Airways ultrasound in predicting difficult face mask ventilation

Abstract

Unanticipated difficult airway is a potentially life-threatening event during elective surgery or management of critical conditions. Nevertheless, predicting difficult mask ventilation currently remains a challenge due to the poor sensitivity of available clinical tests. Our primary goal was to verify whether preoperative upper airway ultrasound measurements were useful to predict difficult face mask ventilation. Our secondary goal was to evaluate clinical characteristics and differences between patients who are difficult to ventilate and patients who are not. We performed a prospective observational study, enrolling 250 adult patients selected for colorectal, gastric, bariatric and pancreatic elective surgery between September 2017 and October 2018. We performed a preoperative US assessment of the airways, following a standardized protocol. We measured the hyomental distance (DIM), the thickness of the base of the tongue (SBL), the thickness of the soft tissues anterior to the hyoid bone (STTi), thyro-hyoid distance (DTI), the thickness of soft tissue anterior to the epiglottis (STTe), to the arytenoid (STTa) and to the commissure of the vocal cords (STTcv). SBL had a predictive role of difficult mask ventilation in curarized and noncurarized patients for values higher than 50 mm. Hyomental distance with hyperextension of the head and subluxation of the mandible (DIMs) had a predictive role in the curarized patient (protective parameter). Airways ultrasound evaluation could be an important tool to predict difficult mask ventilation. Further studies are necessary to validate the parameters found and correlate them to the preoperative clinical evaluation.