The latest results from an expedition to Mount Everest that looked at the body’s response to low oxygen levels suggest that drugs or procedures that promote the body’s production of nitric oxide (NO) could improve the recovery of critically ill patients in intensive care. The findings, published in Scientific Reports, suggest that interventions to alter NO production—some of which already exist in the form of drugs and gas—may benefit critically ill patients in whom oxygen availability is limited.
Using blood samples and data collected during the 2007 Caudwell Xtreme Everest (CXE) expedition, British researchers found that NO production and activity are elevated in people living near sea-level altitudes (lowlanders) who ascend to altitude, leading to changes in blood flow in the smallest blood vessels. This is the first time such effects have been documented in a larger group of lowlanders and is consistent with earlier data from residents of the Tibetan plateau (highlanders) showing their normal NO levels to be much elevated compared to people living near sea level.
Doctors believe increased NO may be beneficial for people, particularly patients with low levels of oxygen in their blood, because it increases the body’s ability to tolerate and adapt to a low oxygen supply.
The study participants consisted of 198 trekkers and 24 climbers, including doctors and scientists. The CXE team made the first-ever measurement of the oxygen level in human blood at 8,400 m on Mount Everest. This data was the centerpiece of an extensive and continuing research study into hypoxia and human performance at extreme altitude aimed at improving the care of critically ill and other patients where hypoxia is a fundamental problem.
“Climbing to extreme altitudes puts the body in an environment with very low oxygen availability, similar to the experience of patients in intensive care with diseases affecting the heart, lungs, or vascular system,” said Dr. Denny Levett, joint lead author of the study from University College London, and deputy research lead of the CXE expedition. “By taking blood samples from hypoxic, but otherwise healthy, individuals we have been able to show that the body’s natural response to low oxygen availability is to increase the production of nitric oxide. Thus, elevated NO occurs not just in those who live at high altitudes permanently, but also in lowlanders who are trying to adapt to high altitude conditions.”
According to Martin Feelisch, joint lead author and professor of experimental medicine and integrative biology at the University of Warwick Medical School, these findings suggest that “there is an alternative way of alleviating the consequences of low oxygen levels by creating a more sustained tolerance to those low levels through treatments which boost NO production.”
The researchers also found a difference between individuals in terms of the level of their NO response at altitude. While the sample size is too small to say with confidence why this is, individuals with greater experience of climbing at altitude had a greater NO response early in the expedition, suggesting their bodily constitution with respect to NO was different from climbers with less experience of ascent to high altitude. Similar factors may explain the differences in disease outcome between patients in intensive care.
Source: University of Warwick