Is Ultrasound a Valid and Reliable Imaging Modality for Airway Evaluation?: An Observational Computed Tomographic Validation Study Using Submandibular Scanning of the Mouth and Oropharynx
This work was supported by departmental funding. Drs Abdallah and Chin are also supported by the Merit Award Program, Department of Anesthesia, University of Toronto. Dr Vincent Chan received equipment support from BK Medical Systems (Wilmington, MA), Philips Medical Systems (Bothell, WA), SonoSite (Bothell, WA), and Ultrasonix (Richmond, BC, Canada). None of the other authors report any conflicts of interest. Portions of this report were presented as an abstract at the 38th annual meeting of the International Anesthesia Research Society, May 17–20, 2014, Montreal, Quebec, Canada. The abstract won the “Best of Category” award in the Airway Management category. Drs. Faraj W. Abdallah and Eugene Yu contributed equally to this work. The authors thank Mr. Cyrus Tse, Research Assistant, University Health Network, Toronto, Canada.
Ultrasound (US) imaging of the airway may be useful in predicting difficulty of airway management (DAM); but its use is limited by lack of proof of its validity and reliability. We sought to validate US imaging of the airway by comparison to CT-scan, and to assess its inter- and intra-observer reliability. We used submandibular sonographic imaging of the mouth and oropharynx to examine how well the ratio of tongue thickness to oral cavity height correlates with the ratio of tongue volume to oral cavity volume, an established tomographic measure of DAM.
A cohort of 34 patients undergoing CT-scan was recruited. Study standardized assessments included CT-measured ratios of tongue volume to oropharyngeal cavity volume; tongue thickness to oral cavity height; and US-measured ratio of tongue thickness to oral cavity height. Two sonographers independently performed US imaging of the airway before and after CT-scan.
Our findings indicate that the US-measured ratio of tongue thickness to oral cavity height highly correlates with the CT-measured ratio of tongue volume to oral cavity volume. US measurements also demonstrated strong inter- and intra-observer reliability.
This study suggests that US is a valid and reliable tool for imaging the oral and oropharyngeal parts of the airway, as well as for measuring the volumetric relationship between the tongue and oral cavity, and may therefore be a useful predictor of DAM.