Effect of High Altitude Exposure, Acclimatization and Re-exposure on Cerebral Autoregulation in Lowlanders

Effect of High Altitude Exposure, Acclimatization and Re-exposure on Cerebral Autoregulation in Lowlanders

Effect of High Altitude Exposure, Acclimatization and Re-exposure on Cerebral Autoregulation in Lowlanders

Prospective interventional trial in lowlanders evaluating the effect of acute exposure, acclimatization and re-exposure to high altitude on cerebral autoregulation

Baseline measurements will be performed in Santiago de Chile, 520 m, over the course of 3 days. Participants will then travel by commercial airline (5 h flight) and by bus (3 h ride) to the ALMA base camp located at 2900 m near San Pedro de Atacama, northern Chile. Participants will stay there for the next 8 nights and they will be spend the days (6-8 h daily) at the telescope station at 5050 m while undergoing testing as described above at the first and the last day at 5050m. Daily transports from 2900 to 5050 m will be by car (1 h ride, one way). After the first 8 day altitude sojourn participants will return to the Santiago area (520 m) for a 6 day recovery period. A second altitude sojourn with an identical schedule as the one described above and a final low altitude stay of 3 days will follow.

Acute high altitude exposure followed by 8 day acclimatization and reexposure for 8 days after 6 days at low altitude

Coherence between middle cerebral artery blood flow velocity and systemic blood pressure as measure of cerebral autoregulation.

Change in magnitude of the coefficient of coherence between blood flow velocity in the middle cerebral artery measured by transcranial ultrasound Doppler and systemic blood pressure at day 2 (5050 m) vs. day 1 (520 m) of the first cycle

Coherence between middle cerebral artery blood flow velocity and systemic blood pressure as measure of cerebral autoregulation.

Change in magnitude of the coefficient of coherence between blood flow velocity in the middle cerebral artery measured by transcranial ultrasound Doppler and systemic blood pressure at day 7 (5050 m) vs. day 1 (520 m) of the first cycle.

Coherence between middle cerebral artery blood flow velocity and systemic blood pressure as measure of cerebral autoregulation.

Change in magnitude of the coefficient of coherence between blood flow velocity in the middle cerebral artery measured by transcranial ultrasound Doppler and systemic blood pressure at day 7 (5050 m) vs. day 2 (5050 m) of the second cycle.

Coherence between middle cerebral artery blood flow velocity and systemic blood pressure as measure of cerebral autoregulation.

Change in magnitude of the coefficient of coherence between blood flow velocity in the middle cerebral artery measured by transcranial ultrasound Doppler and systemic blood pressure at day 2 (5050 m) second cycle vs. day 2 (5050 m) of the first cycle.

Coherence between middle cerebral artery blood flow velocity and systemic blood pressure as measure of cerebral autoregulation.

Change in magnitude of the coefficient of coherence between blood flow velocity in the middle cerebral artery measured by transcranial ultrasound Doppler and systemic blood pressure at day 7 (5050 m) second cycle vs. day 7 (5050 m) of the first cycle.

Inclusion Criteria: Born, raised and currently living <800m No overnight stay at altitudes >1500 m 4 weeks before the study Exclusion Criteria: Previous altitude intolerance to altitude <3000 m Pregnancy Health impairment, which requires regular treatment