Utility of difficult laryngoscopy screening methods for out-of-hospital intubation

Abstract

Study objectives: Scoring systems for the assessment of difficult laryngoscopy, such as Mallampati score, measurement of oral opening, thyromental distance, and neck mobility, may have limited utility in the out-of-hospital setting where many patients undergoing intubation are not able to cooperate because of altered mental status or cervical spine immobilization. We determine the frequency of out-of-hospital intubations occurring in patients able to comply with common difficult laryngoscopy scoring systems. Methods: We conducted a retrospective review of a consecutive series of intubations at a university-based air medical transport program from January 1998 to September 2003. The records of all patients requiring oral intubation were reviewed. Exclusion criteria were age younger than 18 years and incomplete medical record data. Mallampati score and oral opening were judged to be unobtainable in patients who could not follow commands (Glasgow Coma Scale [GCS] motor score <6). Neck mobility and thyromental distance were deemed unobtainable in patients with cervical spine immobilization. Results: Four hundred twenty-three intubations were performed. Exclusion of 73 patients younger than 18 years and 19 patients with incomplete records yielded 331 intubations. Overall intubation success rate was 97%, and rapid sequence intubation was used in 77% of patients. Two hundred eighty (85%) patients had GCS motor score less than 6, and 235 (71%) patients were immobilized. Two hundred nine (63%) patients had GCS motor score less than 6 and were immobilized. Only 25 (8%) patients could follow commands and were not immobilized. Interrater reliability in recording of GCS scores and presence of spine immobilization was identical in 30 of 30 (100%) of randomly selected records. Conclusion: Only 8% of patients intubated in this out-of-hospital population could follow commands and were not immobilized, which severely limits the applicability of Mallampati scores, measurement of oral opening, thyromental distance, and neck mobility to predict difficult intubation in the out-of-hospital setting. Study limitations include retrospective data collection.