Clinical and ultrasonographic assessment of airway indices among non-pregnant, normotensive pregnant and pre-eclamptic patients: a prospective observational study

Background: Prediction of a difficult airway is of paramount importance for an anaesthesiologist. Various anatomical and physiological factors contribute to a difficult airway in pregnant females, especially those with pre-eclampsia. The aim of the study was to assess airway indices using both routinely used clinical methods and ultrasound.Methods: Fifty-five non-pregnant females, 55 normotensive pregnant females and 55 females with pre-eclampsia were included in this prospective study. Clinical airway assessment was the modified Mallampati score, thyro-mental distance, hyomental distance, hyomental distance ratio, chest circumference, neck circumference and chest-to-neck circumference ratio. Sonographic assessment included tongue width, tongue volume, anterior neck soft tissue thickness at the level of hyoid, epiglottis and vocal cords, subglottic diameter, ratio of pre-epiglottic space to anterior, posterior and midpoint of anterior and posterior vocal folds.Results: Several significant differences were observed between pregnant and non-pregnant females, with addi-tional changes in pre-eclamptic females. These included clinical parameters such as the modified Mallampati score and sonographic measurements of tongue width, tongue volume, subglottic diameter, anterior neck soft tis-sue thickness at the level of hyoid, epiglottis and vocal cords, and the ratio of pre-epiglottic space to anterior, pos-terior and midpoint of anterior and posterior vocal folds.Conclusion: Routinely used clinical methods of airway assessment lack sensitivity and specificity. Ultrasound can visualize anatomical structures in the supraglottic and subglottic views and is encouraging as an airway assess-ment tool.