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

Background: The Oxymizer® is a special nasal cannula that provides a higher luminal diameter in combination with an incorporated oxygen (O2) reservoir. It is assumed that a higher O2 concentration can be delivered breath by breath in order to increase oxygenation. Objective: We aimed to investigate the effects of the Oxymizer on endurance time in comparison to a conventional nasal cannula (CNC). Methods: Forty-three patients with severe chronic obstructive pulmonary disease (COPD, age 60 ± 9 years, FEV1 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). Results: 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, O2 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 O2 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 O2 (≥4 liters/min). Conclusion: We show that O2 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 O2 (≥4 liters/min), in particular, may benefit more from the use of the Oxymizer.