Altitude simulator improves exercise performance and QoL measures in heart-failure patients

November 16, 2011

Orlando, FL - Elite marathoners and cyclists might train in Colorado for the altitude, but a new study suggests that even heart-failure patients could benefit from a hypoxic environment. New data from a small pilot study showed that simulated altitude training appears to be a safe and effective treatment option in heart-failure patients, with altitude exposure resulting in significant and sustained improvements in exercise performance, skeletal-muscle strength, and quality-of-life measurements.

In the study, presented here at the American Heart Association 2011 Scientific Sessions , the researchers, led by Dr Simon Maybaum (Montefiore Medical Center, New York), tested an enclosed altitude simulator in 12 patients with stable heart failure. Altitude training, as well as simulating hypoxic environments, has been popularized by athletes, particularly endurance athletes, looking to gain an edge over their opponents.

"As a group, we have been looking for ways to potentiate exercise performance in patients with stable heart failure, recognizing that's one of the primary targets of therapy and one of the best ways to improve their quality of life," Maybaum told heartwire . "We have taken the approach that there may be ways that we can borrow from approaches used by athletes to improve their skeletal-muscle strength and performance."

In this study, the researchers tested the effectiveness of "normobaric hypoxia" with an enclosed altitude simulator, a portable system made by Hypoxico (New York, NY), in 12 individuals with stable chronic heart failure. The patients underwent 10 sessions over a three-week period, and each session in the altitude simulator lasted between three and four hours. The starting altitude was the equivalent of 1500 m, and this was increased by 300 m with each session to a maximum of 2700 m. In normobaric hypoxia, atmospheric-pressure levels remain normal but oxygen levels are reduced.

Altitude exposure improved exercise times, the six-minute-walk test, and quality-of-life scores 48 hours after the completion of treatment, and these improvements were sustained when assessed again four weeks after the study's completion. There was a trend toward increased red blood cell mass and peak VO2, while left ventricular ejection fraction also was higher 48 hours and four weeks after the study was completed.

Results 48 hours and four weeks after study completion

Variable Baseline 48 h after completion of last session 4 wk after the completion of last session p (48 h vs baseline) p (4 wk vs baseline)
Left ventricular ejection fraction (%) 31.7 34.4 36.1 0.121 0.054
Peak VO2 (mL/kg/min) 13.5 14.2 14.5 0.036 0.123
Exercise test (s) 615.5 677.9 682.3 0.028 0.023
6-min-walk test (m) 387.4 415.3 441.1 0.013 0.003
Red blood cell mass (mL/µL) 4.38 4.43 4.51 0.110 0.158
Minnesota Living with Heart Failure score 33.75 24.09 22.55 0.00034 0.027
Maximal volume contraction, bicep (lbs) 56.70 62.15 62.47 0.039 0.016

To heartwire , Maybaum explained that one of the benefits of altitude training is an enhanced delivery of oxygen to the periphery, and this is one of the major deficits in patients with heart failure.

"Only a small part of why patients get breathless and have exercise intolerance in heart failure is that their heart is weak," said Maybaum. "Much of it is because their muscles and the blood vessels to the muscles do not work efficiently. The muscles aren't efficient at taking up the oxygen, so we believe that borrowing an approach that improves oxygen delivery to the periphery would be very helpful."

The Food and Drug Administration granted approval of the study because while the enclosed simulator is available for athletes, it is not approved for patients. Maybaum said that for the device to be practical, the goal would be for patients to sleep at home using the system. He suspects that to maximize the effects of altitude simulation, a combination of therapy with altitude and exercise would be needed, similar to how athletes gain the benefits of acclimatization. Future studies will include testing a strategy of exercising under simulated altitude conditions.

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