Oxygen Supplementation Improves Oxygen Uptake Kinetics and Exercise Performance in PAH and CTEPH Patients.

Abstract

Aim: We studied the effect of O₂ supplementation on physiological responses to exercise in patients with pulmonary vascular disease.

Methods: Six patients with pulmonary arterial hypertension (PAH), four patients with chronic thromboembolic pulmonary hypertension (CTEPH) (age 54 ± 17 years; 8 females) and 13 healthy individuals (age 50 ± 17 years; 5 females) were tested. PAH/CTEPH was defined hemodynamically by mPAP > 20 mmHg and PVR > 3 WU. Patients performed symptom-limited cardiopulmonary exercise tests, and constant work-rate tests (CWRTs) at 80% of the work-rate (WR) at the gas exchange threshold (GET). Tests breathing room air (RA, 21% O₂) were compared to tests performed breathing 30% O₂. Oxygen-uptake (V̇O₂) kinetics were calculated from the CWRT results.

Results: In the PAH/CTEPH group, peak WR, peak V̇O₂ and V̇O₂ at the GET improved significantly when breathing 30% O₂ compared to RA (mean ± SD 85 ± 26 vs. 77 ± 25 W, 18.3 ± 5.8 vs. 15.6 ± 5.7 mL/kg/min and 764 ± 181 vs. 685 ± 154 mL/min; p = 0.011, p = 0.015 and p = 0.012, respectively). Peak V̇O_2/HR was higher with 30% O₂ compared with RA (8.8 ± 2.2 vs. 7.7 ± 1.8 mL/beat, p = 0.021). The time constant (tau) of V̇O₂ kinetics was faster in PAH/CTEPH patients while breathing 30% O₂ compared to RA (36 ± 4 vs. 43 ± 6 s, p = 0.009). In healthy individuals there was no improvement in V̇O₂ kinetics while breathing 30% O₂ compared to RA (tau 35 ± 6 vs. 35 ± 6 s, p = 0.916).

Conclusion: A clinically applicable level of O₂ supplementation (30%) improved maximal and aerobic exercise capacity and V̇O₂ kinetics in PAH/CTEPH patients. O₂ supplementation may be considered to support exercise training in PAH/CTEPH patients.