Module · Lung
FUSIC Lung resources
30 scans, 10 directly observed, max 10 normals. Six zones per side. Additional competency: guided thoracocentesis (doctors). The logbook includes a site for drainage identification.
Probe selection & six-zone techniqueWhich probe, how to hold it, and where to place it — the systematic approach.
Use a curvilinear or phased-array probe, 2–5 MHz, orientated longitudinally (cephalad–caudad). The probe marker points toward the patient’s head. Place perpendicular to the ribs — rib shadows should appear on both sides of the image (bat sign).
Six examination points per side (12 total):
- Right/Left upper anterior: 2nd–3rd ICS, midclavicular line
- Right/Left lower anterior: 4th–5th ICS, midclavicular line
- Right/Left posterolateral: Posterior axillary line, above diaphragm
At each point identify: subcutaneous tissue → ribs (acoustic shadow) → pleura (bright hyperechoic line) → lung artefacts below.
Normal lung: A-lines & pleural slidingThe foundation for interpreting everything else.
Pleural sliding: The visceral and parietal pleura slide against each other with breathing. On 2D: shimmering movement at the pleural line. On M-mode: the seashore sign — granular (sandy) pattern deep to the pleural line (lung in motion) with horizontal lines superficially (chest wall at rest).
A-lines: Horizontal reverberation artefacts at equal intervals deep to the pleural line. A-lines + pleural sliding = normal aeration at that point.
Lung pulse: In intubated patients, cardiac pulsations transmitted through the lung produce subtle movement at the pleural line. Its presence rules out pneumothorax at that point.
B-lines & interstitial syndromeVertical artefacts indicating alveolar-interstitial pathology.
B-lines arise from the pleural line, extend vertically to the bottom of the screen without fading, and move with the pleural line. They obliterate A-lines where they appear.
| Pattern | Interpretation |
|---|---|
| <3 B-lines per zone | Normal (especially posterolaterally) |
| ≥3 B-lines, unilateral | Focal — pneumonia, contusion |
| Bilateral multiple B-lines | Interstitial syndrome — oedema, ARDS, ILD |
| Confluent B-lines (white lung) | Severe interstitial syndrome |
Consolidation & atelectasisTissue-like appearances, dynamic vs static air bronchograms.
Consolidated lung appears tissue-like (hepatised) — similar echogenicity to liver or spleen. The normal reverberant artefact pattern is replaced by a solid-tissue appearance.
Air bronchograms: Bright tubular structures within consolidated lung — air-filled bronchi.
- Dynamic air bronchograms (moving centrifugally on inspiration): strongly suggests pneumonia. PPV ~97% for active infection.
- Static air bronchograms: More consistent with obstructive atelectasis.
Pleural effusion — recognition, sizing & guided drainageThe additional competency: identifying the right site for thoracocentesis.
Echo-free space above the diaphragm, posterior to the lung. Best in posterolateral zones.
Sinusoid sign (M-mode): Respiratory variation in the distance between lung and chest wall. Sinusoidal = effusion. No movement = pleural thickening.
Volume estimation: Rough guide — 1 cm depth ≈ 100 ml. Floating lung = likely >500 ml.
Differentiating from subdiaphragmatic fluid: The diaphragm is the key landmark. Pleural fluid is above it; abdominal fluid is below. Liver/spleen lies between abdominal fluid and the diaphragm.
Transudate vs exudate: Not reliably distinguished on ultrasound. Echogenic/septated fluid may suggest exudate but biochemical analysis is required.
Guided thoracocentesis (doctors — additional FUSIC Lung competency):
- Scan the patient in the position for the procedure (sitting forward or semi-recumbent)
- Identify the deepest dependent pool of effusion
- Use colour Doppler to check for vessels at the proposed insertion point — intercostal artery runs in the subcostal groove; aim just above the upper rib margin
- Measure the depth from skin to pleural space
- Mark the site; do not reposition the patient after marking if using a static technique
- Real-time guidance is preferred for all procedures in FUSIC Lung training
PneumothoraxAbsent sliding, barcode sign, and the definitive lung point.
Ultrasound is more sensitive than CXR for pneumothorax, particularly in the supine ventilated patient where air collects anteriorly.
Findings suggesting pneumothorax:
- Absent pleural sliding at that point
- Absent B-lines (B-lines cannot coexist with pneumothorax)
- Barcode sign on M-mode: horizontal lines throughout, above and below the pleural line — granular sandy pattern absent
- A-lines present + absent sliding: high specificity combination
Lung point (definitive, specificity ~100%): The point where aerated lung meets the pneumothorax. Sliding lung on inspiration, absent sliding on expiration — a flickering appearance at the border. Fan laterally and posteriorly to find it.
Pitfalls & limitationsWhen lung ultrasound misleads.
- Surgical emphysema: Subcutaneous air causes artefacts preventing pleural line identification. All findings uninterpretable.
- Obesity/thick chest wall: Reduce depth and try lower frequency.
- Pleural thickening: Can resemble small effusion. Sinusoid sign: thickening has no sinusoidal variation.
- Post-pleurodesis: Absent sliding without pneumothorax. No lung point will be found.
- Over-reliance on anterior zones: Posterior pathology will be missed. Always scan posterolaterally in ICU patients.
- B-lines post-cardiac surgery: Common from volume overload, atelectasis, effusions. Careful interpretation required.