Radiographic Predictors of Difficult Fiberscopic Intubation During General Anesthesia in Patients With a Cervical Collar to Simulate a Difficult Airway

Background: Predictors of difficult fiberscopic intubation have not been fully elucidated. This study focused on identifying radiographic predictors of difficult fiberscopic intubation during general anesthesia in patients with a cervical collar.

Methods: This retrospective study included unconscious patients who underwent orotracheal intubation using a flexible fiberscope while wearing a cervical collar to simulate a difficult airway. Easy fiberscopic intubation was defined as successful fiberscopic intubation within 120 seconds on the first attempt without desaturation below 90%. The patients were divided into easy (n=133) and difficult (n=24) fiberscopic intubation groups. Demographic, mask ventilation-related, upper airway-related, and radiographic variables measured on sagittal images of preoperative cervical x-ray and magnetic resonance imaging were analyzed.

Results: The difficult fiberscopic intubation group had a smaller oral cavity area (2.1 [1.2-2.5] vs. 2.9 [2.1-3.7] cm2, P<0.001), higher tongue area divided by oral cavity area (9.3 [6.5-13.3] vs. 6.4 [4.6-8.3], P<0.001), smaller epiglottis angle (33±10° vs. 37±8°, P=0.02), and longer skin-glottis distance (1.3 [1.1-1.6] vs. 1.1 [1.0-1.3] cm, P=0.004). Tongue area/oral cavity area (odds ratio per 1 [95% CI]: 1.24 [1.09-1.40]) and skin-glottis distance (odds ratio per 1 cm [95% CI]: 13.0 [2.69-62.4]) were independently associated with the difficulty in fiberscopic intubation.

Conclusions: High tongue area/oral cavity area and long skin-glottis distance were predictive of difficult fiberscopic intubation during general anesthesia in patients with a cervical collar.