eFAST Lung Views: Does my patient have a pneumothorax?
Recall, the parietal pleura covers the surface of the thorax and the visceral pleura covers the lungs. The presence of these moving against one another produces lung sliding on ultrasound.
Lung Probe Position and Hand Placement
- Point your indicator towards the patient’s head.
- Place your probe at the mid-clavicular line at the 2nd intercostal space of the right and left lungs respectively. This point is the most sensitive spot for looking for pneumothorax in the supine patient.
- Anchor your probe in the space between two ribs and set the ultrasound machine depth to 3-5cm.
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.
Identify Lung Sliding
- The next finding you will want to look for is lung sliding during respiration.
- 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.”
- “Ants Marching” sign is produced from the visceral and parietal pleura moving against one another during respiration.
- 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 a pneumothorax.
Although looking for lung sliding using B-Mode is usually sufficient, you can also consider assessing for a pneumothorax using M-mode.
Identify 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.
- Place the ultrasound machine in M-Mode (M-Mode for motion)
- Place the ultrasound doppler indicator/cursor over the lung field (NOT over the rib).
- Look for the normal “Seashore Sign“: Sky = Skin/Subcutaneous Tissue, Ocean= Muscle, Beach = Lung sliding motion (sandy appearance). The Seashore Sign is a NORMAL finding.
- Contrast this with the Barcode sign (see in eFAST pathology section below).