Introduction
For those traveling to high altitude, it has been postulated that blood pressure (BP) changes when compared to sea level. Also at altitude, periodic breathing has been well described and is correlated to decreased sleep quality.
Objective
Measure continuous sleeping and awake blood pressures in both normotensive and hypertensive Himalayan trekkers.
Methods
Blood pressure was measured with Welch-Allyn 6100 24h ambulatory BP monitors (24h-ABPM) every 30 minutes while awake and every 60 minutes while asleep. Baseline demographic data were obtained on arrival at 2860 m and 24h-ABPM measured between 2860 to 3440 m and 3440 to 4400 m. Hypertensive subjects were defined by self-reported diagnosis of hypertension (HTN). Acute mountain sickness was measured by Lake Louise Score (LLS).
Results
Eight subjects were enrolled, 4 with pre-existing treated HTN. Data were insufficient or incomplete for 2 subjects with HTN. Between 2860 and 3400 m, the 4 normotensive subjects (NTN) had the expected decrease in BP during sleep. Mean arterial pressure (MAP) decreased from an average of 95 mm Hg (95% CI, 89.76–100.24 mm Hg) while awake to 82.5 mm Hg (95% CI, 74.72–90.28 mm Hg). The 2 with HTN had an increase in BP from awake hours (95.5 mm Hg [95% CI, 84.81–106.11 mm Hg]) to sleep (112.5 mm Hg [95% CI, 100.48–124.52 mm Hg]). The observed pattern in awake vs sleeping BP was similar between 3440 and 4400 m, (N = 4, 3 NTN, 1 HTN). The NTN had an average awake MAP of 94.67 mm Hg (95% CI, 90.1–99.24 mm Hg) that decreased to 86 mm Hg (95% CI, 74.03–97.97 mm Hg) and the HTN subject had an increase from awake MAP (90 mm Hg) to sleep MAP (106 mm Hg). No subject developed AMS at any altitude. No differences in heart rate, maximum or minimum BP, or number of BPs above normal were found between NTN and HTN groups at altitude.
Conclusions
These findings suggest that those with baseline HTN may have an increase in BP while sleeping compared with NTN individuals at high altitude. The clinical significance of these findings remains to be studied.
Funding
WMS Hultgren Grant (2015); Nepal International Clinic.