title: Nasal high flow oxygen therapy in patients with COPD reduces respiratory rate and tissue carbon dioxide while increasing tidal and end-expiratory lung volumes: a randomised crossover trial.
abstract: Patients with COPD using long-term oxygen therapy (LTOT) over 15 h per day have improved outcomes. As inhalation of dry cold gas is detrimental to mucociliary clearance, humidified nasal high flow (NHF) oxygen may reduce frequency of exacerbations, while improving lung function and quality of life in this cohort. In this randomised crossover study, we assessed short-term physiological responses to NHF therapy in 30 males chronically treated with LTOT. LTOT (2-4 L/min) through nasal cannula was compared with NHF at 30 L/min from an AIRVO through an Optiflow nasal interface with entrained supplemental oxygen. Comparing NHF with LTOT: transcutaneous carbon dioxide (TcCO2) (43.3 vs 46.7 mm Hg, p<0.001), transcutaneous oxygen (TcO2) (97.1 vs 101.2 mm Hg, p=0.01), I:E ratio (0.75 vs 0.86, p=0.02) and respiratory rate (RR) (15.4 vs 19.2 bpm, p<0.001) were lower; and tidal volume (Vt) (0.50 vs 0.40, p=0.003) and end-expiratory lung volume (EELV) (174% vs 113%, p<0.001) were higher. EELV is expressed as relative change from baseline (%Δ). Subjective dyspnoea and interface comfort favoured LTOT. NHF decreased TcCO2, I:E ratio and RR, with a concurrent increase in EELV and Vt compared with LTOT. This demonstrates a potential mechanistic rationale behind the improved outcomes observed in long-term treatment with NHF in oxygen-dependent patients.
  
  
  
  ACTRN12613000028707.
authors.affiliation: Critical Care Research Group, The Prince Charles Hospital and University of Queensland, Brisbane, Australia.
authors.forename: John F
authors.initials: JF
authors.lastname: Fraser
authors.affiliation: Critical Care Research Group, The Prince Charles Hospital and University of Queensland, Brisbane, Australia.
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Spooner
authors.affiliation: Critical Care Research Group, The Prince Charles Hospital and University of Queensland, Brisbane, Australia Biomedical Engineering and Medical Physics, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Australia.
authors.forename: Kimble R
authors.initials: KR
authors.lastname: Dunster
authors.affiliation: Critical Care Research Group, The Prince Charles Hospital and University of Queensland, Brisbane, Australia Intensive Care Unit, Nambour General Hospital, Nambour, Australia.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Anstey
authors.affiliation: Critical Care Research Group, The Prince Charles Hospital and University of Queensland, Brisbane, Australia.
authors.forename: Amanda
authors.initials: A
authors.lastname: Corley
mesh_terms: D002245:Carbon Dioxide / Q000032:analysis; D015331:Cohort Studies; D018592:Cross-Over Studies; D006801:Humans; D008134:Long-Term Care; D008297:Male; D010092:Oximetry; D010102:Oxygen Inhalation Therapy / Q000379:methods; D010366:Peak Expiratory Flow Rate; D011175:Positive-Pressure Respiration / Q000379:methods; D029424:Pulmonary Disease, Chronic Obstructive / Q000628:therapy*; D011788:Quality of Life; D056152:Respiratory Rate; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide
keywords: COPD Exacerbations; Long Term Oxygen Therapy (LTOT); Non invasive ventilation