title: The effectiveness of apneic oxygenation during tracheal intubation in various clinical settings: a narrative review.
abstract: OBJECTIVE
  During the process of tracheal intubation, patients are apneic or hypoventilating and are at risk of becoming hypoxemic. This risk is especially high in patients with acute or chronic respiratory failure and accompanying compromised respiratory reserve. To address this concern, apneic oxygenation can be administered during tracheal intubation to aid in maintaining arterial oxygen saturation. The objective of this narrative review is to examine the utilization of apneic oxygenation within the operating room, intensive care unit (ICU), emergency department, and pre-hospital settings and to determine its efficacy compared with controls.
  
  
  METHODS
  For this narrative review, we obtained pertinent articles using MEDLINE®(1946 to April 2016), EMBASE™ (1974 to April 2016), Google Scholar, and manual searches. Apneic oxygenation was administered using various techniques, including the use of nasal prongs, nasopharyngeal or endotracheal catheters, or laryngoscopes.
  
  
  RESULTS
  First, all 12 operating room studies showed that apneic oxygenation significantly prolonged the duration to, and incidence of, desaturation. Second, two of the five ICU studies showed a significantly smaller decline in oxygen saturation with apneic oxygenation, with three studies showing no statistically significant difference vs controls. Lastly, two emergency department or pre-hospital studies showed that the use of apneic oxygenation resulted in a significantly lower incidence of desaturation and smaller declines in oxygen saturation.
  
  
  CONCLUSIONS
  Sixteen of the 19 studies showed that apneic oxygenation prolongs safe apneic time and reduces the incidence of arterial oxygen desaturation. Overall, studies in this review show that apneic oxygenation prolongs the time to oxygen desaturation during tracheal intubation. Nevertheless, the majority of the studies were small in size, and they neither measured nor were adequately powered to detect adverse respiratory events or other serious rare complications. Prolonged apneic oxygenation (with its consequent hypercarbia) can have risks and should be avoided in patients with conditions such as increased intracranial pressure, metabolic acidosis, hyperkalemia, and pulmonary hypertension.
authors.affiliation: Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto, MC2-405, 399 Bathurst Street, Toronto, ON, M5T 2S8, Canada. david.wong@uhn.ca.
authors.forename: David T
authors.initials: DT
authors.lastname: Wong
authors.affiliation: Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto, MC2-405, 399 Bathurst Street, Toronto, ON, M5T 2S8, Canada.|Department of Kinesiology, McMaster University, Hamilton, ON, Canada.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Yee
authors.affiliation: Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto, MC2-405, 399 Bathurst Street, Toronto, ON, M5T 2S8, Canada.|Department of Anesthesia, National University Health System, Singapore, Singapore.
authors.forename: Siaw May
authors.initials: SM
authors.lastname: Leong
authors.affiliation: Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto, MC2-405, 399 Bathurst Street, Toronto, ON, M5T 2S8, Canada.
authors.forename: Frances
authors.initials: F
authors.lastname: Chung
mesh_terms: D001049:Apnea / Q000628:therapy*; D004636:Emergency Service, Hospital; D006801:Humans; D000860:Hypoxia / Q000517:prevention & control*; D007362:Intensive Care Units; D007442:Intubation, Intratracheal / Q000379:methods*; D009873:Operating Rooms; D010102:Oxygen Inhalation Therapy / Q000379:methods*