Role of ultrasound in airway assessment in the respiratory ICUs

Abstract

Background Airway evaluation and its management remain an emerging clinical science. Ultrasound (US) provides point-of-care dynamic views of the airway in perioperative, emergency, and critical care settings. Identification of a difficult airway before intubation allows for optimal preparation, equipment selection, and participation of experienced personnel. Objective The aim of this study was to evaluate the role of US in the assessment of airways and to determine whether US has the potential to serve as an effective, noninvasive method for the diagnosis of tracheomalacia. Patients and methods A prospective cross-sectional study was carried out on patients admitted at the respiratory ICU. US examination of the airways and diaphragm was performed together with either fiberoptic bronchoscopy (FOB) or dynamic expiratory computed tomography chest. Dynamic expiratory computed tomography chest and FOB were done within 24 h of US examination. Results A total of 53 patients were included. US could successfully confirm endotracheal tube (ETT) placement in all patients. ETT was endotracheal in 30 (94%) patients, whereas it was esophageal in two (6%) patients. Hyomental distance at a cut-off of up to 4.51 cm was a good predictor of difficult intubation with 100% sensitivity and 87.5% specificity. Subglottic airway transverse diameter was used as a predictor of ETT size. Patients with tracheomalacia by FOB had a significantly longer duration of mechanical ventilation. Lateral pharyngeal wall thickness was used as a predictor of obstructive sleep apnea, a new cut-off point was used at more than 4.1 cm in the intubated group of patients with 87.5% sensitivity and 95.8% specificity, whereas a cut-off point more than 4.2 cm in the nonintubated patients had 100% sensitivity and 100% specificity. In the intubated group, out of the seven cases diagnosed with tracheomalacia by FOB, five patients were missed by US with 40% sensitivity, whereas in the nonintubated group, the results were significantly better, where only one case was missed by US with 80% sensitivity. Conclusion US has many advantages for imaging the airway; it is safe, quick, repeatable, portable, widely available, and provides real-time dynamic images relevant for several aspects of management of the airway. Thus, it seems reasonable to consider the routine use of airway US in the ICU.