Reduction of PaCO2 by high-flow nasal cannula in acute hypercapnic respiratory failure patients receiving conventional oxygen therapy.Lee HW1, Choi SM1, Lee J1, Park YS1, Lee CH1, Yoo CG1, Kim YW1, Han SK1, Lee SM1.Author information1Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.AbstractBACKGROUND:It has been suggested that a high-flow nasal cannula (HFNC) could help to remove carbon dioxide (CO2) from anatomical dead spaces, but evidence to support that is lacking. The objective of this study was to elucidate whether use of an HFNC could reduce the arterial partial pressure of CO2 (PaCO2) in patients with acute hypercapnic respiratory failure who are receiving conventional oxygen (O2) therapy.METHODS:A propensity score-matched observational study was conducted to evaluate patients treated with an HFNC for acute hypercapnic respiratory failure from 2015 to 2016. The hypercapnia group was defined as patients with a PaCO2 >50 mm Hg and arterial pH