title: The association between obesity and difficult prehospital tracheal intubation.
abstract: BACKGROUND
  Nonphysician advanced life support (ALS) providers often perform tracheal intubation (TI) for cardiac arrest or other life-threatening indications in the prehospital setting, where airway assessment and airway management tools are limited. However, the frequency of difficult TI in obese patients in this setting is unclear. In this study we determined factors associated with TI success, and determined TI difficulty as a function of body mass index (BMI) in a system of ALS providers experienced in TI, to guide future prehospital education efforts.
  
  
  METHODS
  A retrospective review was performed of all patients ≥15 years of age who underwent prehospital TI by paramedics in the Seattle Medic One system over a 4-year period, and were transported to the regional level 1 trauma center (Harborview Medical Center). Data were abstracted from a prospectively collected prehospital airway management database and from the hospital medical records, including demographic information, number of TI attempts, TI success or failure, and body weight/height (BMI). Descriptive statistics and multivariable logistic regression were calculated, with the primary end point being difficult TI (defined as ≥4 TI attempts or the need to use an alternative airway management technique).
  
  
  RESULTS
  Of 80,501 patient contacts in whom 4114 TIs were attempted during the 4-year study period, 823 met study entry criteria (including a calculable BMI). The overall TI success rate in the study population was 98.5% (811 out of 823), with 6.8% (56 out of 823) meeting the predetermined definition for difficult TI. There was no significant association between difficult TI and patient age, gender, use of succinylcholine, or medical diagnosis (trauma vs. nontrauma). In comparison with the lean patient subgroup (BMI <30 kg/m(2)), patients with class III obesity (BMI >40 kg/m(2)) had a significant association with difficult TI (odds ratio 3.68; confidence interval [CI] 1.27-10.59), whereas those with class I/II obesity (BMI ≥30 kg/m(2) and <40 kg/m(2)) did not (odds ratio 0.98; CI 0.46 -2.07).
  
  
  CONCLUSIONS
  Among prehospital ALS providers with previously documented and published successful TI performance, increased difficulty with TI was observed in patients with extreme obesity, but not in patients with lesser degrees of obesity. Because extreme obesity is an easily identifiable patient characteristic, didactic and clinical (e.g., operating room) airway management education for such providers should emphasize airway management challenges and strategies associated with obesity, including specific equipment, patient positioning, and practice recommendations that may facilitate both TI and alternative airway management techniques in this population.
authors.affiliation: Department of Anesthesiology, University of Washington, Seattle, WA 98104, USA.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Holmberg
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Bowman
authors.forename: Keir J
authors.initials: KJ
authors.lastname: Warner
authors.forename: Monica S
authors.initials: MS
authors.lastname: Vavilala
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Bulger
authors.forename: Michael K
authors.initials: MK
authors.lastname: Copass
authors.forename: Sam R
authors.initials: SR
authors.lastname: Sharar
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D016009:Chi-Square Distribution; D002983:Clinical Competence; D004632:Emergency Medical Services; D004634:Emergency Medical Technicians; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal / Q000009:adverse effects*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000175:diagnosis; D016017:Odds Ratio; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D014861:Washington; D055815:Young Adult