The effect of altitude on blood pressure has been found for the first time by researchers in a new Mount Everest expedition.
The study showed that blood pressure monitored over a 24-hour period rises progressively as people climb to higher altitudes. The researchers also found that while a drug used for lowering blood pressure, called telmisartan, was effective in counteracting the effects of altitude up to 3400 metres, it was not effective at 5400 metres above sea level - the height of the Everest base camp.
The findings have implications not just for people who live, work or undertake recreational
activities such as skiing and trekking at high altitudes, but also for people at lower altitudes who may be temporarily deprived of an adequate oxygen supply, a condition known as hypoxia.
Professor Gianfranco Parati, of cardiovascular medicine at the University of Milano-Bicocca, said that The blood pressure increase was due to several factors, the most important being the effects of oxygen deprivation in increasing activity in the body's sympathetic nervous system and this leads to the heart working harder and the peripheral blood vessels constricting.
He further explained for people already being treated with angiotensin II receptor blockers such as telmisartan, the treatment would remain effective at altitudes reached by trekkers, climbers, skiers and workers, but would not work at very high altitudes where their blood pressure would probably become uncontrolled more easily.
This study emphasized on the importance of ambulatory blood pressure monitoring as compared to conventional blood pressure measurements in characterising blood pressure levels in people's real lives; this is particularly important when focusing on the effects of hypoxia, which can be much less evident at rest than during daily life activities.
The study is published in the European Heart Journal.