Lung Assessment

---

Probe(s): Curvilinear or Phased array

Preset: Lung or abdominal

Approach: Multiple conventions exist (6, 8, up to 18 zones) 

1. Position the patient upright if possible. 
2. Place the probe perpendicular to the chest wall, between the ribds, with the the indicator towards the patient’s head
3. Scan the anterior, lateral, and posterior lung fields. 
4. In each rib space, sweep or fan the probe to assess for A-lines (horizontal) and B-lines (vertical)
5. Repeat bilaterally in all lung zones for a full assessment.

• Anterior Chest Scan: Place the probe at the 2nd intercostal space, mid-clavicular line, corresponding to R1 and L1.
• Lateral Chest Scan: Place the probe at the 6th–7th intercostal space, mid-axillary line, corresponding to R2 and L2. This is typically just lateral to the nipple line in males or at the same level in females.
• Posterior Chest Scan: Place the probe at the posterior axillary line between the 10th–12th ribs. Identify key landmarks: liver (right), spleen (left), kidney, and diaphragm.

Lung sliding (”ants marching on a line”) is a normal finding that occurs when the visceral and parietal pleura slide over each other during respiration. Its presence rules out a pneumothorax in the scanned area, with near 100% sensitivity. 

• Absent or reduced sliding may be due to: pneumothorax (air), pleural effusion (fluid) or severe COPD or lung hyperinflation. 
• Lung sliding rules out pneumothorax at that site, but absence is not specific to pneumothorax

The curtain sign is seen in healthy, aerated lungs at R3/L3 (PLAPS position). During inspiration, the lung sweeps down and temporarily obscures the diaphragm, liver, or spleen. These structures reappear during exhalation.

A-lines are horizontal artifacts seen when the probe is perpendicular to the pleura, caused by reflection of ultrasound waves off air at the pleural surface. In a pneumothorax, A-lines are often present, but lung sliding is absent, which helps distinguish it from normal lung.

B-lines are vertical artifacts caused by thickened or fluid-filled lung tissue.  They are non-specific, seen in pulmonary edema, interstitial lung disease, pneumonia, etc. Scattered B-lines suggest early fluid accumulation, while confluent B-lines (vertical lines merge into a continuous band) indicate more advanced overload.

• ≥3 B-lines in one interspace is considered pathologic
• Tip: A-lines = horizontal; B-lines = vertical.