A comparison of between hyomental distance ratios, ratio of height to thyromental, modified Mallamapati classification test and upper lip bite test in predicting difficult laryngoscopy of patients undergoing general anesthesia


Departments of Anesthesia, Anesthesiology and Critical Care Research Center, Isfahan University of Medical Sciences, Isfahan, Iran


Background: Failed intubation is imperative source of anesthetic interrelated patient's mortality. The aim of this present study was to compare the ability to predict difficult visualization of the larynx from the following pre-operative airway predictive indices, in isolation and combination: Modified Mallampati test (MMT), the ratio of height to thyromental distance (RHTMD), hyomental distance ratios (HMDR), and the upper-lip-bite test (ULBT).
Materials and Methods: We collected data on 525 consecutive patients scheduled for elective surgery under general anesthesia requiring endotracheal intubation and then evaluated all four factors before surgery. A skilled anesthesiologist, not imparted of the noted pre-operative airway assessment, did the laryngoscopy and rating (as per Cormack and Lehane's classification). Sensitivity, specificity, and positive predictive value for every airway predictor in isolation and in combination were established.
Results: The most sensitive of the single tests was ULBT with a sensitivity of 90.2%. The hyomental distance extreme of head extension was the least sensitive of the single tests with a sensitivity of 56.9. The HMDR had sensitivity 86.3%. The ULBT had the highest negative predictive value: And the area under a receiver-operating characteristic curve (AUC of ROC curve) among single predictors. The AUC of ROC curve for ULBT, HMDR and RHTMD was significantly more than for MMT (P < 0.05) . No significant difference was noted in the AUC of ROC curve for ULBT, HMDR, and RHTMD (P > 0.05).
Conclusion: The HMDR is comparable with RHTMD and ULBT for prediction of difficult laryngoscopy in the general population, but was significantly more than for MMT.


1. Caplan RA, Posner KL, Ward RJ, Cheney FW. Adverse respiratory events in anesthesia: A closed claims analysis. Anesthesiology 1990;72:828-33.  Back to cited text no. 1
2. Benumof JL, Scheller MS. The importance of transtracheal jet ventilation in the management of the difficult airway. Anesthesiology 1989;71:769-78.  Back to cited text no. 2
3. Bellhouse CP, Doré C. Criteria for estimating likelihood of difficulty of endotracheal intubation with the Macintosh laryngoscope. Anaesth Intensive Care 1988;16:329-37.  Back to cited text no. 3
4. Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B, Freiberger D, et al. A clinical sign to predict difficult tracheal intubation: A prospective study. Can Anaesth Soc J 1985;32:429-34.  Back to cited text no. 4
5. Benumof JL. Difficult laryngoscopy: Obtaining the best view. Can J Anaesth 1994;41:361-5.  Back to cited text no. 5
6. Arné J, Descoins P, Fusciardi J, Ingrand P, Ferrier B, Boudigues D, et al. Preoperative assessment for difficult intubation in general and ENT surgery: Predictive value of a clinical multivariate risk index. Br J Anaesth 1998;80:140-6.  Back to cited text no. 6
7. Rocke DA, Murray WB, Rout CC, Gouws E. Relative risk analysis of factors associated with difficult intubation in obstetric anesthesia. Anesthesiology 1992;77:67-73.  Back to cited text no. 7
8. L'Hermite J, Nouvellon E, Cuvillon P, Fabbro-Peray P, Langeron O, Ripart J. The Simplified Predictive Intubation Difficulty Score: A new weighted score for difficult airway assessment. Eur J Anaesthesiol 2009;26:1003-9.  Back to cited text no. 8
9. Oates JD, Macleod AD, Oates PD, Pearsall FJ, Howie JC, Murray GD. Comparison of two methods for predicting difficult intubation. Br J Anaesth 1991;66:305-9.  Back to cited text no. 9
10. Khan ZH, Kashfi A, Ebrahimkhani E. A comparison of the upper lip bite test (a simple new technique) with modified Mallampati classification in predicting difficulty in endotracheal intubation: A prospective blinded study. Anesth Analg 2003;96:595-9.  Back to cited text no. 10
11. Braz LG, Módolo NS, do Nascimento P Jr, Bruschi BA, Castiglia YM, Ganem EM, et al. Perioperative cardiac arrest: A study of 53,718 anaesthetics over 9 yr from a Brazilian teaching hospital. Br J Anaesth 2006;96:569-75.  Back to cited text no. 11
12. Butler PJ, Dhara SS. Prediction of difficult laryngoscopy: An assessment of the thyromental distance and Mallampati predictive tests. Anaesth Intensive Care 1992;20:139-42.  Back to cited text no. 12
13. Schmitt HJ, Kirmse M, Radespiel-Troger M. Ratio of patient's height to thyromental distance improves prediction of difficult laryngoscopy. Anaesth Intensive Care 2002;30:763-5.  Back to cited text no. 13
14. Takenaka I, Iwagaki T, Aoyama K, Ishimura H, Kadoya T. Preoperative evaluation of extension capacity of the occipitoatlantoaxial complex in patients with rheumatoid arthritis: Comparison between the Bellhouse test and a new method, hyomental distance ratio. Anesthesiology 2006;104:680-5.  Back to cited text no. 14
15. American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Practice guidelines for management of the difficult airway: An updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003;98:1269-77.  Back to cited text no. 15
16. Samsoon GL, Young JR. Difficult tracheal intubation: A retrospective study. Anaesthesia 1987;42:487-90.  Back to cited text no. 16
17. Lewis M, Keramati S, Benumof JL, Berry CC. What is the best way to determine oropharyngeal classification and mandibular space length to predict difficult laryngoscopy? Anesthesiology 1994;81:69-75.  Back to cited text no. 17
18. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984;39:1105-11.  Back to cited text no. 18
19. Hanley JA, McNeil BJ. The meaning and use of the area under a receiver operating characteristic (ROC) curve. Radiology 1982;143:29-36.  Back to cited text no. 19
20. Schniederjans MJ. Mathematical partitioning of the receiver operating curve: A diagnostic tool for medical decision making. Socioecon Plann Sci 1985;19:125-35.  Back to cited text no. 20
21. Tiret L, Desmonts JM, Hatton F, Vourch G. Complications associated with anaesthesia-a prospective survey in France. Can Anaesth Soc 1986;33:336-44.  Back to cited text no. 21
22. Zuercher M, Ummenhofer W. Cardiac arrest during anesthesia. Curr Opin Crit Care 2008;14:269-74.  Back to cited text no. 22
23. Arndt M, Benad G. The risks of anesthesia in obstetric interventions. Anaesthesiol Reanim 1994;19:88-94.  Back to cited text no. 23
24. Langeron O, Masso E, Huraux C, Guggiari M, Bianchi A, Coriat P, et al. Prediction of difficult mask ventilation. Anesthesiology 2000;92:1229-36.  Back to cited text no. 24
25. Rose DK, Cohen MM. The airway: Problems and predictions in 18,500 patients. Can J Anaesth 1994;41:372-83.  Back to cited text no. 25
26. Huh J, Shin HY, Kim SH, Yoon TK, Kim DK. Diagnostic predictor of difficult laryngoscopy: The hyomental distance ratio. Anesth Analg 2009;108:544-8.  Back to cited text no. 26