Exercise Performance of Lowlanders with COPD at 2,590 m: Data from a Randomized Trial

Area of Science:

• Environmental Physiology
• Pulmonary Medicine
• Exercise Science

Background:

• The impact of hypobaric hypoxia at altitude on exercise performance in lowlanders with chronic obstructive pulmonary disease (COPD) remains understudied.
• Understanding these effects is crucial for managing COPD patients who travel to or live at higher altitudes.

Purpose of the Study:

• To quantify the changes in exercise performance in lowlanders with COPD when ascending to moderate altitude.
• To assess associated physiological responses, including systemic and cerebral oxygenation, during exercise at different altitudes.

Main Methods:

• Thirty-one lowlanders with COPD performed constant-load bicycle exercise to exhaustion at 490 m and 2,590 m in a randomized order.
• Measurements included pulmonary gas exchange, pulse oximetry (SpO2), cerebral tissue oxygenation (CTO) via near-infrared spectroscopy, and middle cerebral artery peak blood flow velocity (MCAv) using Doppler ultrasound.

Main Results:

• Exercise endurance time was significantly reduced by over 50% at 2,590 m compared to 490 m (500 s vs. 205 s).
• Ascent to 2,590 m led to decreased SpO2 (92% to 81%) and CTO (62% to 55%), with increased minute ventilation.
• While middle cerebral artery blood flow velocity increased similarly at both altitudes, the ratio of MCAv increase to SpO2 drop was lower at 2,590 m, indicating impaired cerebral blood flow regulation.

Conclusions:

• Moderate altitude significantly impairs exercise endurance in lowlanders with COPD, reducing it by more than half compared to sea level.
• This reduction is linked to decreased systemic oxygen saturation and cerebral oxygen availability, highlighting the challenges faced by COPD patients at altitude.