Dynamic Air Bronchogram on Lung Ultrasound
Definition:
A dynamic air bronchogram refers to the movement of air within the bronchi that is visible on ultrasound. It typically appears as hyperechoic (bright) lines or dots that move within a hypoechoic (dark) background representing consolidated lung tissue.
Clinical Significance:
- **Pneumonia:** Dynamic air bronchograms are most commonly associated with pneumonia. They indicate that there is still air movement within the bronchi, despite the surrounding lung tissue being consolidated (filled with fluid, inflammatory cells, or pus). This finding supports the diagnosis of an infectious process rather than atelectasis.
- **Atelectasis:** In contrast, static air bronchograms (non-moving) are often seen in atelectasis, where the airways collapse and air movement is absent.
Ultrasound Characteristics:
- **Dynamic Nature:** The key feature is the movement of air within the bronchi during respiration, which distinguishes dynamic from static air bronchograms.
- **Appearance:** Hyperechoic linear or dot-like structures within consolidated lung areas that move synchronously with the patient's breathing.
Clinical Utility:
- **Diagnosis:** The presence of dynamic air bronchograms is a useful diagnostic feature for distinguishing pneumonia from other causes of lung density, such as atelectasis or pleural effusion.
- **Monitoring:** It can also be used to monitor the progression or resolution of pneumonia, as the air bronchograms will change with the amount of air and fluid in the bronchi and alveoli.
Procedure:
- **Technique:** Using a linear or curvilinear ultrasound probe, the sonographer examines the lung fields, particularly focusing on areas of suspected consolidation. The patient is asked to breathe deeply to observe the movement of the air bronchograms.
- **Positioning:** Patients can be scanned in various positions (supine, lateral decubitus, sitting) depending on the clinical scenario and areas of interest.
Summary
Dynamic air bronchograms on lung ultrasound are indicative of the presence of air movement within the bronchi amidst consolidated lung tissue, commonly seen in pneumonia. This dynamic finding helps differentiate pneumonia from atelectasis, where air bronchograms are static. Recognizing and interpreting dynamic air bronchograms can significantly aid in the accurate diagnosis and management of respiratory conditions.
**References:**
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4541160/
2. https://www.atsjournals.org/doi/full/10.1164/rccm.201407-1279CI