Supplementary Material for: Benefits of an Oxygen Reservoir Cannula versus a Conventional Nasal Cannula during Exercise in Hypoxemic COPD Patients: A Crossover Trial

<p><b><i>Background:</i></b> The Oxymizer® is a special nasal cannula that provides a higher luminal diameter in combination with an incorporated oxygen (O<sub>2</sub>) reservoir. It is assumed that a higher O<sub>2</sub> concentration can be delivered breath by breath in order to increase oxygenation. <b><i>Objective:</i></b> We aimed to investigate the effects of the Oxymizer on endurance time in comparison to a conventional nasal cannula (CNC). <b><i>Methods:</i></b> Forty-three patients with severe chronic obstructive pulmonary disease (COPD, age 60 ± 9 years, FEV<sub>1</sub> 37 ± 16% pred.) and indications for LTOT were recruited during pulmonary rehabilitation for this cross-over study. After an initial maximal incremental cycle test, all patients performed 4 cycling endurance time tests at 70% of their peak work rate (twice with the Oxymizer and twice with a CNC, in reverse order). <b><i>Results:</i></b> The endurance time was significantly higher when patients cycled while using the Oxymizer in comparison to while using the CNC [858 ± 754 vs. 766 ± 652 s; between-group difference 92 s (95% confidence interval 32-152), p < 0.001]. In addition to a longer cycling duration, O<sub>2</sub> saturation at isotime was significantly higher with the Oxymizer (93.5 ± 5.4 vs. 90.4 ± 5.3%; p = 0.027). Furthermore, there was a positive correlation (r = 0.427, p = 0.002) between the O<sub>2</sub> flow rate and improvements in the constant work rate test, showing greater improvements in favor of the Oxymizer in patients with a higher demand for O<sub>2</sub> (≥4 liters/min). <b><i>Conclusion:</i></b> We show that O<sub>2</sub> delivery via the Oxymizer is superior to a CNC with regard to endurance capacity and oxygenation during exercise in patients with severe COPD. It seems that patients with a higher demand for O<sub>2</sub> (≥4 liters/min), in particular, may benefit more from the use of the Oxymizer.</p>