Exercise Performance of Lowlanders With COPD at 2,590 M: Data From a Randomized Trial

Respiration. 2018;95(6):422-432. doi: 10.1159/000486450. Epub 2018 Mar 2.

Abstract

Background: Effects of hypobaric hypoxia at altitude on exercise performance of lowlanders with chronic obstructive pulmonary disease (COPD) have not been studied in detail.

Objectives: To quantify changes in exercise performance and associated physiologic responses in lowlanders with COPD travelling to moderate altitude.

Methods: A total of 31 COPD patients with a median age (quartiles) of 66 years (59; 69) and FEV1 of 56% predicted (49; 69) living below 800 m performed a constant-load bicycle exercise to exhaustion at 60% of the maximal work rate at 490 m (Zurich) and at an identical work rate at 2,590 m (Davos) in randomized order. Pulmonary gas exchange, pulse oximetry (SpO2), cerebral tissue oxygenation (CTO; near-infrared spectroscopy), and middle cerebral artery peak blood flow velocity (MCAv) by Doppler ultrasound during 30 s at end exercise were compared between altitudes.

Results: With ascent from 490 to 2,590 m, the median endurance time (quartiles) was reduced from 500 s (256; 795) to 205 s (139; 297) by a median (95% CI) of 303 s (150-420) (p < 0.001). End exercise SpO2 decreased from 92% (89; 94) to 81% (77; 84) and CTO from 62% (56; 66) to 55% (50; 60); end exercise minute ventilation increased from 40.6 L/min (35.5; 47.8) to 47.2 L/min (39.6; 58.7) (p < 0.05; all comparisons 2,590 vs. 490 m). MCAv increased similarly from rest to end exercise at 490 m (+25% [17; 36]) and at 2,590 m (+21% [14; 30]). However, the ratio of MCAv increase to SpO2 drop during exercise decreased from +6%/% (3; 12) at 490 m to +3%/% (2; 5) at 2,590 m (p < 0.05).

Conclusions: In lowlanders with COPD travelling to 2,590 m, exercise endurance is reduced by more than half compared to 490 m in association with reductions in systemic and cerebral oxygen availability.

Keywords: Altitude; Chronic obstructive pulmonary disease; Exercise; Hypobaric hypoxia; Physiology.

MeSH terms

  • Aged
  • Altitude*
  • Cerebrovascular Circulation
  • Exercise Test
  • Exercise Tolerance*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pulmonary Disease, Chronic Obstructive / physiopathology*
  • Random Allocation