Abstract
BACKGROUND: Exercise training for patients with chronic obstructive pulmonary disease (COPD) improves their endurance and oxygenation. Supplemental oxygen delivered by high flow nasal cannula (HFNC) reportedly improves the clinical outcomes during high-intensity exercise. However, the physical benefits of the provision of supplemental oxygen with HFNC for the improvement of exercise performance have not been fully investigated. This randomized trial aimed to evaluate the effect of HFNC on the hemodynamic status and peripheral muscle microcirculation during exercise training. METHODS: In this multicenter, randomized controlled parallel two-group study, 32 patients with moderate to severe COPD were randomly assigned into the nasal cannula (NC) group (n=15) with a flow rate of 2-3 L/min or the HFNC group (n=17) with a flow rate of 45 L/min for twelve 40 min exercise training sessions. RESULTS: The mean cardiac index (CI) and stroke volume (SV) of the NC group in the first session were significantly lower than those of the HFNC group (3.68±0.76 vs. 4.5±0.76 L/min/m(2), P=0.014; 63.03±9.87 vs. 74.22±19.48, P=0.002, respectively). The systemic vascular resistance (SVR) of the NC group was significantly lower in the seventh session than in the first session (891±287 vs. 1,138±381 dyn-s/cm(5), respectively, P=0.048). The mean deoxyhemoglobin level was higher in the HFNC group in the 1(st) session and lower in the 12(th) session (1.09±9.04 vs. 7.3±7.3 µm, P=0.046). The COPD Assessment Test score, Modified Medical Research Council scale score, maximum inspiratory pressure (MIP), and maximum expiratory pressure were different within and between the groups. CONCLUSIONS: HFNC, with a lower oxygen concentration than that used with a traditional NC, yielded lower deoxygenated hemoglobin levels after 12 suboptimal exercise training sessions. In contrast, the higher oxygen concentration delivered by NC reduced SVR. The COPD assessment score improved on exercise training, regardless of the supplemental oxygen delivery method.