Physiological effects of titrated oxygen via nasal high-flow cannulae in COPD exacerbations: A randomized controlled...

Increased arterial carbon dioxide tension (PaCO₂ ) is an important complication of acute exacerbations of COPD. The effects of nasal high-flow cannulae (NHF) on PaCO₂ 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 PaCO₂ in patients admitted to hospital with a COPD exacerbation.

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 (SpO₂ ). Interventions were administered in random order with a minimum 15-min washout between interventions. The primary outcome was difference in transcutaneous carbon dioxide tension (PtCO₂ ) at 30 min adjusted for time zero.

The difference in PtCO₂ 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 SpO₂ 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).

Short-term use of NHF results in a small reduction in PtCO₂ compared with SNP in patients with acute exacerbations of COPD, but whether this is clinically significant is uncertain.