Nasal high-flow in acute hypercapnic exacerbation of COPD

Jens Bräunlich, Hubert Wirtz Department of Respiratory Medicine, University of Leipzig, Leipzig, Germany Since the late 1980s non-invasive ventilatory support (NIV) has become a standard treatment in acute exacerbation of COPD (AECOPD) with hypercapnia.1 Although NIV has been shown to be extremely useful in this situation, but up to 30% of hypercapnic AECOPD patients do not tolerate NIV for several reasons.2 Nasal high-flow (NHF) provides a warmed and humidified airflow up to 60 Liter/min through a specialized nasal cannula. Oxygen admixture is readily available and should be dosed to a desired saturation.3 NHF combines a wash-out effect with a decrease in CO2 rebreathing, support of inspiratory flow, a small increase in airway pressure, a lowering of ambient air admixture during inspiration and possibly a beneficial effect of warmed and saturated air in the airways. Together, these effects lead to a stabilization of oxygen delivery at higher respiratory rates, a decrease in the work of breathing noticeable by a lower respiratory rate and reduced hypercapnia.4–6 Several studies evaluated the effectiveness of NHF therapy in a variety of clinical situations with effects comparable to NIV.3,7 Most of these investigations excluded patients with hypercapnia. It is therefore, impossible to draw meaningful conclusions on the effectiveness of NHF in AECOPD. Several smaller series have observed a significant decrease in partial arterialized carbon dioxide pressure of CO2 (paCO2) in chronic hypercapnic COPD patients.4,6 There are no data available about other endpoints or in a cohort of solely hypercapnic AECOPD patients