The Application Of Ultrasound In The Prediction Of Difficult Airway

Objective 1.To predict the difficult airway by ultrasound measuring quantification of each plane anterior neck soft tissue. Discuss the feasibility of ultrasound in the prediction of difficult airway. 2. Analysis of ultrasonic to predict difficult airway and conventional difficult airway prediction, which one is better. whether there is a difference between age and gender in predicting difficult airway. Methods Part I:patients BMI 19~25 Kg/, without snoring and apnea syndrome, no one tooth is loose, highlight, fall off, scheduled for elective surgery under general anesthesia with endotracheal intubation, were selected.Select 25 patients in each group with laryngoscope class 1, 2(group I) and 3, 4(group II). Patients horizontal position without pillow keep the spine,face and neck in the same line. The color doppler ultrasonic diagnostic instrument M- Turbo of Sonosite company production, using linear array of high frequency probe, the frequency of 6 ~ 13 MHz, measure the neck hyoid, thyrohyoid membrane, vocal cords, thyroid isthmus, and suprasternal notch five levels on measuring the thickness of the anterior soft tissue. Meanwhile, record the mouth opening, mallampati grade and thyromental distance. Recording Cormack and Lehane grade after induction of general anesthesia. Difficult laryngoscopy was defined as Cormack—Lehane grade III or IV. Whether there is statistical significance between the two groups in anterior neck soft tissue quantification, the mouth opening and thyromental distance. Part II :111 patients were under general anesthesia with endotracheal intubation. Patients horizontal position without pillow keep the spine,face and neck in the same line. Measuring thyrohyoid membrane level anterior neck soft tissue quantification. Meanwhile, recording mouth opening, mallampati grade, thyromental distance and The stretch between atlas and pillow. After anesthesia induction(fentany 6 μg/kg i.v., etomidate 0.3mg/kg i.v. and rocuronium 0.6mg/kg i.v.), endotracheal intubation with laryngoscope after 2min and recording Cormack-Lehane grade. According ROC curve, thickness of thyrohyoid membrane>2.2cm or mallampati >grade 2 or mouth opening≤3.0cm or thyromental distance≤6.5cm or the stretch between atlas and pillow≤25°can be seen as difficult airway prediction critical value. Comparing the sensitivity,specificity, accuracy, positive predictive value and negative predictive value of the two assessment methods for predicting the difficult laryngoscopy were calculated.Results Part I : There was significant difference between the two groups of the level thyrohyoid membrane. the anterior neck soft tissue quantification was(2.08±0.17cm),which was significantly thicker than that in the patients of non—difficult airway(1.79±0.12cm). The rest of the plane difference was not statistically significant(p>0.05). Part II : The sensitivity,specificity, accuracy,positive predictive value and negative predictive value of type-B ultrasonic were 75%,91%,90%,40%and 98% and there was significant difference between the two methods(p<0.05). There was no significant difference in the parameters of difficult airway which were predicted using type-B ultrasonic between the patients of different ages or gender(p>0.05).Conclusion 1.The nuchal skinfold thickness of level thyrohyoid membrane can predict difficult airway. It can accurately predict the difficult airway in the patients whose level of thyrohyoid membrane is greater than 1.95 cm.2. Measuring nuchal skinfold thickness by type-B ultrasonic to predict difficult airway is better than Conventional prediction methods about the sensitivity,specificity,accuracy,positive predictive value and negative predictive value.