Clinical Review

Emergency Ultrasound: Lung Assessment

Lung ultrasound takes 2 to 3 minutes to perform and can help narrow down the differential in a patient with dyspnea.

Use of this imaging modality at bedside can quickly assess the dyspneic patient, facilitating treatment.


 

References

Lung ultrasound can be a valuable addition to the emergency physician’s (EP’s) diagnostic armamentarium. This article reviews how this modality may be used to differentiate between chronic obstructive pulmonary disease (COPD) and coronary heart failure (CHF) exacerbations. As patients often have a history of both of these diseases, it is difficult to distinguish which condition is the cause of a patient’s dyspnea. This examination is easy to learn and in most cases, it can be performed within 3 to 4 minutes. Most importantly, lung ultrasound can assist in making clinical decisions in real time at the bedside. Although the following is not a comprehensive review, it does provide the basic essentials, allowing the clinician to begin using this modality in the ED.

Getting Started

The curvilinear probe is required to perform ultrasound of the lungs. Most studies divide the lung into regions, though consensus on exactly how many regions are required remains unclear. The blue protocol, which is probably the most well-known study, divides the lung into the anterior, lateral, and posterolateral sections.1 The superior and inferior aspects of each zone are evaluated with a total of six ultrasound views
per lung.

Artifacts

An understanding of artifacts is essential to correct interpretation of the ultrasound images. Two ultrasound findings of normal lungs are “A lines” and “lung sliding.” However, these patterns are seen in normal lungs and in the lungs of patients with asthma and COPD.

Lung sliding is movement of the parietal pleura sliding against the visceral pleura. A lines are a repetitive reverberation artifact of the pleura (Figure 1). Occasional comet-tail artifacts—short hyperechoic artifacts that arise from the pleural line and descend in a vertical orientation partially down the screen (Figure 2).

B lines are the ultrasound equivalent of the Kerley B lines found on chest X-ray. Bilateral B lines are commonly present in lungs with interstitial edema. For an examination to be considered positive, there must be a minimum three B lines per view (Figure 3). Ultrasonographic B lines are long wide bands of hyperechoic artifact that have been likened to the beam of a flashlight. They originate at the pleural line and traverse the entire ultrasound screen vertically to the bottom of the screen. Causes of unilateral B lines can include pneumonia and pulmonary contusion. As the EP becomes more familiar in performing lung ultrasound, he or she will become more adept at identifying A and B lines.

Differential Diagnosis

When using ultrasound to differentiate between CHF and COPD, this examination has been shown to have a sensitivity of 100% and a specificity of 92%.2 By performing lung ultrasound immediately upon a patient’s arrival to the ED, the clinician can obtain quick and accurate insight into whether a patient would benefit from albuterol or nitroglycerin. In the acutely dyspneic patient, combining lung ultrasound with focused echocardiogram and sonographic inferior vena cava assessment will provide additional information to support the diagnosis.

Conclusion

As with other bedside imaging techniques, lung ultrasound in the ED can help to quickly assess the dyspneic patient and facilitate initiation of appropriate treatment.

Dr Taylor is an assistant professor and director of postgraduate medical education, department of emergency medicine, Emory University School of Medicine, Atlanta, Georgia. Dr Meer is an assistant professor and director of emergency ultrasound, department of emergency medicine, Emory University School of Medicine, Atlanta, Georgia. Dr Beck is an assistant professor, department of emergency medicine, Emory University School of Medicine, Atlanta, Georgia.

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