title: Comparison of upper lip bite test and ratio of height to thyromental distance with other airway assessment tests for predicting difficult endotracheal intubation.
abstract: BACKGROUND
  Various anatomical measurements and noninvasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Upper lip bite test (ULBT) and ratio of height to thyromental distance (RHTMD) are claimed to have high predictability. Hence, we have conducted this study to compare the predictive value of ULBT and RHTMD with the following parameters: Mallampati grading, inter-incisor gap, thyromental distance, sternomental distance, head and neck movements, and horizontal length of mandible for predicting difficult intubation.
  
  
  METHODS
  In this single blinded, prospective, observational study involving 170 adult patients of either sex belonging to American Society of Anesthesiologists physical Status I-III scheduled to undergo general anesthesia were recruited. All patients were subjected to the preoperative airway assessment and, the above parameters were recorded correlated with Cormack and Lehane grade and analyzed. The number of intubation attempts and use of intubation aids were also noted.
  
  
  RESULTS
  ULBT and RHTMD had highest sensitivity (96.64%, 90.72%), specificity (82.35%, 80.39%), positive predictive value (92.74%, 91.53%), and negative predictive value (91.3%, 78.8%), respectively, compared to other parameters. While odds ratio and likelihood ratio >1 for all the tests.
  
  
  CONCLUSIONS
  ULBT can be used as a simple bedside screening test for prediction of difficult intubation, but it should be combined with other airway assessment tests for better airway predictability. RHTMD can also be used as an acceptable alternative.
authors.affiliation: Department of Anesthesiology, P. D. U. Medical College, Rajkot, Gujarat, India.
authors.forename: Jigisha Prahladrai
authors.initials: JP
authors.lastname: Badheka
authors.affiliation: Department of Anesthesiology, P. D. U. Medical College, Rajkot, Gujarat, India.
authors.forename: Pratik M
authors.initials: PM
authors.lastname: Doshi
authors.affiliation: Department of Anesthesiology, P. D. U. Medical College, Rajkot, Gujarat, India.
authors.forename: Ashutosh M
authors.initials: AM
authors.lastname: Vyas
authors.affiliation: Department of Anesthesiology, P. D. U. Medical College, Rajkot, Gujarat, India.
authors.forename: Nirav Jentilal
authors.initials: NJ
authors.lastname: Kacha
authors.affiliation: Department of Anesthesiology, P. D. U. Medical College, Rajkot, Gujarat, India.
authors.forename: Vandana S
authors.initials: VS
authors.lastname: Parmar
keywords: Airway assessment tests; difficult laryngoscopy; ratio of height to thyromental distance; upper lip bite tests