It has been known for some time that both tadalafil and dexamethasone (dex) are good for preventing high altitude pulmonary edema (HAPE) and dex is also good for treating symptoms of acute mountain sickness.

What researchers did not know and were keen to find out, was whether they could also improve exercise capacity at altitude by reducing pulmonary hypertension, one of the important factors in altitude-related exercise limitations.

Their results were published in the August 15th issue of the the American Journal of Respiratory and Critical Care Medicine, the journal of the American Thoracic Society.

The researchers recruited 23 mountaineers with a history of high altitude pulmonary edema and administered baseline cardiopulmonary exercise tests at a low elevation, followed by a second round of cardiopulmonary exercise tests, performed 4-5 hours after an ascent to 4,599 meters and echocardiographic examinations performed the next day. All participants were randomised to take either tadalifil, dexamethasone or a placebo.

“Reduced oxygen content in the air is the major limiting factor at high altitude. Reduction in exercise capacity goes in parallel to the reduction in oxygen up to an altitude of approximately 4000 meters. At higher altitudes, there is an even further reduction in exercise capacity,” said researcher Dr. Fischler. “As expected, exercise capacity at high altitudes was diminished among all groups and key indicators of cardiopulmonary stress were elevated.”

Both tadalafil and dexamethasone subjects showed a smaller drop in oxygen saturation over the placebo group, indicating a better uptake of oxygen and a measure of pulmonary artery pressure was significantly less for both tadalifil and dexamethasone groups over placebo.

“In this study, we found that the most important limiting factor, with respect to exercise capacity at high altitude, is primarily pulmonary hypertension – elevated blood pressure in the circulation of the lungs – which may further reduce the oxygen uptake, particularly during exercise.

Our study indicates that for HAPE-susceptible climbers, taking dexamethasone improved exercise capacity, oxygen uptake kinetics and decreased the anaerobic threshold,” said Dr. Fischler.

“Overall, this means that those climbers who took dex felt better, were able to do more, and probably experienced fewer altitude-related discomforts than both other groups.”

Source: American Journal of Respiratory and Critical Care Medicine