BY: MAX RUBINSTEIN, MD
The Case: A 5 year old previously healthy boy presents to the ED with three days of fever and progressive shortness of breath. His exam is notable for course rhonchi and decreased aeration in the right anterior lung. There was no personal or family history of asthma, eczema, or food allergies. He received an albuterol nebulizer with no effect.
The Diagnostic Intervention: Lung Ultrasound
Point of Care Lung Ultrasound:
Point of care lung ultrasound is highly useful in detecting pulmonary pathology commonly encountered in the emergency department, most notably pneumothorax, pulmonary edema, and pneumonia. The basic technique of lung ultrasound in children is the same no matter what underlying process is suspected. The linear probe is used and oriented perpendicular to the rib in the longitudinal axis. This allows detailed visualization of the pleural line. This is perhaps the most important aspect of lung ultrasonography as 90% of respiratory dysfunction attributable to the lungs affects the pleura.1 Differences in the appearance of the pleural line help the clinician distinguish between causes of respiratory distress. There are several techniques described to adequately assess the lungs by ultrasound, the simplest of which is to image at three interspaces in the midclavicular, mid-axillary, and posterior lung fields.1,2
Figure 1. Normal Lung Anatomy on Ultrasound
Pneumonia on Ultrasound:
Pneumonia on lung ultrasound has a characteristic appearance. One can see “hepatization” of the lung as this normally echogenic and artifact filled tissue (see Figure 1) becomes echo-poor and increasingly tissue-like, resembling the liver on ultrasound (see Figure 2). This is accompanied by “dynamic air bronchograms,” a branching lesion that courses through affected lung and moves with breathing. 3 This mobility helps distinguish pneumonia from atelectasis. A recent study found that dynamic air bronchograms have a 97% positive predictive value for pneumonia.4
How good is lung ultrasound for detecting pneumonia?
- Sensitivity & Specificity in children > 90%5
- When performed by emergency medicine physicians who have received a 1 hour training session, sensitivity drops to 86% but specificity is 97%.6
- Ultrasound may also be better at detecting small pneumonias than standard chest x-ray.6 However, the clinical significance of this finding has yet to be determined.