Background Prehospital tracheal intubation (TI) is associated with morbidity and mortality, particularly in cases of difficult intubation. The goal of the present study was to describe factors associated with TI related complications in the prehospital setting.

Methods This was a prospective cohort study including all patients intubated on scene in a prehospital emergency medical service over a 4 year period. TI related complications included oxygen desaturation, aspiration, vomiting, bronchospasm and/or laryngospasm, and mechanical complications (mainstem intubation, oesophageal intubation and airway lesion— that is, dental or laryngeal trauma caused by the laryngoscope). Difficult intubation was defined as >2 failed laryngoscopic attempts, or the need for any alternative TI method. A multivariate logistic regression was used to identify the risk factors for TI related complications.

Results 1251 patients were included; 208 complications occurred in 165 patients (13.1%). Among the 208 complications, the most frequent were oesophageal intubation (n=69, 29.7%), desaturation (n=58, 25.0%) and mainstem intubation (n=37, 15.9%). In multivariate analysis, difficult intubation (OR=6.13, 3.93 to 9.54), Cormack and Lehane grades 3 and 4 (OR=2.23, 1.26 to 3.96 for Cormack and Lehane grade 3 and OR=2.61, 1.28 to 5.33 for Cormack and Lehane grade 4 compared with Cormack and Lehane grade 1) and a body mass index >30 kg/m² (OR=2.22, 1.38 to 3.56) were significantly associated with TI related complications.

Conclusions Despite specific guidelines, TI related complications are more frequent in the prehospital setting when intubation is deemed difficult, the Cormack and Lehane grade is greater than grade 1 and the patient is overweight. In such situations, particular attention is needed to avoid complications.