Key result
High altitude residents exhibit blunted orthostatic responses, increasing HR by only ~1 bpm upon standing.
Why the study?
Does altitude of residence influence orthostatic cardiovascular responses during high altitude exposure?
Cross-Sectional (n=69)
No
Does altitude of residence influence orthostatic cardiovascular responses during high altitude exposure?
p-value: p=<0.05
High altitude residents exhibit blunted cardiovascular responses to orthostatic stress and greater tolerance when exposed to high altitude compared to low and moderate altitude residents.
Findings should not yet alter clinical advice on altitude exposure; hypothesis-generating for acclimatization differences by residence.
This study evaluated the influence of altitude of residence on orthostatic responses when exposed to high altitude. Data collection took place at the Carrel hut (4860 m) on Chimborazo in Ecuador. After being transported to the hut by vehicle, 69 people volunteered for the study. A 3-min stand test (rapid change from supine to standing) provided an orthostatic challenge while resting heart rate (RHR), systolic (SBP) and diastolic (DBP) blood pressures, and arterial oxygen saturation (SpO2) were measured. Participants were separated into four groups based on altitude of residence and ethnicity: LOW (<1500 m; n=15), MOD (1500-3000 m, n=30), and HIGH (>3000 m, n=11) Ecuadorians, and non-Ecuadorian lowlanders (NE-LOW, n=13). Supine and standing RHRs were lower (p<0.05) for HIGH compared to other groups. Furthermore, standing increased RHR in LOW, MOD, and NE-LOW by 11.9 ± 5.3, 9.5 ± 4.1, and 11.6 ± 7.4 bpm, respectively, while HIGH stayed the same (0.6 bpm increase ± 3.3). Additionally, mean arterial pressure decreased slightly but not significantly upon standing in all groups except HIGH. The difference in Spo2 among groups was not significant (p>0.05). Altitude of residence influences the cardiovascular responses to orthostatic stress with HIGH having blunted responses and greater tolerance.
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Davis et al. (2013) conducted a cross-sectional in Healthy volunteers exposed to high altitude (n=69). High altitude of residence (>3000 m) vs. Low (<1500 m) and moderate (1500-3000 m) altitude residents, and non-Ecuadorian lowlanders was evaluated on Change in resting heart rate upon standing (p=<0.05). High altitude residents (>3000 m) exhibited blunted cardiovascular responses to orthostatic stress at 4860 m, with a minimal heart rate increase of 0.6 bpm upon standing compared to 9.5-11.9 bpm in lower altitude residents.
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