all other cases, i.e., DCS cases that did not have a neurological component (OTHER). For each case, echo imaging data were used to document whether venous gas emboli (VGE) were present, and their level was classified as: 1) any level, i.e., Grade 1 or higher (VGE-1); and 2) high level, Grade 4 (VGE-4). Results: There were 1108 cases of altitude DCS in the database; 218 were classified as NEURO and 49 of those as CNS. VGE-1 were recorded in 83.8% of OTHER compared with 58.7% of NEURO and 55.1% of CNS (both p < 0.001 compared with OTHER). The corresponding values for VGE-4 were 48.8%, 37.0%, and 34.7% (p < 0.001, compared to OTHER). Hyperbaric oxygen (HBO) was used to treat about half of the CNS cases, while all other cases were treated with 2 h breathing 100% oxygen at ground level. Discussion: Since only about half of the rare cases of hypobaric CNS DCS cases were accompanied by any level of VGE, echo imaging for bubbles may have limited application for use as a predictor of such cases.

Palinkas LA, Johnson JC, Boster JS, Rakusa-Suszczewski S, Klopov VP, Xue QF, Sachdeva U. Cross-cultural differences in psychosocial adaptation to isolated and confined environments. Aviat Space Environ Med 2004; 75:973–980. Introduction: Differences in patterns of psychosocial adaptation under conditions of prolonged isolation and confinement in Antarctica were examined to determine the extent to which they were influenced by national culture in general and the individualist-collectivist orientation of national cultures in particular. Methods: The Profile of Mood States and measures of structural and functional social support were administered over an 8-mo period (March through October) to 13 winter-over crews from 5 nations operating research stations in the Antarctic: United States (3 crews, n = 77), Poland (3 crews, n = 40), Russia (3 crews, n = 34), China (3 crews, n = 40), and India (1 crew, n = 26). Results: Americans at South Pole Station reported significant increases in fatigue and anxiety and a significant decrease in vigor over the winter. During the same period, Russians at Vostok Station reported significant decreases in depression, anxiety, and confusion, and Indians at Maitri Station reported a significant decrease in anger. A significant decrease in social interaction with fellow crewmembers occurred at South Pole Station, Vostok Station, and Poland’s Arctowski Station. Several differences were also observed between the five stations in correlations between mood scores and measures of structural and functional social support. An individualistic cultural orientation was significantly associated with low social support and low negative mood. Conclusion: Cultural background is associated with mood and social support as well as changes in these measures during the austral winter. Cultural differences in patterns of psychosocial adaptation must be considered in the formation and training of multinational crews for long duration missions in space.

Kumar R, Pasha Q, Khan AP, Gupta V. Renin angiotensin aldosterone system and ACE I/D gene polymorphism in high-altitude pulmonary edema. Aviat Space Environ Med 2004; 75:981–983. Introduction: People who visit high altitude are exposed to a stressful environment, and many of them suffer from altitude-induced conditions, including high altitude pulmonary edema (HAPE). We investigated the renin angiotensin aldosterone system (RAAS) and the possible association of angiotensin converting enzyme (ACE) insertion/deletion (I/D) gene polymorphism in the development of HAPE in Indian men. Methods: Subjects were all low-altitude natives: 19 men who developed HAPE within 1–3 d of arrival at 3000 to 3800 m (patients); and 20 age-matched men who did not develop HAPE during a period of a month or more at ≥ 3500 m (controls). We recorded the arterial oxygen saturation (S_aO₂), heart rate (HR), and blood pressure (BP) of both groups and measured their levels of plasma renin activity (PRA), ACE, aldosterone, and serum electrolytes. Polymerase chain reaction was used to investigate a 287 base pair alu repeat sequence I/D polymorphism in the ACE gene. Results: Compared with controls, patients showed a significantly lower S_aO₂ and a higher HR. They also had significantly higher plasma PRA, aldosterone, ACE, and serum sodium (Na⁺) and potassium (K⁺). No significant difference was observed in ACE I/D allele frequencies. Discussion: The results suggested that RAAS is involved in the development of HAPE in low-altitude natives, but there is no association of ACE I/D gene polymorphism with HAPE.

Conway GA, Hill A, Martin S, Mode NA, Berman MD, Bensyl DM, Manwaring JC, Moran KA. Alaska air carrier operator and pilot safety practices and attitudes: a statewide survey. Aviat Space Environ Med 2004; 75:984–991. Introduction: Aviation crashes are a leading cause of occupational fatalities in Alaska, with Alaskan pilots having nearly 100 times the fatality rate of U.S. workers overall. A survey was designed to study pilot and company practices and attitudes in order to develop intervention strategies that would reduce aviation fatalities. Methods: Two surveys were administered: one of air carrier operators and one of active commercial pilots. Surveys from 153 air taxi and public-use operators were received at a 79% response rate. Results: There are almost 2000 pilots employed in Alaska during peak season by air taxi operators and public agencies. Surveyed operators and pilots generally agreed that improved weather information and regional hazards training would be effective ways to prevent crashes. Operators were more in favor of operator financial incentives (p < 0.05) and better pre-employment hiring checks on pilots (p < 0.05) compared with pilots’ survey responses. There were 48% of pilots of large operators and 73% of pilots of small operators who considered their jobs to be at least as safe as other jobs. Conclusions: The results of operator-pilot comparisons suggest that financial pressures on operators may influence their views on what measures would be effective in preventing crashes, and that Alaskan pilots underestimate their occupational fatality risk.

Yıldız Ş, Aktaş Ş, Cimşit M, Ay H, To[g-breve]rol E. Seizure incidence in 80,000 patient treatments with hyperbaric oxygen. Aviat Space Environ Med 2004; 75:992–994. Introduction: Hyperbaric oxygen treatment (HBOT) involves some risk of central nervous system (CNS) oxygen toxicity, which may be revealed by various signs and symptoms including seizures in patients breathing O₂ at pressures of 2 ATA or higher. The aim of this study was to determine the incidence of such seizures in the Underwater and Hyperbaric Medicine Departments of two university hospitals. Methods: We retrospectively evaluated 80,679 patient-treatments for 9 clinical indications to determine the incidence of seizures attributable to CNS O₂ toxicity. Because different protocols were used for HBOT, the treatments were studied in four groups according to the chamber type used and the medical facility at which it was located. Results: Only 2 seizures were documented, yielding an incidence of 2.4 per 100,000 patient-treatments. Both cases occurred in a multiplace chamber pressurized to 2.4 ATA with O₂ delivered by mask for three × 30 min with 5-min air breaks. Discussion: The seizure incidence reported here is lower than other studies published in the literature. The delivery of O₂ by mask rather than hood may be a factor. Nevertheless, it appears that the risk of seizures due to CNS O₂ toxicity during HBOT is very low as long as appropriate exclusion criteria and treatment profiles are used.

Fife CE. Risk vs. benefit in hyperbaric medicine: a brief comment. Aviat Space Environ Med 2004; 75:995–996.

Grossman A, Barenboim E, Azaria B, Sherer Y, Goldstein L. Oral drug therapy for erectile dysfunction: overview and aeromedical implications. Aviat Space Environ Med 2004; 75:9971000.Approximately 150 million men worldwide experience erectile dysfunction, whereby they are unable to maintain an erection adequate for satisfactory sexual performance. This population is projected to more than double in the next 25 yr. Introduction of the phosphodiesterase inhibitors has revolutionized the management of this common problem, encouraging many more men to seek treatment. The issue of erectile dysfunction treatment is a growing concern in the aviation community as well. This is particularly relevant in civil aviation, as this population is older and has co-morbidities that may contribute to the development of erectile dysfunction. In this article we will review the available options for oral treatment of erectile dysfunction and discuss implications regarding their use in aviators based on the information available in the literature.

Critchley EP. Multiple sclerosis initially presenting as facial palsy. Aviat Space Environ Med 2004; 75:1001–1004.A case of multiple sclerosis initially presenting as a facial palsy is presented. A 35-yr-old U.S. Air Force aviator developed a purely right-sided facial palsy with no sensory abnormalities. She had no other neurologic findings except for a barely perceptible loss of coordination in her right upper extremity. Subsequent brain MRI revealed multiple white matter lesions. Further history and laboratory analysis confirmed multiple sclerosis. This case underscores the potential for multiple sclerosis to mimic other more benign conditions and the need for clinicians to carefully examine patients presenting with new neurologic abnormalities. The diagnosis and treatment of multiple sclerosis as well as military aviation policy regarding multiple sclerosis patients is discussed.

Tvaryanas AP. Cases from the aerospace medicine residents’ teaching file: furunculosis. Aviat Space Environ Med 2004; 75:1005–1008.A case is presented of an aviator with frequent dermatologic lesions concerning for recurrent furunculosis that was caused by community-acquired methicillin-resistant staphylococcus aureus. The presentation, diagnosis, treatment, and aeromedical disposition of recurrent furunculosis are discussed.