Why heart function is reduced at high altitude decoded

Scientists have found why high altitudes reduces the amount of blood the heart pumps around the body with each beat.

The research, published in The Journal of Physiology, will be important for people who live, travel and exercise at high altitudes, scientists said.

Over the years, several theories have been proposed to explain the reduction in the amount of blood the heart can pump; this was even of interest to the scientists involved in the first summit of Mount Everest in the 1950's.

Researchers including those from the Cardiff Metropolitan University in the UK and University of British Columbia in Canada showed that at high altitudes (over 3000 metres), the lower amount of oxygen in the air leads to a decrease in the volume of blood circulating around the body, and an increase in blood pressure in the lungs.

They found that both of these factors play a role in the reduction in the volume of blood the heart can pump with each beat, but importantly neither of these factors affects our ability to perform maximal exercise.

This research is important because it improves our understanding of how the human body adapts to high altitude areas.

This will help us make exploration and tourism of Earth's mountainous regions safer, and may also help facilitate exercise performance in a wide range of sporting events that take place at high altitude.

"Currently, a number of the research team are ready to depart for an expedition that will focus on high altitude natives who live and work in the industrial mines of the Andean mountains," Michael Stembridge, the chief investigator on the project.

"Unfortunately, a third of these individuals experience long-term ill health due to their residence at high altitude, a condition termed 'Chronic Mountain Sickness'," Stembridge said.

"We hope to apply the findings of this work to help improve the health and well-being of these populations by furthering our understanding of the condition and exploring therapeutic targets," he said.

It is important to note that the sample size of this study was small and the effects of these mechanisms were only compared in individuals of European descent, researchers said.

Furthermore, echocardiography was used to assess cardiac and pulmonary vascular function which is non-invasive and indirect.