Purpose: evaluate for etiology of respiratory failure- pleural fluid collections, pneumothorax, infiltrate, pulmonary edema.

Probe

• Linear for visualization of superficial structures- for example, the pleural interface to evaluate for lung sliding

• Curvilinear or phased array for the remainder of the lung

Findings

A and B Lines

• A-lines- *normal finding*. Hyperechoic arcs parallel to the pleural line. These are seen at intervals that are the same as the interval from the skin to the pleural line. Absence of A lines= change in attenuation coefficient of the lung (edema, consolidation).

• B-lines- vertical hyperechoic lines, caused by fluid-filled intra-lobular or interlobular septa touching the visceral pleural s­urface. Examples: cardiogenic pulm edema, ALI, ARDS, pneumonia, ILD or pulm fibrosis, pulm contusion.

• Comet tail artifact- *normal finding*. Arise from the pleural line and only extend 2-4 cm deep before fading (unlike B lines). They mean that the pleura are in contact.

Pleural sliding

• Shimmering of the hyperechoic pleura→ pleura are in contact. No sliding→ concerning for PTX.

• There are clinical conditions other than PTX that result in a lack of lung sliding: Effusion, inflammatory adhesions, (pneumonia, ALI), pleurodesis, interstitial or fibrotic lung disease, pleural disease, apnea, severe hyperinflation (asthma, COPD), artifact (subQ air).

• M mode- sliding→ seashore. No sliding→ barcode.

Lung pulse- cardiac motion causes the two pleura to slide

Lung point- the junction between the edge of the pneumothorax and the normal lung, where the pleural surfaces meet. One side is sliding and the other side isn’t.

Consolidation

• Air bronchograms- air in small aerated patches of the consolidated lung, or the small bronchi. Dynamic- bubbles move in and out with each breath- no complete bronchial obstruction, more likely true consolidation vs atelectasis.

• Pneumonia- advanced consolidation (air is completely replaced with fluid)→ lung appear to have a liver-like echogenicity (hepatization)

Diaphragm- evaluate diaphragm contraction and thickness.

Effusions

• Spine sign- the presence of a large effusion allowing visualization of the spine. Normally the air in the lung prevents visualization of the spine above the level of the diaphragm, but sound waves can pass through the fluid.

• Plankton sign- floating debris in an effusion that swirl with pulm or cardiac motion→ blood/ fibrin suggestive of HTX/ exudate

• Jellyfish sign- consolidated or compressed lung is floating in the pleural fluid.

Common Pathologies with their associated ultrasound findings

• PTX- no lung sliding, M-mode barcode sign, lung point sign, A-lines from intact parietal pleura

• Pulmonary edema- B lines, normal lung sliding, +/- effusions

• ARDS- B lines, normal lung sliding

References

• Lung Ultrasound Made Easy: Step-By-Step Guide

• Lee FC. Lung ultrasound-a primary survey of the acutely dyspneic patient. J Intensive Care. 2016 Aug 31;4(1):57.