Aviation, space, and environmental medicine最新文献

Background: Between June-October 2012, 61 flight-medic-directed transfusions took place aboard U.S. Army Medical Evacuation (medevac) helicopters in Afghanistan. This represents the initial experience for pre-hospital blood product transfusion by U.S. Army flight medics.

Methods: We performed a retrospective review of clinical records, operating guidelines, after-action reviews, decision and information briefs, bimonthly medical conferences, and medevac-related medical records.

Results: A successful program was administered at 10 locations across Afghanistan. Adherence to protocol transfusion indications was 97%. There were 61 casualties who were transfused without any known instance of adverse reaction or local blood product wastage. Shock index (heart rate/systolic blood pressure) improved significantly en route, with a median shock index of 1.6 (IQR 1.2-2.0) pre-transfusion and 1.1 (IQR 1.0-1.5) post-transfusion (P < 0.0001). Blood resupply, training, and clinical procedures were standardized across each of the 10 areas of medevac operations.

Discussion: Potential risks of medical complications, reverse propaganda, adherence to protocol, and diversion and/or wastage of limited resources were important considerations in the development of the pilot program. Aviation-specific risk mitigation strategies were important to ensure mission success in terms of wastage prevention, standardized operations at multiple locations, and prevention of adverse clinical outcomes. Consideration of aviation risk mitigation strategies may help enable other helicopter emergency medical systems to develop remote pre-hospital transfusion capability. This pilot program provides preliminary evidence that blood product administration by medevac is safe.

Introduction: Flight deck alerts provide system malfunction information designed to lead corresponding pilot reactions aimed at guaranteeing flight safety. This study examined the roles of expertise and flight responsibility and their relationship to pilots' reactions to flight deck alerts.

Methods: There were 17 pilots composing 12 flight crews that were assigned into pairs according to flight hours and responsibilities. The experiment included 9 flight scenarios and was carried out in a CRJ-200 flight simulator. Pilot performance was recorded by a wide angle video camera, and four kinds of reactions to alerts were defined for analysis.

Results: Pilots tended to have immediate reactions to uninterrupted cautions, with a turning off rate as high as 75%. However, this rate decreased sharply when pilots encountered interrupted cautions and warnings; they also exhibited many wrong reactions to warnings. Pilots with more expertise had more reactions to uninterrupted cautions than those with less expertise, both as pilot flying and pilot monitoring. Meanwhile, the pilot monitoring, regardless of level of expertise, exhibited more reactions than the pilot flying. In addition, more experienced pilots were more likely to have wrong reactions to warnings while acting as the monitoring pilot.

Conclusions: These results suggest that both expertise and flight responsibility influence pilots' reactions to alerts. Considering crew pairing strategy, when a pilot flying is a less experienced pilot, a more experience pilot is suggested to be the monitoring pilot. The results of this study have implications for understanding pilots' behaviors to flight deck alerts, calling for specialized training and design of approach alarms on the flight deck.

Background: High altitude illnesses (HAI) are a risk factor for any individual who is exposed to a significant increase in altitude. To learn more about the epidemiology of HAI, we sought to determine if health records from a commercial trekking company could provide novel data on the prevalence of HAI, as well as efficacy data regarding common HAI therapeutics.

Methods: Health parameters from 917 tourists ascending Mt. Kilimanjaro over a 10-yr period were analyzed for meaningful data.

Results: Of all subjects, 70% experienced at least one instance of a symptom related to HAI (headache, nausea, vomiting, diarrhea, or loss of appetite) during the trek. Acetazolamide was used at least once by 90% of subjects and, of those who used acetazolamide, 92% began taking it on day 1 of the ascent. Acetazolamide was found to improve oxygen saturation 1.2% above 9842.5 ft (3000 m). Dexamethasone use 12 h prior to ascending above 18,996 ft (5790 m) decreased the probability of a subject exhibiting at least one AMS symptom at that altitude.

Discussion: The prevalence of AMS symptoms was not reduced by taking 2 extra days to reach the summit of Mt. Kilimanjaro. Prophylactic acetazolamide modestly improved oxygen saturation; however, it did not reduce symptoms. Therapeutic dexamethasone, especially at higher altitudes, was effective at reducing symptoms. We conclude that meaningful high altitude physiological data can be obtained from private trekking companies.

Background: A major part of testing of rebreather apparatuses for underwater diving focuses on the oxygen dosage system.

Methods: A metabolic simulator for testing breathing apparatuses was built and evaluated. Oxygen consumption was achieved through catalytic combustion of propene. With an admixture of carbon dioxide in the propene fuel, the system allowed the respiratory exchange ratio to be set freely within human variability and also made it possible to increase test pressures above the condensation pressure of propene. The system was tested by breathing ambient air in a pressure chamber with oxygen uptake (Vo₂) ranging from 1-4 L · min(-1), tidal volume (VT) from 1-3 L, breathing frequency (f) of 20 and 25 breaths/min, and chamber pressures from 100 to 670 kPa.

Results: The measured end-tidal oxygen concentration (Fo₂) was compared to calculated end-tidal Fo₂. The largest average difference in end-tidal Fo₂during atmospheric pressure conditions was 0.63%-points with a 0.28%-point average difference during the whole test. During hyperbaric conditions with pressures ranging from 100 to 670 kPa, the largest average difference in Fo₂was 1.68%-points seen during compression from 100 kPa to 400 kPa and the average difference in Fo₂during the whole test was 0.29%-points.

Conclusion: In combination with a breathing simulator simulating tidal breathing, the system can be used for dynamic continuous testing of breathing equipment with changes in VT, f, Vo2, and pressure.

Background: Nitrogen (N2) in air causes cognitive impairment from gas narcosis when breathed at increased ambient pressures. This impairment might be reduced by using enriched air nitrox (EANx) mixtures, which have a higher oxygen and lower N2 content compared to air. This study aimed to investigate if divers differed in memory ability and self-assessment when breathing air and EANx30.

Methods: The effect of depth (shallow vs. deep) and breathing gas (air vs. EANx30) on memory ability and subjective ratings of impairment was compared in 20 divers.

Results: Memory performance was significantly worse in deep water (Air: M = 22.1%, SD = 21.7%; EANx30: M = 22.1%, SD = 17.2%) compared to shallow water (Air: M = 29.2%, SD = 18.3%; EANx30: M = 33.3%, SD = 18.2%), but this impairment did not differ significantly between air and EANx30. Subjective ratings of impairment increased significantly from shallow water (Air: M = 5.2, SD = 5.9; EANx30: M = 3.0, SD = 4.4) to deep water (Air: M = 36.8, SD = 25.3; EANx30: M = 24.8, SD = 16.1) when breathing both air and EANx30. However, ratings were significantly lower when breathing EANx30 compared to air when in the deep water.

Discussion: It was concluded EANx30 does not reduce narcotic impairment over air. Additionally, divers were able to make a correct global self-assessment they were impaired by narcosis, but were unable to make a finer assessment, leading them to erroneously believe that EANx30 was less narcotic than air.

Background: Lower back pain is ubiquitous in the helicopter community and testicular cancer is the most common solid organ tumor that affects approximately 1% of men ages 15 to 35. However, rarely is lower back pain caused by testicular cancer and, in an otherwise healthy male, it is generally low on the differential diagnosis. Literature review discovered the most recent case report where lower back pain was the presenting symptom for testicular cancer was in 1987.

Case report: A 26-yr-old male helicopter pilot presented to clinic complaining of lower back pain for greater than 1 yr for which conservative treatment had failed. The pain was so severe he was unable to sleep and had to remove himself from the flight schedule. The patient was seen by physical therapy and a chiropractor and treated with NSAIDs and other pain medications, including narcotics. After further investigation, it was discovered that the patient's lower back pain was a result of a retroperitoneal metastatic tumor originating from his right testicle.

Discussion: It is important to consider that, although most aviators in their twenties have been screened for chronic illness, they are still at risk for developing cancer. In this case, the patient never complained of testicular mass or pain and even denied symptoms during review of systems questioning. Proper education regarding the importance of self-examination and reporting of abnormalities is key to early detection and intervention. The 5-yr survival for metastatic testicular cancer is greater than 95%.

Background: At +1 Gz, electrical muscle stimulation (EMS) has been shown to increase systemic blood pressure similarly to a standard G-suit or lower body muscle straining. It was hypothesized that EMS might improve G protection at increased G levels.

Methods: An EMS suit was developed with electrodes over the calves, thighs, gluteal, and abdominal muscles. Using nine subjects, the EMS suit was compared to a standard five-bladder G-suit during various G profiles up to +9 Gz in a human-rated centrifuge with EMS activated by electrical muscle stimulators at G levels at or above +4 Gz. The optimal EMS stimulation for a solid muscle contraction was determined for each muscle group in each subject prior to the G exposures.

Results: The mean maximal G level attained in the standard suit was 1.1 G higher during a relaxed gradual onset profile, 1.5 G higher during a relaxed rapid onset profile, and 2.0 G higher during a straining rapid onset profile when compared to the EMS suit. During a simulated aerial combat maneuver (SACM) ride, duration was 46 s longer with the standard suit compared to the EMS. During the SACM, the average heart rate was 23 bpm lower with the standard suit compared to EMS. All of the above differences were statistically significant. Finally, there were four G-LOCs with the EMS and none with the standard suit.

Conclusion: The tested EMS suit did not give sufficient G protection at high Gs for pilots, nor substitute for a standard G-suit, as indicated by lower G protection and the episodes of G-LOC.