A prospective observational study to predict difficult intubation using simple non-invasive tests

Sunita Sanklecha, Jyotsna Mali


Introduction: Airway assessment is the first step in successful airway management. Several anatomical and functional maneuvers can be performed to estimate the difficulty of endotracheal intubation. We aimed to elucidate the role of upper lip bite test (ULBT), hyomental/thyrosternal (HMD/TSD) distances, the mandible length (ML) and their correlation in predicting difficulty intubation in relation to laryngoscopic view as per Cormack Lehane (CL) grading.

Methods: After institutional approval informed consent obtained from160 consecutive patients aged between 20 to 60 years of ASA grading I and II scheduled for elective surgical procedures requiring tracheal intubation and meeting the inclusion criteria were enrolled in this study. Each patient was evaluated regarding ULBT, HMD, TSD, ML. Larngoscopy was assessed and findings were graded according to Cormack and Lehane's grading system.

Results: The above study states the Negative Predictive Value (NPV) and Positive Predictive Value (PPV) of ULBT were found to be 86.7% and 94.5% respectively. Specificities of ULBT, HMD, TSD and ML were found to be 98.6%, 97.8%, 96.4% and 97.8% respectively. Diagnostic accuracy of ULBT, HMD, TSD, ML were found to be 93.8% ,88.1% ,84.4% and 91.3% respectively.

Conclusion: It concludes that high specificity, NPV, PPV and Accuracy of ULBT as revealed in this study could be good rationale for its application in the prediction of difficulty or easiness in the intubation.


ULBT, HMD, TSD, ML, CL Grading, Difficult intubation

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. Peterson GN, et al. Management of the difficult airway: a closed claims analysis. Anesthesiology 2005; 103:33.

. Benumof JL. Management of the difficult adult airway. With special emphasis on awake tracheal intubation. Anesthesiology 1991; 75:1087-110. 3.

. Wilson ME, Spiegelhalter D, Robertson JA, Lesser P. Predicting difficult intubation. Br J Anaesth 1988; 61:211-6. 4.

. Turkan S, Ates Y, Cuhruk H, Tekdemir I. Should we reevaluate the variables for predicting the difficult airway in anesthesiology? Anesth Analg 2002; 94:1340-4. 5.

. Tse JC, Rimm EB, Hussain A. Predicting difficult endotracheal intubation in surgical patients scheduled for general anesthesia: A prospective blind study. Anesth Analg 1995; 81:254-8. 6.

. Shiga T, Wajima Z, Inoue T, Sakamoto A. Predicting difficult intubation in apparently normal patients: A meta-analysis of bedside screening test performance. Anesthesiology 2005; 103:429-37. 7.

. 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. 8.

. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39:1105-11. 9.

. Khan ZH, Mohammadi M, Rasouli MR, Farrokhnia F, Khan RH. The diagnostic value of the upper lip bite test combined with sternomental distance, thyromental distance, and interincisor distance for prediction of easy laryngoscopy and intubation: A prospective study. Anesth Analg 2009; 109:822-4.

. 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. 14.

. Merah NA, Foulkes-Crabbe DJ, Kushimo OT, Ajayi PA. Prediction of difficult laryngoscopy in a population of Nigerian obstetric patients. West Afr J Med 2004; 23:38-41. 15

. Jacobsen J, Jensen E, Waldau T, Poulsen TD. Preoperative evaluation of intubation conditions in patients scheduled for elective surgery. Acta Anaesthesiol Scand 1996; 40:421-4.

DOI: https://doi.org/10.7439/ijbar.v8i8.4355

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