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

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

Detailed Description
-----------------
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.

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

Conditions
-----------------
Effect of High Altitude

Intervention / Treatment
-----------------
* Other: altitude exposure


Participation Criteria
=================
Eligibility Criteria
-----------------
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

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Prevention
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Altitude exposure<br>Acute high altitude exposure followed by 8 day acclimatization and reexposure for 8 days after 6 days at low altitude | Other: altitude exposure<br>* altitude exposure<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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 | day 1; day 2 first cycle | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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. | day 1; day 7 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. | day 2; day 7 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. | day 2 first cycle; day 2 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 7 (5050 m) second cycle vs. day 7 (5050 m) of the first cycle. | day 7 first cycle; day 7 second cycle | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
High altitude, Cerebral autoregulation, Transfer function analysis