Benefits of a reservoir nasal cannula (oxymizer) versus a conventional nasal cannula during exercise in hypoxemic COPD patients

Background: The Oxymizer ® device is a special oxygen nasal cannula that provides a higher luminal diameter in combination with an incorporated oxygen reservoir. Thus it is assumed that a higher oxygen content can be delivered in order to increase oxygenation. Methods: Aim of this prospective cross-over study was to investigate the effects of the Oxymizer ® in comparison to a conventional nasal cannula (CNC). N=43 patients with severe COPD (age: 60±9y, FEV 1 : 37±16% pred.) and indication for long-term oxygen therapy were recruited during pulmonary rehabilitation. After an initial incremental cycle test patients performed 4 constant cycling work rate tests (CWRT) at 70% of their peak work rate (twice with Oxymizer ® and twice with CNC in random order). Results: Endurance time was significantly higher when patients cycled using Oxymizer ® in comparison to CNC (858±754 sec. vs 766±652 sec.; p<0.01). Beside of a longer cycling duration, PaO 2 values at the end of CWRT were also significantly higher with Oxymizer ® (65±11 mmHg versus 62±10 mmHg; p<0.001). However, in a subgroup analysis we found that patients with an oxygen supplementation of ≥4 liters/min obtained an markedly higher increase in exercise capacity by using the Oxymizer ® than patients with lower oxygen flow rates (increase in endurance time 161±225 sec. versus 20±123 sec.; p<0.05). Conclusion: This study showed that oxygen delivery via Oxymizer ® is superior to CNC with regards to endurance capacity and a better oxygenation during exercise in patients with severe COPD. It seems that especially patients with high oxygen flow rates of ≥4 liters/min benefit most from the use of an Oxymizer ® .