Difficult Intubation

difficult intubation is defined as a trained Anesthetist using direct laryngoscopy take’s more than 3 attempts or more than 10 minutes to complete tracheal intubation (1, 2, 6).Difficult or failed endotracheal intubation is one of the leading causes of anesthesia-related morbidity and mortality (1, 2, 4, 6).

The unanticipated difficult airway occurs with a low but consistent incidence in anesthesia practice. Literature review from 1990 to 1996 reported as difficult direct laryngoscopy occurs in 1.5-8.5% of general anesthetics and difficult intubation occurs with a similar incidence (3, 8).

Keyvan K. et al (2000) were conducted observational study at tertiary-care level hospital to predict difficult intubation. Of the 461 patients included

et al (1995), were conducted a prospective blind study to determine whether a difficult endotracheal intubation could be predicted preoperatively by evaluation of one or more anatomic features of the head in St. Elizabeth's Medical Center of Boston. A total of 471 patients (220 men and 251 women aged 18-89 year) were enrolled in the study. Sixty-two of them were found at laryngoscopy to have airways that were difficult to intubate (laryngoscopy Grade III or IV). There were no failed intubations. Assignment to oropharyngeal Class 3, a thyromental distance 18 yr, undergoing elective surgical procedures requiring tracheal intubation by assessing preoperatively with respect to the oropharyngeal (modified Mallampati) classification, thyromental and sternomental distances. An experienced anesthetist, blinded to the preoperative airway assessment, performed laryngoscopy and graded the view according to Cormack and Lehane's classification.Twenty tracheal intubations (9%) were difficult as defined by a Cormack and Lehane Grade 3 or 4, or the requirement for a bougie in patients with Cormack and Lehane Grade 2. Used alone, the Mallampati oropharyngeal view, and thyromental and sternomental distances were associated with poor sensitivity, specificity and positive predictive values. Combining the Mallampati Class III or IV with either a thyromental distance <12.5cm decreased the sensitivity (from 40 to 25 and 20%, respectively), but maintained a negative predictive value of 93%. The specificity and positive predictive values increased from 89 and 27% respectively for Mallampati alone to 100%.The findings suggest that the Mallampati classification, in conjunction with measurement of the thyromental and sternomental distances, may be a useful routine screening test for preoperative prediction of difficult tracheal intubation