Nasal High-Flow during Exercise in Patients with COPD: A Systematic Review and Meta-Analysis.

Rationale Several studies have evaluated the effect of nasal high flow (NHF) to enhance exercise performance and tolerance in patients with COPD, however results are disparate. Objective The aim of this systematic review and meta-analysis was to assess the effect of NHF as an adjuvant to exercise training on functional exercise capacity in patients with COPD. Method An electronic search was carried out in the following databases: Pubmed, CENTRAL, PEDro, ScienceDirect, Web of Science, OpenGrey, ClinicalTrials.gov, European Respiratory Society and American Thoracic Society databases. Two authors independently selected relevant randomized trials (parallel group or cross-over design), extracted data, assessed the risk of bias and rated the quality of the evidence. Results Eleven studies were included, involving 408 participants (8 full papers and 3 conference abstracts). Most studies had a high risk of bias or other methodological limitations. The use of NHF during a single session increased functional exercise capacity (SMD 0.36 (95% CI 0.03 to 0.69) p=0.03, heterogeneity (I² 83 %)). When conference abstracts were included in the pooled analysis, the estimated effect did not change (p=0.006). The use of NHF throughout a pulmonary rehabilitation programme (parallel group RCTs) increased functional exercise capacity at 4 to 12 weeks compared with those who trained without NHF (SMD 0.34 (95% CI 0.00 to 0.68) p=0.05, heterogeneity (I² 18%)). Conclusion There is very low to low quality evidence that NHF improves functional exercise capacity. Patient responses to NHF therapy were highly variable and heterogeneous, with benefits ranging from clinically trivial to worthwhile. Registration (www.crd.york.ac.uk/prospero: CRD42021221550).