Changes in three-dimensional computer tomography images of upper airway in patients with difficult tracheal intubation

Abstract

Objective To evaluate the changes in three-dimensional computer tomography (3DCT) images of upper airway in patients with difficult tracheal intubation and provide theoretical evidence for predicting the difficult tracheal intubation. Methods Seventeen ASA Ⅰ or Ⅱ male patients, 25-60 yr old, height 165-185 era, weight 55-110 kg, body mass index 19-33 kg/m2, scheduled for elective surgery under general anesthesia, were studied. The airway condition was evaluated with Mallampati classification and Willsan score system in all patients before the operation. The patients underwent 3DCT scanning under 2 different statuses: with or without tongue protruding while opening his mouth maximally. The volume of the oropharyngeal cavity (Va1, Va2) andtongue body (Vt1, Vt2), and area of the oropharyngeal cavity (Aa1, Aa2) and tongue body (At1, At2) in the coronal position were measured before and during tongue protruding. The midline sagittal images of the upper airway were made on computer to measure the direct laryngoscope angle and vertical distance between the mandible and hyoid (MHD). Awake blind tracheal intubation was performed in all patients. The exposure of the glottis was performed after anesthesia induction and evaluated with Cormack-Lehane classification. The patients were divided into non-difficult intubation group (group NDI, Cormack-Lehane grade Ⅰ or Ⅱ) and difficult intubation group (group DI, Cormack-Lehane grade Ⅲ or Ⅳ) according to Cormack-Lehane classification. Results There were 8 patients in group NDI, and 9 patients in group DI. There was no significant difference in the indices before tongue protruding between group DI and NDI (P>0.05). Va2, Va1 - Va1, Aa2, Aa1 - Aa2, and At1- At2 weresignificanfly smaller, MHD was significantly longer and Va1,/Vt1- Va2/Vt2was significantly larger in group DI than in group NDI (P < 0.05 or 0.01). Va2 and Aa2 were significantly smaller than Va1 and Aa1 in group DI respectively (P < 0.05). Conclusion The changes in 3DCT images of the upper airway in patients with difficult tracheal intubation are mainly presented as smaller volume and area of the oropharyngeal cavity, larger difference value of the ratio of cavity volume to tongue volume and prolonged MHD. Key words: Airway obstruction; Tomography, spiral computed