Published February 2021
1 Chief Medical Resident, Internal Medicine, University of Colorado. 2 Fellow, Pulmonary and Critical Care Medicine, University of Colorado
Identify an air bronchogram on a chest x ray
Describe why an alveolar filling process can lead to the appearance of air bronchograms on a chest x ray.
Plan to spend 5-10 minutes familiarizing yourself with the animations of the PowerPoint and the key findings of this chest x-ray.
Present the image either by expanding the window (bottom right) in a browser or downloading the PowerPoint file (downloading is recommended). Have the image pulled up in presenter mode before learners look at the screen to avoid revealing the diagnosis. Ask a learner to provide an overall interpretation. Then advance through the animations to prompt learners with key questions and reveal the findings, diagnosis, and teaching points.
Instructions: Ask a leaner to provide an overall interpretation. Advance using the arrows or scroll wheel on the mouse reveal subsequent questions with answers and graphics. You can go back to prior graphics and questions by using the back arrow or scrolling back on the mouse wheel.
Official CXR Read: Endotracheal tube, enteric tube, and ECMO cannula remain in place. Swan-Ganz catheter tip projects over the main pulmonary trunk.
There is complete opacification of both hemithoraces, obscuring both hemidiaphragms and heart borders. Small right pleural effusion is present. Widespread air bronchograms are present.
Diagnosis: Rapidly progressive interstitial lung disease associated with dermatomyositis leading to refractory hypoxemic respiratory failure necessitating ECMO
Teaching: On the normal chest x-ray, we can visualize the trachea and proximal bronchi but not the distal airways. We are able to see the air in the trachea and proximal bronchi because they are surrounded by the soft tissue of the mediastinum, which are a different density. In the lungs, both airways and alveoli are filled with air and are thus, indistinguishable on chest x-ray.
Where there are dense alveolar filling processes, this creates a contrast between the density of material in the alveoli (blood, pus, fluid, or protein) and in the airways (air). This allows visualization of the airways leading to air bronchograms.
Take Home Points
An air bronchogram refers to the phenomenon in which air-filled airways are made visible on a radiograph due to a contrast in density with consolidated alveoli.
The presence of air bronchograms suggests a dense alveolar filling process (for example, lobar pneumonia).
Goodman LR. The Air Bronchogram Sign. Feldman's Principals of Chest Roetgenology. Fifth Edition. Elsevier, 2021, pp 112-125.