| 1. |
- Blogg, S. Lesley, et al.
(författare)
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Cerebral blood flow velocity and psychomotor performance during acute hypoxia
- 2006
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 77:2, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: The physiological effects of hypoxic environments can help determine safe limits for workers where cognitive and motor performance is important. We investigated the effects of a PIO2 of 15 kPa and 10 kPa on medial cerebral artery blood flow velocity (CBFV) and psychomotor performance. METHODS: Over 3 sessions, each involving 3 separate test batteries, 13 subjects breathed either 21 kPa PIO2 (control), 15 kPa PIO2, or 10 kPa PIO2. The tests measured reaction time, spatial orientation, voluntary repetitive movement, and fine manipulation. CBFV, PETCO2, PETO2, Sa02, and BP were recorded throughout. RESULTS: ANOVA analysis showed that 15 kPa PIO2 did not significantly change psychomotor test performance. The mean number of incorrect responses in the reaction time test significantly increased to 5.6 (SD - 4.0) while breathing 10 kPa PIO2, as did the mean number of errors (7.7 +/- 5.0) in the fine manipulation test. Only 10 kPa PIO2 affected CBFV, causing a significant increase in flow from 50 +/- 6.5 cm x s(-1) to 55 +/- 10.3 cm x s(-1). CBFV significantly increased during three psychomotor tests while breathing air; however, it did not increase further during psychomotor testing in hypoxia. DISCUSSION: A PIo2 of 15 kPa did not affect subject performance, and should not cause operational risk. At 10 kPa PIO2, accuracy and vigilance were slightly affected; however, the reduction in oxygenation was not great enough to cause major decrements. CBFV was not a good indicator of mental stress during hypoxia.
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| 2. |
- Brändström, Helge, et al.
(författare)
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Hand cold recovery responses before and after 15 months of military training in a cold climate
- 2008
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 79:9, s. 904-908
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: The ability of fingers to rapidly rewarm following cold exposure is a possible indicator of cold injury protection. We categorized the post-cooling hand-rewarming responses of men before and after participation in 15 mo of military training in a cold environment in northern Sweden to determine: 1) if the initial rewarming category was related to the occurrence of local cold injury during training; and 2) if cold training affected subsequent hand-rewarming responses. METHODS: Immersion of the dominant hand in 10 degrees C water for 10 min was performed pre-training on 77 men. Of those, 45 were available for successful post-training retests. Infrared thermography monitored the dorsal hand during 30 min of recovery. Rewarming was categorized as normal, moderate, or slow based on mean fingertip temperature at the end of 30 min of recovery (TFinger,30) and the percentage of time that fingertips were vasodilated (%VD). RESULTS: Cold injury occurrence during training was disproportionately higher in the slow rewarmers (four of the five injuries). Post-training, baseline fingertip temperatures and cold recovery variables increased significantly in moderate and slow rewarmers: TFinger30 increased from 21.9 +/- 4 to 30.4 +/- 6 degrees C (Moderate), and from 17.4 +/- 0 to 22.3 +/- 7 degrees C (Slow); %VD increased from 27.5 +/- 16 to 65.9 +/- 34% (Moderate), and from 0.7 +/- 2 to 31.7 +/- 44% (Slow). CONCLUSIONS: Results of the cold recovery test were related to the occurrence of local cold injury during long-term cold-weather training. Cold training itself improved baseline and cold recovery in moderate and slow rewarmers.
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| 3. |
- Eiken, Ola, et al.
(författare)
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G protection : interaction of straining maneuvers and positive pressure breathing
- 2007
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 78:4, s. 392-398
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: G protection in the 39 Gripen aircraft is provided by a full coverage anti-G suit, a pressure-breathing system, and anti-G straining maneuvers (AGSM). The purpose was to study (1) the interaction of pressure breathing and AGSM while wearing an anti-G suit; and (2) the G-protective properties of the anti-G suit alone and in combination with the pressure-breathing system. METHODS: During rapid onset rate G-time profiles (< or =9 G), 10 subjects were investigated in 5 conditions: (I) sitting relaxed, without any G-protective garment; (II) sitting relaxed and wearing an anti-G suit; (III) sitting relaxed, wearing an anti-G suit, and pressure breathing; IV) wearing an anti-G suit and performing AGSM; and V) wearing an anti-G suit, pressure breathing, and performing AGSM. In supplementary experiments (n=9), the share of the anti-G suit protection afforded by the abdominal bladder was investigated. RESULTS: G tolerance was 3.4 Gz (range: 2.8-4.3) in condition I, > or = 6.5 Gz (4.5-9.0) in II, > or = 8.0 Gz (6.5-9.0) in III, > or = 8.9 Gz (8.5-9.0) in IV and > or = 9.0 Gz (8.5-9.0) in V. In the supplementary experiments, the anti-G suit afforded a 2.8-G protection, a third of which was contributed by the abdominal bladder. In the relaxed state, pressure applied to the airways was transmitted undistorted to the intrathoracic space. During AGSM, intrathoracic pressure rose to 10-14 kPa, regardless of whether AGSM was performed with or without pressure breathing. DISCUSSION AND CONCLUSIONS: The anti-G suit and the pressure breathing system provide G protection of > or = 4.6 G, of which the anti-G suit contributes about 3.0 G. The C-protective properties of the anti-G suit and those of pressure breathing appears to be additive, whereas the G protection afforded by pressure breathing does not add to that provided by AGSM.
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| 4. |
- Eiken, Ola, et al.
(författare)
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Motion sickness decreases arterial pressure and therefore acceleration tolerance
- 2005
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 76:6, s. 541-546
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Motion sickness is a common aeromedical problem that may occur in pilots exposed to increased gravitoinertial load in the head-to-foot direction (+Gz). Since motion sickness may affect autonomic nervous functions including cardiovascular control, it was hypothesized that it might interfere with cardiovascular responses to high +Gz, thereby decreasing G tolerance. METHODS: G tolerance and cardiovascular responses to increased G load were studied in nine subjects in a centrifuge environment under two conditions. In the motion sickness condition, the subject was exposed to a motion sickness provocation (MSP) comprising repeated rapid changes in G load in combination with a regimen of head movements. In the control condition the subject was exposed to similar cumulative G-time stress, but without the MSP. Mean arterial pressure (MAP) was measured. An index of peripheral vascular resistance was achieved by measuring the difference in skin temperature between the forearm and fingertip (deltaT(forearm-fingertip)). RESULTS: MSP decreased gradual-onset rate G tolerance from 5.1 +/- 1.0 G (mean +/- SD) to 4.6 +/- 0.9 G. There was no change in gradual-onset rate G tolerance in the control condition. Rapid-onset rate G tolerance was lower in the motion sickness (2.9 +/- 0.5 G) than in the control (3.4 +/- 0.3 G) condition. MSP reduced MAP by 11 mmHg and deltaT(forearm-fingertip) by 4.2 +/- 4.1 degrees C. In the control condition MAP and deltaT(forearm-fingertip) were unaffected. CONCLUSIONS: Motion sickness may reduce the arterial pressure response to the extent that the capacity of an individual to withstand increased G loads in the head-to-foot direction is significantly diminished.
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| 5. |
- Eriksson, Lars, 1963-, et al.
(författare)
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Visual flow scene effects on the somatogravic illusion in non-pilots
- 2008
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 79:9, s. 860-866
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The somatogravic illusion (SGI) is easily broken when the pilot looks out the aircraft window during daylight flight, but it has proven difficult to break or even reduce the SGI in non-pilots in simulators using synthetic visual scenes. Could visual-flow scenes that accommodate compensatory head movement reduce the SGI in naive subjects? Methods: We investigated the effects of visual cues on the SGI induced by a human centrifuge. The subject was equipped with a head-tracked, head-mounted display (HMD) and was seated in a fixed gondola facing the center of rotation. The angular velocity of the centrifuge increased from near zero until a 0.57-G centripetal acceleration was attained, resulting in a tilt of the gravitoinertial force vector, corresponding to a pitch-up of 30 degrees. The subject indicated perceived horizontal continuously by means of a manual adjustable-plate system. We performed two experiments with within-subjects designs. In Experiment 1, the subjects (N = 13) viewed a darkened TIMID and a presentation of simple visual flow beneath a horizon. In Experiment 2, the subjects (N = 12) viewed a darkened HMD, a scene including symbology superimposed on simple visual flow and horizon, and this scene without visual flow (static). Results: In Experiment 1, visual flow reduced the SGI from 12.4 +/- 1.4 degrees (mean +/- SE) to 8.7 +/- 1.5 degrees. In Experiment 2, the SGI was smaller in the visual flow condition (9.3 +/- 1.8 degrees) than with the static scene (13.3 +/- 1.7 degrees) and without HMD presentation (14.5 +/- 2.3 degrees), respectively. Conclusion: It is possible to reduce the SGI in non-pilots by means of a synthetic horizon and simple visual flow conveyed by a head-tracked HMD. This may reflect the power of a more intuitive display for reducing the SGI.
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| 6. |
- Gennser, Mikael, et al.
(författare)
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Venous Gas Emboli in Goats After Simulated Submarine Escape from 290 msw Breathing Air or Hyperoxic Gas
- 2009
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 80:11, s. 927-932
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Tidskriftsartikel (refereegranskat)abstract
- GENNSER M, BLOGG. SL. Venous gas emboli in goats after simulated submarine escape from 290 msw breathing air or hyperoxic gas. Aviat Space Environ Med 2009; 80:927-32. Introduction: Escape from a disabled submarine has many inherent risks. Including the development of venous gas emboli (VGE) Breathing hyperoxic gas during rapid ascent from 2500 kPa (240 msw) reduces VGE, we Investigated whether it would also be beneficial during all escape from 3000 kPa (290 msw), thought to be at the limit of escape from a sunk sub Methods: Adult castrated male or female goats (45-85 kg, N = 35) Underwent dry chamber compression to 3000 kPa in 28 s, then decompressed at a rate of 2 75 m . s(-1) while breathing either air or hyperoxic gas (60/40%. O-2/N-2) Postsurfacing, precordial Doppler measurements were made using the Kisman Masurel (KM) scoring system, the animals were observed for signs of decompression illness (DCI) and/or oxygen toxicity Results: Six animals in the air group (N = 19) and two in the hyperoxic group (N = 10) suffered from severe I)pulmonary barotrauma on surfacing and were euthanized No cases of DO arose later than 5 min postsurfacing. Oxygen toxicity was not observed Although initial bobble Scores (median KM score 4) were the same in both groups, the time taken for the median KM score to reach 3 or less was significantly faster in the hyperoxic group (20 min vs 120 min) Disappearance of VGE was faster in the hyperoxic group Conclusion: Breathing hyperoxic gas during escape from 3000 kPa reduces the overall time. With circulating VGE and, despite exposure to a maximum inspired partial pressure, of oxygen of 1 8 MPa, symptoms of oxygen toxicity were not observed
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| 7. |
- Grönkvist, Mikael, et al.
(författare)
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G tolerance and pulmonary effects of removing chest counterpressure during pressure breathing
- 2005
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 76:9, s. 833-40
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In agile fighter aircraft positive pressure breathing is commonly used as part of the anti-G ensemble. To optimize G protection and prevent over-distention of the lungs, increased airway pressure is balanced by applying a counterpressure to the chest. The aim was to investigate the efficacy of chest counterpressure. METHODS: Three series of experiments were performed using the anti-G ensemble of the 39 Gripen aircraft (AGE-39) and exposing the subjects to 20-s G time profiles; in the first (n = 12) up to +8.0 Gz, in the second (n = 9) up to + 9.0 Gz, and also to simulated aerial combat maneuvers (SACM). Central and peripheral vision, arterial and airway pressures, pressure in the lower portion of the esophagus, and chest wall distension were measured. In the third series, six subjects were exposed to up to +7.0 Gz and esophageal pressure was measured in the upper thorax. In all series, two conditions were compared: with and without pressurized chest bladder. RESULTS: During the 20-s profiles arterial and esophageal pressures, chest wall distension, and visual impairment were similar with and without pressurized chest bladder. Upper esophageal pressure was slightly higher by 10-24% with than without chest bladder (p = 0.03). During SACM, time to exhaustion and the level of perceived exertion were similar with and without pressurized chest bladder. SUMMARY: The results suggest that the chest counterpressure can be removed from the AGE-39 without diminishing G tolerance or G endurance or significantly increasing the risk of lung parenchyma disruption.
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| 8. |
- Grönkvist, Mikael, et al.
(författare)
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Lung mechanics and transpulmonary pressures during unassisted pressure breathing at high Gz loads
- 2008
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 79:11, s. 1041-1046
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Positive pressure breathing (PPB) is commonly used in modern fighter aircraft as part of the anti-G ensemble. PPB is combined with a chest counterpressure bladder which is pressurized to the same magnitude as the breathing mask (balanced PPB). The chest counterpressure is expected to reduce the expiratory work of breathing, reduce the risk for lung rupture, and increase G tolerance. In a previous study we did not find any effect from chest counterpressure on G tolerance or G endurance. The aim of this study was to investigate the effects of chest counterpressure on the work of breathing and the risk for lung rupture. METHODS: Eight male test subjects were exposed to 20-s periods of PPB at +1.0, 5.0, 6.0, 7.0, and 8.0 Gz. Each Gz level was accomplished twice, with and without pressurization of the chest bladder. Inspiratory and expiratory flows were measured and esophageal pressures were measured in the lower and upper third of the thorax. Subsequently, work and power of breathing and apical transpulmonary pressure were estimated. RESULTS: The apical transpulmonary pressure was slightly larger without than with chest counterpressure at 1.0 Gz, while chest counterpressure did not affect apical transpulmonary pressure at increased Gz load. Nor did the chest counterpressure affect work or power of breathing at any Gz load. CONCLUSION: Inflation of the chest bladder does not seem to have any effects on work or power of breathing or risk for lung rupture during PPB at high Gz loads.
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| 9. |
- Levin, Britta, et al.
(författare)
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Memory performance during G exposure as assessed by a word recognition task
- 2007
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 78:6, s. 587-592
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Tidskriftsartikel (refereegranskat)abstract
- Background: Pilots of modern fighter aircraft are exposed to substantial physiological and mental stressors. The objective of this study was to investigate how memory performance, in terms of encoding and/or retrieval processes, was affected by sustained +Gz exposure. Method: There were 18 healthy men ranging from experienced fighter pilots to novice riders who participated. A word continuous recognition task (CRT) was employed as a memory test. The task consisted of three consecutive phases: 1) encoding of familiar words at 1 G, 2) encoding and retrieval of words at 70% of the subject's relaxed G-tolerance level, equivalent to +3.7 ± 0.54 Gz, and 3) encoding and retrieval of words at 1 G. In addition, each subject performed the CRT in a 1-G-only control condition. Physiological and psycho-physiological measures included continuous monitoring of ECG, arterial oxygen saturation, arterial BP at head level, and response time. Results: Data analysis showed that the capability to recognize words encoded at 1 G did not differ between conditions, indicating that the retrieval process was insensitive to increased Gz load. However, the ability to recognize words previously encoded during G exposure was reduced by approximately 10% as compared with control. Since the analysis revealed that the words were perceived, this result suggests that the encoding process was impaired in hypergravity. Conclusion: The results indicate that memory encoding, but not retrieval, was affected negatively when exposed to substantial and sustained +Gz loads. Copyright © by Aerospace Medical Association.
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| 10. |
- Lindgren, Torsten, et al.
(författare)
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Perception of cockpit environment among pilots on commercial aircraft
- 2006
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 77:8, s. 832-837
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Tidskriftsartikel (refereegranskat)abstract
- Impaired cockpit environment may influence both well-being and performance of pilots. Objective: To study the perception of cockpit environment among pilots, in relation to demographic factors, and type of air craft (B767-300, B737-600, DC9/21-41, MD 81/90 series). Methods: A standardized questionnaire was mailed to all pilots in one airline company; 81% participated (n = 622). All flights were non-smoking flights and the B767 was the only aircraft operated on intercontinental flights. The DC9 was the only aircraft without air recirculation. Multiple logistic regression analysis was applied, controlling for age, gender, smoking, perceived psychosocial work environment, and type of aircraft. Results: Younger age and a history of atopy and stress due to excess work were the main predictors of symptom and environmental perceptions. The most common symptoms were fatigue (14%), facial dermal (10%), and nasal symptoms (9%). Common complaints on cockpit environment were dry air (53%), dust and dirt (48%), noise (46%), and inadequate illumination (34%). Using the DC9 as a reference category, Boeing 767 pilots had more fatigue (OR 19.5; p < 0.001), throat symptoms (OR = 4.40; p < 0.05), complaints on dry air (OR = 2.93; p < 0.01), stuffy air (OR = 4.60; p < 0.01), static electricity (OR = 6.39; < 0.05), and dust (OR = 2.01; p < 0.05). Boeing 737 pilots had more complaints on noise (OR = 4.01; p < 0.001) and dust (OR = 1.81; p < 0.05). MD 81/90 pilots had more complaints on dry air (OR = 1.76; p < 0.05), dust (OR = 1.92; p < 0.05), and inadequate illumination (OR = 2.08; p < 0.05). Conclusion: Complaints on the cockpit environment were common and differed between different types of aircraft. This indicates a need to optimize the cockpit environment, e.g., increase the cleaning and relative air humidity.
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