Blood pressure vs altitude in hypertensive and non-hypertensive himalayan trekkers

Philadelphia

Introduction: Determine blood pressure (BP) response to changes in altitude in Himalayan trekkers with and without hypertension (HTN). Methods: BP was measured in Lukla (2800m), Namche (3400m), and either Pheriche or Dingboche (4400m) on ascent and descent. Hypertensive subjects were defined by self-reported diagnosis of HTN. Results: Trekkers had HTN (H, n=60) or no HTN (NH, n=604). Of those with HTN, 50 (83%) took one or more BP medications including ACEIs/ARBs (n=35, 48%), Ca++ channel blockers (n=15, 22%), beta-blockers (n=9, 13%), thiazide diuretics (n=7, 10%), and others (n=5, 7%). At 2800m, systolic BP (SBP) and diastolic BP (DBP) were greater in the H group than in the NH group [mean SBP= 151mmHg (95% CI 145.4-155.7) vs 127mmHg (95% CI 125.5 128.0); mean DBP=88mmHg (95% CI 85.1-91.7) vs 80mmHg (95% CI 79.3-80.8)] and remained higher at both 3400m [mean SBP=150mmHg (95% CI 143.7-156.9) vs 127mmHg (95% CI 125.8-128.5); mean DBP=88mmHg (95% CI 84.3-90.8) vs 82mmHg (95% CI 80.7-82.5)] and 4400m [mean SBP=144mmHg (95% CI 136.7-151.7) vs 128mmHg (95% CI 126.4-129.5); mean DBP=87mmHg (95% CI 83.2-91.7) vs 82mmHg (95% CI 81.3-83.2)]. Between 2800m and 3400m, BP increased in 37% of trekkers, decreased in 25%, and did not change in 38%; from 3400m to 4400m, BP increased in 35% of trekkers, decreased in 26%, and did not change in 40%. Prevalence of severe hypertension (BP>180/120mmHg) was similar across altitudes but higher in the H group (9%; 10%; 8% vs 0.7%; 0.6%, 0.3%) at 2800m, 3400m, and 4400m, respectively. No subjects reported symptoms of hypertensive emergency (chest pain, stroke, etc.). Conclusion: Blood pressure response to altitude is variable. High prevalence of severe hypertension in hypertensive trekkers warrants further study regarding BP control at high altitude.