Aviation, space, and environmental medicine最新文献

Background: Airplane emergency medical services (AEMS) operators use fixed-wing airplanes to undertake rapid response, round-the-clock medical transport missions. This paper explores the structure of long-range, multileg AEMS missions and the sleep and sleepiness of the pilots who work them.

Methods: During nine long-range AEMS missions, pilots kept a sleep and sleepiness logbook and wore a wrist activity monitor to evaluate the timing of sleep/wake.

Results: Missions had a mean duration of 20 h 00 min ± 2 h 39 min, involved two to four flight legs, and were crewed by three or four pilots who rotated between operating and sleeping in curtained-off bunks. The pilots obtained a mean of 15 h 26 min ± 4 h 51 min and 7 h 54 min ± 1 h 33 min of sleep in the 48 h and 24 h prior to checking in for duty, respectively. During missions, a mean of 3 h 33 min ± 1 h 46 min of sleep was taken, usually across two in-flight sleep periods. Karolinska Sleepiness Scores (KSS) at top of climb and top of descent were typically less than 5 ('neither alert nor sleepy'). A small number of individual higher KSS scores were recorded on the longest missions and on flights between 02:00 and 06:00.

Discussion: These findings suggest that despite the long duration, timing, and multileg nature of AEMS missions, it is possible via careful design and management to operate these missions with appropriate levels of pilot alertness.

Introduction: The objective of this study was to observe the differences in the biodynamic responses of male and female crewmembers during a simulated Soyuz spacecraft (short-duration flights) impact landing.

Methods: There were 16 volunteers (8 men and 8 women) recruited to sit in a pseudo-supine position and be exposed to several impact acceleration pulses. The acceleration peaks ranged from 7.7 to 11.8 g with a duration of around 50 ms. Acceleration responses from the drop platform and seat, and at the volunteers' head, shoulder, chest, and ilium were measured.

Results: Results indicated that there were significant gender-based differences in the peak acceleration measured from volunteers' shoulders and iliums. The peak decelerations measured at the head and ilium were relatively higher than those measured at other levels on the seat.

Discussion: It was recommended that more attention be focused on the sex differences of biodynamic responses of crews in the study of new protective designs for space capsule and personal life support equipment.

Advances in microsensors, microprocessors, and microdisplays are creating new opportunities for improving vision in degraded environments through the use of head-mounted displays. Initially, the cutting-edge technology used in these new displays will be expensive. Inevitably, the cost of providing the additional sensor and processing required to support binocularity brings the value of binocularity into question. Several assessments comparing binocular, binocular, and monocular head-mounted displays for aided vision have concluded that the additional performance, if any, provided by binocular head-mounted displays does not justify the cost. The selection of a biocular [corrected] display for use in the F-35 is a current example of this recurring decision process. It is possible that the human binocularity advantage does not carry over to the aided vision application, but more likely the experimental approaches used in the past have been too coarse to measure its subtle but important benefits. Evaluating the value of binocularity in aided vision applications requires an understanding of the characteristics of both human vision and head-mounted displays. With this understanding, the value of binocularity in aided vision can be estimated and experimental evidence can be collected to confirm or reject the presumed binocular advantage, enabling improved decisions in aided vision system design. This paper describes four computational approaches-geometry of stereopsis, modulation transfer function area for stereopsis, probability summation, and binocular summation-that may be useful in quantifying the advantage of binocularity in aided vision.

Introduction: Accidental immersion in cold water is an occupational risk. Work suits and life jackets (LJ) should work effectively in combination to keep the airway clear of the water (freeboard) and enable self-righting. We hypothesized that inherent buoyancy, in the suit or LJ, would be beneficial for enabling freeboard, but its distribution may influence LJ self-righting.

Methods: Six participants consented to complete nine immersions. Suits and LJ tested were: flotation suit (FLOAT; 85 N inherent buoyancy); oilskins 1 (OS-1) and 2 (OS-2), both with no inherent buoyancy; LJs (inherent buoyancy/buoyancy after inflation/total buoyancy), LJ-1 50/150/200 N, LJ-2 0/290/290 N, LJ-3 80/190/270 N. Once dressed, the subject entered an immersion pool where uninflated freeboard, self-righting performance, and inflated freeboard were measured. Data were compared using Friedman's test to the 0.05 alpha level.

Results: All suits and LJs enabled uninflated and inflated freeboard, but differences were seen between the suits and LJs. Self-righting was achieved on 43 of 54 occasions, irrespective of suit or LJ. On all occasions that self-righting was not achieved, this occurred in an LJ that included inherent buoyancy (11/54 occasions). Of these 11 failures, 8 occurred (73% of occasions) when the FLOAT suit was being worn.

Discussion: LJs that included inherent buoyancy, that are certified as effective on their own, worked less effectively from the perspective of self-righting in combination with a work suit that also included inherent buoyancy. Equipment that is approved for use in the workplace should be tested in combination to ensure adequate performance in an emergency scenario.

Background: We examined the effects of plasma volume (PV) changes and flight duration on circulating soluble adhesion markers (sP-selection, sE-selection, and sICAM-1).

Methods: Study participants were 22 astronauts (2 women). Missions ranged from 5 to 16 d. Astronauts were split into two groups: those who spent less than 8 d in space and those who spent more than 8 d in space. Soluble adhesion markers and PV were assessed 10 d prelaunch, immediately after landing, and 2-4 d postflight.

Results: Compared to prelaunch, PV significantly decreased by 4.9% after landing and increased by 9.9% 2-4 d postflight. After landing, sICAM-1 decreased (233.15 vs. 226.78 ng · ml⁻¹) and remained lowered 2-4 d after landing (223.25 ng · ml⁻¹). Adjusting for PV changes, sICAM-1 upon landing was less than prelaunch (218.23 ng · ml⁻¹), but became greater 2-4 d postflight (250.30 ng · ml⁻¹). From prelaunch to landing, sE-selection decreased significantly (30.25 vs. 28.51 ng · ml⁻¹) and returned to prelaunch levels 2-4 d postflight (30.10 ng · ml⁻¹). Adjusting for PV changes, sE-selection was significantly greater 2-4 d postflight (33.48 ng · ml⁻¹) compared to prelaunch. In those who spent less than 8 d in space only, sP-selection increased from prelaunch levels to landing day (31.66 vs. 48.06 ng · ml⁻¹), with and without adjustment for PV changes. Flight duration did not influence PV, sICAM-1, or sE-selection.

Discussion: Spaceflight leads to an internal environment that decreases PV during flight but rebounds after flight, leading to a dilution of sICAM-1 and sE-selection, but does not appear to affect sP-selection. Flight duration only affected sP-selection.

NASA has recently updated spacecraft design requirements for protecting crewmembers during dynamic spaceflight phases. The details of the update are available in a NASA publication (NASA TM-2013-217380) and are summarized here. Previously, NASA's occupant protection requirements relied primarily on the multiaxial dynamic response criterion, which NASA refers to as the Brinkley Dynamic Response Criteria (BDRC). Although simple to implement, there are several important ground rules that must be met for the injury predictions to be applicable. These include proper restraint, flail controls, proper seating support, pressure suit considerations, head protection including consideration of helmet mass, and spaceflight deconditioning. Even if these ground rules are met, there are limitations to the model that must be addressed, including: model validation, sex differences, age effects, anthropometry effects, and differences between the physical fitness of military test subjects and future crewmembers. To address these limitations, new injury assessment reference values (IARV) have been prescribed for the 5(th) percentile female and 95(th) percentile male Hybrid III anthropomorphic test devices (ATD). These metrics are head-injury criterion, head-rotational acceleration, neck injury criterion, neck-axial-force limits, flail prevention, and lumbar-axial compression force. Using these new ATD IARVs, NASA can have increased confidence that vehicle designs mitigate the risk of injury during dynamic phases of flight.

Introduction: Syncope may be the initial clinical presentation of atrial fibrillation (AF) and has a great potential for incapacitation during flight. Herein is presented the case of a jet pilot who had paroxysmal palpitations accompanied with presyncope which progressed to syncope and was found to be associated with AF.

Case report: A 23-yr-old male jet pilot had a sudden syncope at the fifth minute of his presentation during the daily flight briefing. After he regained consciousness, he was transferred to the intensive care unit of the military hospital. His medical history revealed two episodes of syncope which resulted in spontaneous recovery and were not reported to the flight surgeon. He had no abnormal findings on his physical examination except heart rate, which was irregular and 110 bpm with a rapid ventricular response. His diagnosis was AF. Laboratory tests, including thyroid hormones, CBC, transthoracic echocardiography, ultrasonography of the abdomen, chest X-rays, and also a tilt table test, were normal. He had completely normal findings on 24-h ECG Holter monitoring except rare ventricular extrasystoles and had a negative treadmill stress test. AF spontaneously converted to sinus rhythm during the follow-up in the intensive care unit. He was temporarily grounded and returned to flying duties after a 3-mo follow-up period without any recurrent arrhythmia.

Discussion: Syncope has various mechanisms and etiologies, and also a benign prognosis on the ground. However, not only vasovagal syncope, but also AF may be among the frequent causes of syncope in aviators and pilots, as was the case in the current study.

Background: During early spaceflights, many crewmembers did not meet their caloric requirements and consequently lost body mass during flight, as assessed by a decrease in postflight body mass. Maintaining body mass during spaceflight is crucial for maintaining crew health and monitoring body mass is thus important to medical operations as well as being a key component of human research. Determining body mass becomes difficult in a microgravity environment.

Methods: We report data from two mass measurement devices on the International Space Station (ISS): the Russian body mass measuring device (BMMD), which uses spring oscillation physics, and NASA's Space Linear Acceleration Mass Measurement Device (SLAMMD), which uses Newton's second law of motion (F = ma).

Results: For 25 crewmembers whose body mass was measured on both devices, significant body mass loss occurred compared to preflight (gravimetric scale) and averaged -4.4% as assessed by BMMD and -2.8% as assessed by SLAMMD. After an initial loss in the first 30 d of flight, body mass remained constant through the rest of the mission, as determined using either device. The mean difference between the two devices was 1.1 kg when the closest SLAMMD and BMMD measurements were compared (6.9 ± 6.2 d apart). Dietary intake during flight is approximately 80% of the World Health Organization estimated requirement and the decrease in body mass follows in-flight energy intake closely on average.

Conclusion: Body mass monitoring is important for monitoring crew health during a mission and to help ensure that crewmembers consume adequate energy intake to mitigate the risks of spaceflight.

Introduction: Women increasingly occupy manual labor jobs. However, research examining women working under hot-humid conditions is lacking. Therefore, the purpose of our study was to assess how increasing relative humidity (RH) affects women's thermoregulation during low-intensity exercise characteristic of 8 h self-paced manual labor.

Methods: There were 10 women (age: 23 ± 2 yr; body-surface area: 1.68 ± 0.13 m²; Vo2max: 46 ± 6 ml · kg⁻¹ · min⁻¹) who walked 90 min at 35% Vo2max in 35°C at 55% RH (55RH), 70% RH (70RH), and 85% RH (85RH). Investigators obtained: 1) rectal temperature (Tre), mean-weighted skin temperature (Tsk), and heart rate every 5 min; and 2) respiratory measures every 30 min.

Results: Heat production (H) and required rate of evaporative cooling (Ereq) remained constant among trials; each RH increment significantly decreased evaporative heat loss (E), but increased heart rate and sweat rate. All other calorimetric and thermometric variables were similar between 55RH and 70RH, but significantly greater in 85RH. Tre only exceeded 38°C in 85RH after walking ∼80 min. Combined, dry and respiratory heat losses only compensated for <30% of the decreases in E.

Conclusion: Women exercising at low intensities in 35°C experienced most statistically significant physiological changes after 70RH. As H and Ereq remained constant across trials, heat storage increased with each 15% rise in RH because dry and respiratory heat losses minimally offset decreased E. Higher Tre, Tsk, and resultantly higher sweat rates reflected heat storage increases as E decreased in each trial. Overall, at 35°C Ta, we found women exercising for 90 min at low intensities remained at safe rectal temperatures up to 70% RH.