Abstract
BackgroundSeveral methods have been used to predict difficult tracheal intubation. Among recently suggested methods, the upper lip bite test (ULBT) could serve as a good predictor. Soft tissue and skeletal hard tissue profiles are affected by many factors including ethnicity. We aimed to assess the clinical utility of the ULBT in Koreans while considering ethnic differences.MethodsThree-hundred-forty-four Korean patients undergoing general anesthesia with orotracheal intubation were included. Preoperatively, we recorded the patient’s Modified Mallampati (MMT) classification, ULBT ratings, and the Cormack–Lehane grade.ResultsThe area under the receiver operating characteristic (ROC) curve (AUC) was lower for the ULBT than the MMT (95% confidence interval: 0.0697–0.191, p < 0.0001). The ULBT showed high accuracy (73.83%) and specificity (98.04%). On the other hand, the ULBT showed significantly lower sensitivity (4.49%). Only nine of 344 Korean patients could not bite their upper lip; among them, only three presented a difficult laryngoscopic view.ConclusionsOne factor related to the low sensitivity is the low incidence of a grade III ULBT in Koreans. In Asians, the scarcity of a grade III ULBT is explainable as a result of anteriorly displaced temporomandibular joints and redundant lip soft tissues. Despite its high specificity, the low sensitivity and AUC of the ULBT mean that the test results should be interpreted cautiously in Koreans. Ethnic differences should be considered when evaluating parameters related to soft tissues such as the ULBT.Trial registrationClinicalTrials.gov Identifier: NCT01908218, Date of registration JUL 2013.
Highlights
Several methods have been used to predict difficult tracheal intubation
* Correspondence: iatria@hanmail.net Department of Anesthesiology and Pain Medicine, CHA Bundang Medical Center, CHA University, 59 Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13496, South Korea of the upper lip with the lower incisors [1]. This simple bedside test was shown to have a good predictive value, specificity, and accuracy without the need for a light or sitting position [1, 2]. This method was based on cephalometric measurements, which differed in skeletal hard tissue and soft tissue profiles of Asian and Caucasian populations [3,4,5,6,7,8,9,10]
After the loss of a response to a train- of -four or single- twitch ulnar nerve stimulation, laryngoscopy was performed by three skilled anesthesiologists using a Macintosh laryngoscope with a size 3 or 4 blades
Summary
Several methods have been used to predict difficult tracheal intubation. The upper lip bite test (ULBT) could serve as a good predictor. Khan et al suggested the upper lip bite test (ULBT) to, evaluates the ability of a patient to cover the mucosa. This method was based on cephalometric measurements, which differed in skeletal hard tissue and soft tissue profiles of Asian and Caucasian populations [3,4,5,6,7,8,9,10]. The ULBT evaluates mandibular movement, which reflects differences in skeletal hard tissue and the conjointed movements of the ligaments, connective tissues, and soft tissues. We suppose these discrepancies might be derived from cephalometric differences in Asian
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