Study examines role of low-oxygen exposure in heart failure patients

Distance runners who live at high altitudes with low oxygen levels are known to improve their performance during races in areas that are at sea level. Can heart failure patients, who suffer from fatigue, improve their exercise performance by staying in a tent-like, high-altitude simulator?

That is the question being studied among 15 heart failure patients at Montefiore Medical Center. "The goal of the FDA-approved study is to see if high altitude simulation is safe and feasible for heart failure patients. And, more specifically, will low-oxygen exposure improve their skeletal muscle function, cardiac function and exercise capacity," said Simon Maybaum, MD, medical director of the Montefiore-Einstein Center for Advanced Cardiac Therapy.

"It seems counterintuitive to put heart failure patients in a low-oxygen tent to improve their performance," said Dr. Maybaum. "But, we know that athletes, as they acclimate to an oxygen-low environment, benefit physiologically. In just a few weeks, they show improvement in the oxygen carrying capacity of their blood, in tissue oxygenation and in physical performance. We want to see if similar physiological changes would be beneficial to heart failure patients," he said.

The Montefiore study will enroll stable, chronic heart-failure patients whose ability to exercise is limited despite maximal conventional therapies. They will sit in tents during 10 high-altitude sessions over 22 days, with each session lasting three to four hours. The oxygen inside the tent will be adjusted slowly to mimic the amount of oxygen at 1,500 meters and gradually increased to 2,700 meters (1.7 miles high), slightly above the pressurization of an airplane cabin. Then they will be tested to see how acclimatization to low oxygen in the tent has affected their exercise performance.

Dr. Maybaum, who is a marathoner, has previously studied how his chronic heart failure patients can benefit from other performance enhancing techniques used by athletes, including the muscle bulking drug clenbuterol. He found that clenbuterol increased their skeletal muscle mass and strength, but not their endurance. Among other things, he wants to determine if exposure to the high-altitude simulator will improve patients' endurance.