ABSTRACT
Objective To explore the predictive capability of different methods for difficult la-ryngoscopy and analyze its optimal cutoff value.Methods Three hundred consecutive patients (aged 18-65 years,weighing 42-88 kg,ASA physical status Ⅰ or Ⅱ)scheduled to undergo general anesthe-sia and surgery were invited to participate.Difficult airway assessments were performed by thyromen-tal height (TMH),thyromental distance (TMD),sternomental distance (SMD),modified Mallam-pati test (MMT)and ratio of height and TMD (RHTMD)before anesthetic induction.Cormack-Le-hane (C-L)grade of laryngoscopy view was assessed after induction.Sensitivity,specificity,positive predictive value (PPV),negative predictive value (NPV)and accuracy of these tests were calculated. Receiver operator characteristic (ROC)curve of TMH was performed to determine the optimal cutoff value of TMH.Results There were 22 patients diagnosed as difficult airway.Sensitivity,specificity, PPV,NPV and accuracy of TMH were higher than those of TMD,SMD and MMT tests.Sensitivity of RHTMD was lower than that of TMH test,and specificity,PPV,NPV and accuracy of RHTMD were similar to that of TMH.The optimal cutoff value of TMH was 4.9 cm through ROC curve. Conclusion The optimal cutoff value of TMH detecting difficult laryngoscopy was 4.9 cm.Similar to RHTMD,TMH appears to be more effective for prediction of difficult laryngoscopy than TMD, SMD and MMT.
ABSTRACT
Objective To analyze retrospectively the correlation between the difficult airway and thyromental height by three-dimensional reconstruction among the Chinese. Methods Eithty patients who had been scanned by helical CT in the head and neck were allocated into two groups according to Cormack-Lehane grading:paients with Ⅰ-Ⅱ grade were allocated into group 1, and paients with Ⅲgrade were allocated into group 2. Reconstructed images were obtained by AW4.4 workstation and the following parameters were recorded and analyzed:the length from the oral to the under jaw(a), the length from the under jaw to the skin of the neck (b), the vertical distance from the under jaw to the neck was equal to thyromental height(c), the vertical distance from the oral to the cervical vertebra(d), the angle with the under jaw as the vertices and with two lines (a and b) for edge (angle ofα). Results The c value in two groups had no significant difference:(3.97 ± 0.82) cm vs. (3.64 ± 0.62) cm, P>0.05. The d value in group 2 was significantly higher than that in group 1:(8.69 ± 0.48) cm vs. (8.25 ± 0.80) cm, P<0.05. The c/d value and c/a value in group 2 were significantly lower than those in group 1: 0.42 ± 0.07 vs. 0.48 ± 0.12, 0.80 ± 0.18 vs. 0.95 ± 0.25, P<0.05. Conclusions Thyromental height by three-dimensional reconstruction has no significant differences in evaluating the difficult airway among the Chinese. The ratio of the vertical distance from the under jaw to the neck and the vertical distance from the oral to the cervical vertebra, and the ratio of the vertical distance from the under jaw to the neck and the length from the oral to the under jaw shows negative correlation with difficult airway.