Aviat Space Envir Md
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Aviat Space Envir Md · Feb 2003
Air transport of patients with intracranial air: computer model of pressure effects.
Air is commonly trapped within the skull in patients who have been treated for trauma or intracranial hemorrhage. In Sweden, when such a patient is transported by air ambulance it is standard procedure to maintain sea-level pressure in the cabin to prevent increased intracranial pressure (ICP). However, this type of flight operation is more difficult and expensive. Maintenance of sea-level cabin pressure is not common practice all over the world, and the criteria supporting the choice of pressurization during transport are inadequate and in need of evaluation. The purpose of this study was to develop and evaluate a model to simulate the influence of intracranial air on ICP during air transport. ⋯ Our results support the need for maintenance of sea-level pressure during air transport of patients with suspected intracranial air, since an ICP increment could potentially impair the patient's clinical condition.
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Aviat Space Envir Md · Feb 2003
The effect of posture and positive pressure breathing on the hemodynamics of the internal jugular vein.
Mathematical and mechanical models of cerebral circulation indicate that the resistance of the collapsed internal jugular veins limits cerebral blood flow during high acceleration (+Gz) and that positive pressure breathing (PPB) restores cerebral blood flow by elevating blood pressure and preventing collapse of the vein. The effect of acceleration and PPB on the jugular resistance and flow can be estimated by documenting changes in the lumen area and blood velocity. ⋯ The results demonstrate that the internal jugular vein collapses with transition from supine to sitting position. This implies a significant increase in resistance which is inversely proportional to the square of the lumen area. However, the collapse can be prevented with sufficiently high PPB.
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Aviat Space Envir Md · Feb 2003
In-flight hypoxia incidents in military aircraft: causes and implications for training.
Hypoxia has long been recognized as a significant physiological threat at altitude. Aircrew have traditionally been trained to recognize the symptoms of hypoxia using hypobaric chamber training at simulated altitudes of 25,000 ft or more. The aim of this study was to analyze incidents of hypoxia reported to the Directorate of Flying Safety of the Australian Defence Force (DFS-ADF) for the period 1990-2001, as no previous analysis of these incidents has been undertaken. The data will be useful in planning future training strategies for aircrew in aviation physiology. ⋯ This study confirms the importance and effectiveness of hypoxia training for aircrew. Hypoxia incidents occur most commonly at altitudes less than 19,000 ft. This should be emphasized to aircrew, whose expectation may be that it is only a problem of high altitude. Proper fitting of masks, leak checks, and equipment checks should be taught to all aircrew and reinforced regularly. Current hypobaric chamber training methods should be reviewed for relevance to the most at-risk aircrew population. Methods that can simulate subtle incapacitation while wearing oxygen equipment should be explored. Hypoxia in flight still remains a serious threat to aviators, and can result in fatalities.