Lung imaging has traditionally been done using x-ray, CT scans or MRI. But, now we are seeing an increasing use of ultrasound to image the lungs, fueled by COVID-19. Early in our ultrasound education, we were taught that the lungs were not conducive to ultrasound imaging because they are air-filled structures, although we did scan to localize fluid for thoracenteses. Ultrasound can be used as a point-of-care (POCUS) modality in the emergency department as a triage tool for COVID-19 patients presenting with pneumonia-like symptoms, as a bedside exam for monitoring patients with pneumonia and for managing ventilation. The advantages of ultrasound are that it can be done bedside, it is in real time, it can be done fairly quickly and can distinguish between different lung conditions. The challenge, however, is that sonographers have little training in this exam. So, here is some information that might fill that gap.
Your transducer choice and exam preset will depend on the patient’s body habitus. These will range from convex to sector array and from abdomen to adult heart pre-sets. A single focal zone should be set at the pleural line, and the gain setting should avoid saturation. There are various scanning protocols such as the Bedside Lung Ultrasound in Emergency (BLUE) and the Fluid Administrations Limited by Lung Sonography (FALLS). If possible, the patient is scanned in a seated position and 14 views are suggested. These include 3 posterior, 2 lateral and 2 anterior views. Ultrasound findings for COVID-19 include thickened pleural lines and B-lines in the early stages. Late-stage findings also include small consolidations that can progress to lobal consolidations and (rarely) pleural effusions.
An article in the Journal of Ultrasound in Medicine, April 2020, suggests that the lung ultrasound score (LUS or LUSS) used in ICU patients with adult respiratory syndrome might be a valuable tool in assessing the severity of lung disease in patients with COVID-19. This system uses a point scoring system based on region and ultrasound pattern. This system can follow the changes in lung aeration thus reducing the need for chest radiographs and CT scans. (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0236312)
Ultrasound findings include hypoechoic focus that represents pleural consolidation, pleural thickening and discontinuity of the pleural line. Kerley b lines, another finding, are thin, 1-2 cm. long lines that are perpendicular to the pleural surface and extend out to it.