title: Physiologic Effects of High-Flow Nasal Cannula Oxygen in Critical Care Subjects.
abstract: BACKGROUND
  High-flow nasal cannula (HFNC) can deliver heated and humidified gas (up to 100% oxygen) at a maximum flow of 60 L/min via nasal prongs or cannula. The aim of this study was to assess the short-term physiologic effects of HFNC. Inspiratory muscle effort, gas exchange, dyspnea score, and comfort were evaluated.
  
  
  METHODS
  Twelve subjects admitted to the ICU for acute hypoxemic respiratory failure were prospectively included. Four study sessions were performed. The first session consisted of oxygen therapy given through a high-FIO2, non-rebreathing face mask. Recordings were then obtained during periods of HFNC and CPAP at 5 cm H2O in random order, and final measurements were performed during oxygen therapy delivered via a face mask. Each of these 4 periods lasted ∼20 min.
  
  
  RESULTS
  Esophageal pressure signals, breathing pattern, gas exchange, comfort, and dyspnea were measured. Compared with the first session, HFNC reduced inspiratory effort (pressure-time product of 156.0 [119.2-194.4] cm H2O × s/min vs 204.2 [149.6-324.7] cm H2O × s/min, P < .01) and breathing frequency (P < .01). No significant differences were observed between HFNC and CPAP for inspiratory effort and breathing frequency. Compared with the first session, PaO2/FIO2 increased significantly with HFNC (167 [157-184] mm Hg vs 156 [110-171] mm Hg, P < .01). CPAP produced significantly greater PaO2/FIO2 improvement than did HFNC. Dyspnea improved with HFNC and CPAP, but this improvement was not significant. Subject comfort was not different across the 4 sessions.
  
  
  CONCLUSIONS
  Compared with conventional oxygen therapy, HFNC improved inspiratory effort and oxygenation. In subjects with acute hypoxemic respiratory failure, HFNC is an alternative to conventional oxygen therapy. (ClinicalTrials.gov registration NCT01056952.).
authors.affiliation: Service de Réanimation Médicale, Hôpital Pellegrin-Tripode, Bordeaux, France. Centre de Recherche Cardio-thoracique, CIC 0005, Université de Bordeaux, Bordeaux, France. frederic.vargas@chu-bordeaux.fr.
authors.forename: Frederic
authors.initials: F
authors.lastname: Vargas
authors.affiliation: Service de Réanimation Médicale, Hôpital Pellegrin-Tripode, Bordeaux, France.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Saint-Leger
authors.affiliation: Service de Réanimation Médicale, Hôpital Pellegrin-Tripode, Bordeaux, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Boyer
authors.affiliation: Service de Réanimation Médicale, Hôpital Pellegrin-Tripode, Bordeaux, France.
authors.forename: Nam H
authors.initials: NH
authors.lastname: Bui
authors.affiliation: Service de Réanimation Médicale, Hôpital Pellegrin-Tripode, Bordeaux, France. Centre de Recherche Cardio-thoracique, CIC 0005, Université de Bordeaux, Bordeaux, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Hilbert
mesh_terms: D000368:Aged; D057785:Catheters; D045422:Continuous Positive Airway Pressure / Q000379:methods; D003422:Critical Care / Q000379:methods; D016638:Critical Illness / Q000628:therapy*; D004417:Dyspnea; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000628:therapy; D008297:Male; D008875:Middle Aged; D063087:Noninvasive Ventilation / Q000379:methods*; D010101:Oxygen Consumption / Q000502:physiology*; D010102:Oxygen Inhalation Therapy / Q000295:instrumentation / Q000379:methods*; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012131:Respiratory Insufficiency / Q000628:therapy*
keywords: acute hypoxemic respiratory failure; continuous positive airway pressure; high-flow nasal cannula; inspiratory effort; oxygen therapy