A prospective observational study of predictors of difficult intubation in Indian patients

During routine preoperative assessment of patients one of the commonest practices is predicting difficulty of intubation. The present study was undertaken to evaluate parameters associated with difficult intubation and to test on new set of patients. At the end, to form simple predictive rule to decreased the number of false alarms.

In initial series of 483 Indian population patients we measured age, sex, weight, height, interincisor gap, mandibular length, neck movement, neck circumference, subluxation of mandible, sternocricoid distance, and identified factors associated with difficult intubation. These were applied on next 480 patients of prospective series and simple predictive rule in form of risk sum score was developed.

After analyzing initial series data we found that weight (P = 0.033), height (P = 0.034), interincisor gap (P = 0.005), subluxation (P < 0.001), neck movement (P < 0.001), and sternocricoid distance (P = 0.020) were significantly associated with difficult intubation. These six factors were applied on next set of 480 patients to found accuracy of predicting difficult intubation of weight (51.7%), height (83.8%), interincisor gap (80.2%), subluxation (77.7%), neck movement (82.7%), and sternocricoid distance (79.2). Total score greater than 2 predicted 92.8% of difficult laryngoscopies correctly as against 33.9% would be falsely labeled as difficult.

Interincisor gap and sternocricoid distance are the two most sensitive factors predicting difficult intubation in Indian patients. However, risk sum score of more than 6 may lead to better anticipation of truly difficult intubations.