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There have been many contradicting studies as to how well preoperative airway assessments predict difficult intubation. One of these measures, thyromental distance (TMD), has often been called into question. However, there have been no published studies evaluating whether anesthesia practitioners are measuring TMD accurately, especially if they use fingerbreadths as opposed to a centimeter ruler.
A convenience sample of 60 anesthesia providers were asked to participate in a brief study. The subjects were asked a series of questions, including the type of anesthesia provider they were, how often they used TMD, and their estimates in centimeters of the following fingerbreadth combinations: index finger, index and second finger, index plus second and third fingers, and index plus second, third, and fourth fingers. After their estimates were recorded, exact measurements of the fingerbreadth combinations were made at the distal interphalangeal (DIP) joints.
The differences between the means of the estimated and the actual measurements were analyzed using an independent t test. There was a statistically significant difference between estimated and actual fingerbreadth measurement for the index finger (P < .006) but not for the combinations of fingers.
Keywords: Difficult intubation, fingerbreadth measurement, preoperative airway assessment, thyromental distance.
Thyromental distance (TMD) is a measurement used to determine the horizontal distance between the thyroid prominence and the inner surface of the mandible when the head and neck are fully extended and the mouth is closed.1 This assessment is currently used to aid in the evaluation of the airway before endotracheal intubation. Preinduction measurement of thyromental distance is important, because during direct visual laryngoscopy (DVL) the tongue is displaced by the laryngoscope into the thyromental distance space.1 If the TMD is short, there is less space for tongue compression by the laryngoscope blade. In that case, visualization of the glottis and/or vocal cords can be difficult or impossible, potentially resulting in failed intubation. A TMD of less than 6 cm is generally accepted as a predictor for difficult DVL. However, few research studies agree on this measurement. In a study conducted by Tse et al,2 the minimum TMD predictor was considered to be less than 7 cm. Iohom and coworkers,3 in their study, thought a TMD of less than 6.5 cm was the predictor of choice. El-Ganzouri et...