Cerebral Vascular Response in Airmen Exposed to Hypobaric Hypoxia
| Autor: | Edoardo Vicenzini, G Ciniglio Appiani, Anton G. Guadagno, Leonardo Davì, Enrico Tomao, Fabio Morgagni |
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| Rok vydání: | 2011 |
| Předmět: |
Adult
Male Atmosphere Exposure Chambers Middle Cerebral Artery medicine.medical_specialty Ultrasonography Doppler Transcranial Diastole Vasodilation Altitude training Internal medicine Humans Medicine Hypoxia Hypoxia Brain business.industry Altitude Public Health Environmental and Occupational Health Brain Blood flow Middle Aged Effects of high altitude on humans Hypoxia (medical) Transcranial Doppler Cerebrovascular Circulation Pulsatile Flow Hypobaric chamber Aerospace Medicine Cardiology medicine.symptom business Blood Flow Velocity |
| Zdroj: | Aviation, Space, and Environmental Medicine. 82:1138-1142 |
| ISSN: | 0095-6562 |
| DOI: | 10.3357/asem.3079.2011 |
| Popis: | Introduction Cerebral vascular response via local and reflex adjustments is part of the integrated response to hypoxia and is coupled with changes in systemic vascular resistances that allow a redistribution of blood flow toward the brain. The cerebral vascular response in airmen exposed to simulated high altitude is not clear, thus we sought to investigate this aspect. Methods Four healthy military airmen were exposed to simulated high altitude in a hypobaric chamber according to a standard training protocol. Blood saturation (SpO2) and blood flow velocity with transcranial Doppler from the left middle cerebral artery (Vm) were continuously recorded. Pulsatility Index (PI), resistance index (RI), and systolic/diastolic ratio (S/D ratio) were computed. Alternate hypoxia-hyperoxia trials for 2 and 1 min, respectively, were used to assess the cerebrovascular response. Results Acute hypoxia induced an increase in Vm that promptly recovered when the oxygen supply was restored (mean increase of 5.5% at 18,000 ft and 17.2% at 25,000 ft). Alternate hypoxia-hyperoxia at 25,000 and 18,000 ft elicited changes in both SpO2 and Vm. In hypoxia, PI significantly decreased (mean decrease o" 25.6% at 18,000 ft and 39.5% at 25,000 ft), as did RI (mean decrease of 18.7% at 18,000 ft and 34.4% at 25,000 ft), while S/D ratio increased. Discussion The standard altitude training protocol induced a transient cerebrovascular response. The response was as expected, with hypoxia-induced vasodilation and opposite changes when breathing pure oxygen. |
| Databáze: | OpenAIRE |
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