title: Hypoxemia during aeromedical evacuation of the walking wounded.
abstract: BACKGROUND
  Hypobaric hypoxemia is a well-known risk of aeromedical evacuation (AE). Validating patients as safe to fly includes assessment of oxygenation status as well as oxygen-carrying capability (hemoglobin). The incidence and severity of hypoxemia during AE of noncritically injured casualties have not been studied.
  
  
  METHODS
  Subjects deemed safe to fly by the validating flight surgeon were monitored with pulse oximetry from the flight line until arrival at definitive care. All subjects were US military personnel or contractors following traumatic injuries. Noninvasive oxygen saturation (SpO2), pulse rate, and noninvasive hemoglobin were measured every 5 seconds and recorded to electronic memory. Patient demographics and physiologic data were collected by chart abstraction from the Air Force Form 3899, patient movement record. The incidence and duration of hypoxemic events (SpO2 < 90%) and critical hypoxemic events were determined (SpO2 < 85%).
  
  
  RESULTS
  Sixty-one casualties were evaluated during AE from Bagram Air Base to Landstuhl Regional Medical Center. The mean (SD) age was 26.2 (6) years, Injury Severity Score (ISS) was 8 (11), and mean SpO2 before AE was 96% (2%). The mean (SD) transport time was 9.3 (1.3) hours. Patients were monitored before AE for a brief period, yielding a total recording time of 10.28 hours. The mean (SD) hemoglobin at the time of enrollment was 13.2 (3.5) g/dL (9.4-18.0 g/dL). Hypoxemia (SpO2 < 90%) was seen in 55 (90%) of 61 subjects. The mean duration of SpO2 less than 90% was 44 minutes. The mean (SD) change in SpO2 from baseline to mean in-flight SpO2 was 4% (1.2%). Thirty-four patients (56%) exhibited an SpO2 less than 85% for 11.7 (15) minutes.
  
  
  CONCLUSIONS
  Hypoxemia is a common event during AE of casualties. In patients with infection and concussion or mild traumatic brain injury, this could have long-term consequences.
  
  
  METHODS
  Epidemiologic/prognostic study, level V.
authors.affiliation: From the Division of Trauma and Critical Care (J.J.), University of Cincinnati (D.R., T.B., R.B.); and Center for Sustainment of Trauma and Readiness Skills-Cincinnati (T.G., D.C., T.B., J.E.), Cincinnati, Ohio.
authors.forename: Jay
authors.initials: J
authors.lastname: Johannigman
authors.forename: Travis
authors.initials: T
authors.lastname: Gerlach
authors.forename: Daniel
authors.initials: D
authors.lastname: Cox
authors.forename: Jon
authors.initials: J
authors.lastname: Juhasz
authors.forename: Tyler
authors.initials: T
authors.lastname: Britton
authors.forename: Joel
authors.initials: J
authors.lastname: Elterman
authors.forename: Dario
authors.initials: D
authors.lastname: Rodriquez
authors.forename: Thomas
authors.initials: T
authors.lastname: Blakeman
authors.forename: Richard
authors.initials: R
authors.lastname: Branson
mesh_terms: D000328:Adult; D017732:Air Ambulances; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000209:etiology*; D015601:Injury Severity Score; D008297:Male; D008889:Military Personnel; D010092:Oximetry; D014481:United States