title: Automated oxygen flow titration to maintain constant oxygenation.
abstract: BACKGROUND
  One century after the introduction of the oxygen flow meter into clinical practice, we have developed a device, FreeO(2), that automatically titrates the oxygen flow delivered to spontaneously breathing patients, with the aim of maintaining a stable S(pO(2)).  We evaluated this system in healthy subjects during induced hypoxemia.
  
  
  METHODS
  Hypoxemia was induced in 10 healthy subjects while breathing a gas mixture of variable F(IO(2)) (air + nitrogen). Each subject performed 3 hypoxemic challenges with the addition, in a random order,  of either: air with constant flow (1.5 L/min); oxygen with constant flow (1.5 L/min); or automatic oxygen flow titration. Subjects were blinded to the intervention. Oxygen flow, S(pO(2)), end-tidal CO(2), respiratory rate, and heart rate were recorded every second.  The primary outcome was the time with S(pO(2)) between 92% and 96%.
  
  
  RESULTS
  The S(pO(2)) target (92-96%) was achieved a median of 26.0%, 36.8%, and 66.5% (P < .001) of the time with air, constant oxygen, and automated oxygen titration,  respectively. Severe oxygen desaturations (S(pO(2)) < 88%) were respectively observed at a median of 33.7%, 12.7%, and 0.4% of the time (P < .001). Hyperoxia was present a median of 4.1%, 39.1%, and 14.5% of the time (P < .001). Tachycardia was present  with air and with constant oxygen flow, but not while using automated oxygen titration. These results were obtained with a mean and maximal oxygen flow of 1.3 L/min and 7.6 L/min with the automated titration.
  
  
  CONCLUSIONS
  In this model of induced hypoxemia, the FreeO(2) system that  automatically titrates the oxygen flow was more efficient at maintaining the S(pO(2)) target, while ensuring a statistically significant reduction in the rates of severe hypoxemia and hyperoxia, in comparison with air or constant oxygen flow. These beneficial results were  obtained with less oxygen, in comparison to a constant oxygen flow.
authors.affiliation: Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada. francois.lellouche@criucpq.ulaval.ca
authors.forename: François
authors.initials: F
authors.lastname: Lellouche
authors.forename: Erwan
authors.initials: E
authors.lastname: L'her
mesh_terms: D000328:Adult; D000465:Algorithms; D018592:Cross-Over Studies; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D010102:Oxygen Inhalation Therapy / Q000295:instrumentation*; D012143:Respiratory Physiological Phenomena; D013990:Tidal Volume / Q000502:physiology