The feasibility of CT rebuilding three-dimensional images of upper airway to predict difficult airway

PURPOSE:To evaluate the feasibility rebuilding three-dimensional images of the upper airway under simulating endotracheal intubation posture to predict difficult airway.METHODS:35 patients who underwent plastic and reconstructive surgery or oral and maxillofacial surgery were scanned with CT under simulating endotracheal intubation posture,and evaluated with Willson score system preoperatively.The patients whose glottises were exposed wholly or partly with a direct laryngoscope during anesthesia were accepted as normal airway,and the others were ranked as difficult airway.The midline sagittal images of the upper airway were made on computer to measure their oral areas(OA),pharyngeal areas(PA)and upper airway areas(UA).The data were processed statistically to get 95% confidence interval of the normal airway,and the lowest limit of the 95% confidence interval acted as criteria to predict difficult airway.The predictive sensitivities,positive predictive rates and false positive rates of OA,PA and UA were calculated and compared with those of Willson score system.Statistical analysis was performed using SPSS 11.5 software package for Student's t test.RESULTS:The positive predictive rate of OA and UA(72.73%,100%)were significantly higher than Willson score system(63.64%),while the positive predictive rate of PA(63.64%)was equal to Willson score system's;the predictive sensitivities of PA and UA(63.64%,57.89%)were significantly higher than Willson score system(50%),but the predictive sensitivity of OA(40%)was significantly lower than Willson score system;the false positive rate of PA(16.67%)was significantly lower than Willson score system(29.17%),but the false positive rates of OA and UA(50%,33.33%)were significantly higher than Willson score systems.CONCLUSIONS:The three-dimensionally rebuilding upper airway image was one of the suitable methods to predict difficult airway,and the lowest value of the 95% confidence interval for OA,PA and UA were significative to predict difficult airway as quantitative index.