title: Pharyngeal oxygen administration increases the time to serious desaturation at intubation in acute lung injury: an experimental study.
abstract: BACKGROUND
  Endotracheal intubation in critically ill patients is associated with severe life-threatening complications in about 20%, mainly due to hypoxemia. We hypothesized that apneic oxygenation via a pharyngeal catheter during the endotracheal intubation procedure would prevent or increase the time to life-threatening hypoxemia and tested this hypothesis in an acute lung injury animal model.
  
  
  METHODS
  Eight anesthetized piglets with collapse-prone lungs induced by lung lavage were ventilated with a fraction of inspired oxygen of 1.0 and a positive end-expiratory pressure of 5 cmH2O. The shunt fraction was calculated after obtaining arterial and mixed venous blood gases. The trachea was extubated, and in randomized order each animal received either 10 L oxygen per minute or no oxygen via a pharyngeal catheter, and the time to desaturation to pulse oximeter saturation (SpO2) 60% was measured. If SpO2 was maintained at over 60%, the experiment ended when 10 minutes had elapsed.
  
  
  RESULTS
  Without pharyngeal oxygen, the animals desaturated after 103 (88-111) seconds (median and interquartile range), whereas with pharyngeal oxygen five animals had a SpO2 > 60% for the 10-minute experimental period, one animal desaturated after 7 minutes, and two animals desaturated within 90 seconds (P < 0.016, Wilcoxon signed rank test). The time to desaturation was related to shunt fraction (R2 = 0.81, P = 0.002, linear regression); the animals that desaturated within 90 seconds had shunt fractions >40%, whereas the others had shunt fractions <25%.
  
  
  CONCLUSIONS
  In this experimental acute lung injury model, pharyngeal oxygen administration markedly prolonged the time to severe desaturation during apnea, suggesting that this technique might be useful when intubating critically ill patients with acute respiratory failure.
authors.affiliation: Department of Anesthesiology and Intensive Care, Uppsala University, ANIVA ing 70 1tr, University hospital, S 75185 Uppsala, Sweden. joakim@me.com
authors.forename: Joakim
authors.initials: J
authors.lastname: Engström
authors.forename: Göran
authors.initials: G
authors.lastname: Hedenstierna
authors.forename: Anders
authors.initials: A
authors.lastname: Larsson
mesh_terms: D055371:Acute Lung Injury / Q000503:physiopathology / Q000628:therapy*; D000818:Animals; D018893:Bronchoalveolar Lavage; D002245:Carbon Dioxide / Q000097:blood; D002406:Catheterization, Peripheral; D006439:Hemodynamics; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000517:prevention & control*; D007442:Intubation, Intratracheal; D010100:Oxygen / Q000008:administration & dosage*; D010614:Pharynx; D011175:Positive-Pressure Respiration; D013548:Sweden; D013552:Swine; D016896:Treatment Outcome
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen