Upper Lip Bite Test : A Novel Test of Predicting Difficulty in Intubation

Abstract

BACKGROUND:Although there are many preoperative tests to predict difficult airway, they are far from being ideal i. e. easy to perform, highly sensitive and specific, having high positive predictive value with few false positive predictions. AIMS: to elucidate the role of upper lip bite test (ULBT) with other prevailing tests, hyomental/thyrosternal distance ((HMD/ TSD), and mandible length (ML) in predicting difficulty in endotracheal intubation. MATERIAL AND METHOD: 300 patients meeting inclusion criteria, aged 21-60 yrs. having ASA I and II status, posted for elective surgery under general anesthesia with endotracheal intubation were enrolled in this study. Preoperatively anesthesiologist not involved in intubation evaluated and assessed the ULBT class and obtained measurements of HMD, TSD, ML. Laryngoscopy was assesed by anesthesiologist blinded to the measurements and was graded according to Cormack and Lahane's Grading system. ULBT of class III, HMD<3.5cms, TSD<6.5cms and ML <9cms were considered as markers of a potentially difficult intubation. STATISTICAL ANALYSIS: Data was analysed using kappa agreement and sensitivity, specificity, positive predictive value, negative predictive value with their 95% confidence interval was calculated. RESULTS: The negative predictive value (NPV) and positive predictive value (PPV) of ULBT were 100% and 92. 2% respectively. These corresponding figures for HMD, ML, and TSD were 57.14, 0, 81.82 and 87, 71, 86.39, 89.27 respectively. Specificities for ULBT, HMD, ML, TSD were 45, 10, 0, 22.5% respectively. Sensitivity for ULBT, HMD, ML, TSD was 100, 98.85, 99.23, 97.69 respectively. ULBT showed greatest agreement with laryngoscopic grading (kappa=. 59 with p-value <0.0001). An agreement between HMD, ML, TSD and laryngoscopic grading which was comparatively weaker also existed (0.14, 0.31, -0.04, respectively.) CONCLUSION: The high specificity, NPV, PPV, and accuracy of ULBT as revealed in this study could be a good rationale for its application in the prediction of difficulty or easiness in intubation. The quantitative parameters, ML and HMD, had a slight and fair agreement with kappa coefficient. Hence, either of them can be useful in combination with a qualitative parameter, ULBT, so as to get acceptable and dependable result as it enhances its potential value in being diagnostic in airway assessment.

Bedside tests for predicting difficult airways: an abridged Cochrane diagnostic test accuracy systematic review

“…). After detailed assessment, we included 133 studies (127 cohort type and six case–control) involving 844,206 participants . Of the 133 studies, there were six for the Mallampati test, 105 for the modified Mallampati test, six for Wilson risk score, 52 for thyromental distance, 18 for sternomental distance, 34 for the mouth opening test and 30 for the upper lip bite test.…”

2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway

“…Observational studies reported comparative findings for facial and jaw features and anatomical measurement for difficult versus nondifficult airway patients as well as sensitivity, specificity, positive predictive, negative predictive, and accuracy values for difficult laryngoscopy and intubation. Findings for facial and jaw features, 7–11,13,14,18,27,33,38–40,42,43,45–47,49,51–54,57,58,64,68,123–159 anatomical measurements, 7–11,13–15,18,22,23,27–30,33,35,37–40,45–47,49,51–54,57,58,60, 64,65,68,70,123–132,134–154,156,158–203 and ultrasound anatomical measurements 69,139,162,170,194,196,203–213 were shown to have very high predictive and comparative variability, with sensitivity, specificity, and significance values ranging from low to very high across all patient measures (Category B2-E evidence). No single characteristic was identified as consistently being more predictive than another, and multivariate measures intended to predict difficult airways were too few and diverse among the studies to determine a common set of predictors.…”

Evaluation of preoperative difficult airway prediction methods for adult patients without obvious airway abnormalities: a systematic review and meta-analysis

“…One hundred seventy-eight papers used prospective design, twelve used retrospective design, eighteen papers used case–control design. Sixty-nine papers used blinded experiment [ 15 , 20 , 25 , 29 – 31 , 44 , 50 , 57 , 60 , 61 , 63 , 71 , 75 , 77 , 86 , 90 , 91 , 95 , 98 , 102 , 112 , 115 , 116 , 123 – 125 , 127 – 129 , 139 , 140 , 143 , 147 , 152 , 159 – 161 , 169 , 171 – 174 , 179 – 183 , 185 , 186 , 188 – 192 , 196 , 201 , 204 , 208 , 209 , 211 , 218 , 228 – 230 , 234 ]. Twenty-four specifically selected obese populations for research [ 36 , 39 , 40 , 43 , 59 , 61 , 65 , 70 , 86 , 99 , 106 , 109 , 121 ,…”

“…Almost all studies indicated that difficult tracheal intubation assessment was performed before surgery. Only 69 articles explicitly used blinded methods [ 15 , 20 , 25 , 29 – 31 , 44 , 50 , 57 , 60 , 61 , 63 , 71 , 75 , 77 , 86 , 90 , 91 , 95 , 98 , 102 , 112 , 115 , 116 , 123 – 125 , 127 – 129 , 139 , 140 , 143 , 147 , 152 , 159 – 161 , 169 , 171 – 174 , 179 – 183 , 185 , 186 , 188 – 192 , 196 , 201 , 204 , 208 , 209 , 211 , 218 , 228 – 230 , 234 ]. When assessing the risk of bias in 227 studies using the QUADAS-2 tool, 27 studies showed problems with patient selection, 10 studies showed problems with index testing, 49 studies showed problems with reference standards, and 33 studies showed problems with procedures and timing.…”