Health, Exercise, and Sports Sciences ETDs

Publication Date

Summer 7-13-2020

Abstract

The purpose of this study was to determine whether there is a difference in hemodynamic responses to head-up tilt (HUT) in subjects who do, and do not, experience acute mountain sickness (AMS) during exposure to hypobaric hypoxia. Secondarily, we aimed to determine if those hemodynamic variables altered during HUT correlated with AMS severity. Fifteen participants completed three testing sessions: 1) VO2max test to determine workload at 50% VO2max for hypoxia exposure; 2) HUT test consisting of supine rest for 20 min followed by 70° upright tilting for ≤ 40 min; and 3) six hours of hypobaric hypoxic exposure simulating 4572 m where participants performed two, 30 min cycling bouts and rested when not exercising. During HUT, continuous blood pressure monitoring was used to assess systolic and diastolic blood pressure (SBP & DBP), mean arterial pressure (MAP), variability in SBP, DBP, and MAP, and heart rate. AMS scores were determined before and after six hours of hypoxic exposure. Statistical analysis included mixed effects ANOVA to determine changes between supine rest and end of HUT and between selected AMS positive (AMS+) and AMS negative (AMS-) groups. Correlations by linear regression determined associations between HUT hemodynamic responses and AMS scores. Statistical significance was set to p < 0.05. Those with higher AMS scores tended to have a greater magnitude of change in SBP, DBP, and MAP variability during the HUT test (r = 0.65, 0.64, & 0.60, respectively). Increased blood pressure variability (BPV) indicated a disruption in blood pressure regulation, suggesting that AMS+ individuals may have a disruption in their blood pressure regulation. This increases their susceptibility which could be observed during a postural change prior to hypoxic exposure. In conclusion, BPV during HUT may be a promising predictive variable for AMS but further research is needed. In the future, researchers should consider using sea-level living participants and a range of simulated elevations to determine the predictability of AMS-susceptibility by BPV.

Keywords

hypoxia, head-up tilt test, blood pressure variability

Document Type

Dissertation

Language

English

Degree Name

Physical Education, Sports and Exercise Science

Level of Degree

Doctoral

Department Name

Health, Exercise, and Sports Sciences

First Committee Member (Chair)

Christine Mermier, PhD

Second Committee Member

Jack Loeppky, PhD

Third Committee Member

Ann Gibson, PhD

Fourth Committee Member

Scott Drum, PhD

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