Approach: Multiple conventions exist (6, 8, up to 18 zones)
Position: Position the patient upright, if possible
Steps to Scan:
Place the probe perpendicular to the chest wall between the ribs, with the indicator pointing toward the patient’s head
Scan the anterior, lateral, and posterior lung fields.
In each rib space, sweep/ fan to assess for A-lines (horizontal) and B-lines (vertical)
Repeat bilaterally across all lung zones for a comprehensive assessment.
Lung Scanning Zones:
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.
1. Lung Sliding
Lung sliding (often described as ”ants marching on a line”)” is a normal finding seen when the visceral and parietal pleura slide over each other during respiration. Its presence rules out pneumothorax at the scanned site, with near 100% sensitivity. See video above!
Absent or reduced sliding may be due to:
Pneumothorax (air)
Pleural effusion (fluid)
Severe COPD or lung hyperinflation
⚠️ Lung sliding rules out pneumothorax at the site, but absence is not specific. Interpret with clinical context.
2. Curtain Sign
The curtain sign is seen in healthy, aerated lungs at R3/L3 (PLAPS position). During inspiration, the lung sweeps down and temporarilyobscures the diaphragm, liver, or spleen. These structures reappear during exhalation.
3. A-lines
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.
4. B-lines
B-lines are vertical artifacts caused by thickened or fluid-filled lung tissue. They are non-specific and can be seen in pulmonary edema, interstitial lung disease, pneumonia, and other conditions.
Scattered B-lines suggest early or mild fluid accumulation
Confluent B-lines (merged vertical lines) indicate more advanced fluid overload
≥3 B-lines in one interspace is considered pathologic