3. Lung Ultrasound Protocol

Step 1: Lung ultrasound of Anterior chest (R1/L1)

Point 1 (R1 and L1) assesses the anterior chest. This point will be most relevant when assessing for pneumothorax and/or interstitial edema.

  • Point your indicator towards the patient’s head.
  • Place your probe at the mid-clavicular line at the 2nd intercostal space of the right (R1) and left (L1) lungs respectively
  • Anchor your probe in the space between two ribs.
R1 Point - Lung Ultrasound Midclavicular Line
R1 Ultrasound Probe Position

Identify Two Rib Shadows (Batwing Sign)

  • The first lung ultrasound finding to confirm you are in the correct position is to look for the two rib shadows or the “Batwing Sign.” This ensures that your probe is in between two ribs.
Batwing Sign on Ultrasound

Identify Lung Sliding

  • The next finding you will want to look for is lung sliding.
  • Lung sliding is a normal finding where the visceral and parietal pleura slide back and forth on one another as the patient breathes. Some say this looks like tiny “ants marching on a line.”
  • This is a simple finding but extremely useful since lung sliding definitely means that the visceral and parietal pleura are next to each other, effectively ruling out pathology such as pneumothorax.

Editor’s Note: Lung sliding can be seen with the phased array and curvilinear ultrasound probes. However it is often times most easily seen with the linear probe given how shallow it is.

Ultrasound Lung Sliding with Linear Probe
Lung sliding with linear probe

Lung Sliding using M-Mode (Optional)

  • If lung sliding is not readily apparent, it can be further be evaluated using M-Mode. The goal of M-Mode is to see if the patient has a normal seashore sign.
  • Seashore Sign: Sky = Skin/Subcutaneous Tissue, Ocean= Muscle, Beach = Lung sliding motion (sandy appearance)
Lung ultrasound Seashore Sign - Sky, Ocean, Beach
Seashore Sign on Lung Ultrasound

Identify A-lines

When you angle your probe perpendicular to the pleura, ultrasound waves reflect off the air from the pleura and the probe surface, producing an image of what looks like pleural lines that lie equidistant to the true pleural line. These reverberation artifacts can continue reflecting back and cause several A-lines to appear before dissipating. (A1 = first A-line seen, A2 = second A-line seen, A3 = third A-line seen)

Ultrasound Reverberation Artifact - Lung A-lines
A-lines with Lung Sliding Labeled

Clinically, A-lines can indicate healthy aeration of the alveoli. However, A-lines can also be seen in cases of pneumothorax since there will be a reflection of air at the parietal pleura. The difference is that you will not see lung sliding in pneumothorax.

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