Physiological effects of titrated oxygen via nasal high‐flow cannulae in COPD exacerbations: A randomized controlled cross‐over trial

Background and objective Increased arterial carbon dioxide tension ( PaCO 2 ) is an important complication of acute exacerbations of COPD . The effects of nasal high‐flow cannulae ( NHF ) on PaCO 2 in patients with COPD exacerbations, and whether this therapy should be used in this clinical situation, are less certain. We aimed to investigate the effect of NHF on PaCO 2 in patients admitted to hospital with a COPD exacerbation. Methods We performed a single‐centre randomized controlled cross‐over trial in 24 hospital inpatients with acute exacerbations of COPD receiving oxygen via standard nasal prongs ( SNPs ). Patients received both supplemental oxygen via NHF (35 L/min) and SNP for 30 min each, with oxygen titrated to maintain the patient's baseline oxygen saturation, measured by pulse oximetry ( SpO 2 ). Interventions were administered in random order with a minimum 15‐min washout between interventions. The primary outcome was difference in transcutaneous carbon dioxide tension ( PtCO 2 ) at 30 min adjusted for time zero. Results The difference in PtCO 2 adjusted for time zero was lower after 30 min for NHF compared with SNP (−1.4 mm Hg (95% CI : −2.2 to −0.6), P  = 0.001). There was no difference in SpO 2 at 30 min (−0.02% (95% CI : −0.8 to 0.7), P  = 0.96). The reduction in respiratory rate for NHF at 30 min was not statistically significant (−2.0 breaths/min (95% CI : −4.5 to 0.4), P  = 0.099). Conclusion Short‐term use of NHF results in a small reduction in PtCO 2 compared with SNP in patients with acute exacerbations of COPD , but whether this is clinically significant is uncertain.