Anatomical Features of the Neck as Predictive Markers of Difficult Laryngoscopy in Men and Women: A Prospective Study

Background Difficult or failed airway management is the major factor in anesthesia related morbidity and death. Studies of anatomic variables and their implications for difficult airway management have shown that there is low sensitivity, specificity and positive predictive value for any single test, however, correlation is better with a combination of tests. Aim Aim is to evaluate four anatomic features of the neck, namely thyromental distance, sternomental distance, the ratio of height to thyromental distance and neck circumference which can be measured pre-operatively with minimal patient co-operation and to assess their diagnostic value in predicting difficult laryngoscopy Design Prospective observational study Setting Department of Anaesthesiology, Government Medical college, Thiruvananthapuram, Kerala, India, a tertiary care teaching hospital. Patients This study was conducted in 607 adult patients, scheduled for elective surgical procedures under general anesthesia with endotracheal intubation. Main outcome measures The outcome variable studied was difficult laryngoscopy, defined as Cormack-Lehane Grade 3 and 4 of laryngoscopic view Results The laryngoscopy was assessed as difficult in 109 (18.0%) of the studied patients. The diagnostic value of thyromental distance was found unsatisfactory in the present study. Analysis of data in the present study indicates that sternomental distance is of limited predictive accuracy when used alone. Ratio of height to thyromental distance had relatively good negative predictive value (87.1%) This study found the neck circumference to be the most sensitive and specific test in predicting difficult laryngoscopy among the tests studied. NC had highest sensitivity (72.5%) and specificity (74.1%) with a positive predictive value of 38.0% and negative predictive value of 92.5%. Analysis of data from the present study showed that NC can be used as sole predictor of difficult laryngoscopy in men and women.