Prediction of difficult laryngoscopy in a population of Nigerian obstetric patients

Difficulty in the maintenance of the airway during obstetric anaesthesia is a major contributory factor in anaesthetic related morbidity and mortality. There is an eightfold increase in the incidence of failed intubation in obstetrics. This is attributable to the physiological changes in pregnancy. Eighty consecutive obstetric patients, over a one year period who required general anaesthesia for caesarian section were evaluated using five bedside tests viz: Mallampati test, Thyrometal distance, Sterno-mental distance, Horizontal length of the Mandible and Inter-incisor gap. Eight patients had difficult laryngoscopy (10%). Mallampati test had a sensitivity, specificity and positive predictive value of 87.1%, 99.6% and 70% respectively. The values obtained for the Thyro-mental distance were 62.5%, 93.1% and 50% respectively. The other tests were not able to predict intubation difficulty significantly. When all tests were combined, sensitivity, specificity and positive predictive were values 100%, 36.1% and 14.8%. The combination of Mallampati and Thyro-mental distance had values of 100%, 93.1% and 61.5%--sensitivity, specificity and positive predictive value. Mallampati can be used as the sole predictor of difficult intubation in Nigerian obstetric patients.