Emergency Medicine · Year 3 · from Emergency Medicine
Case 3: Lung Ultrasound - Differentiating Dyspnea
Patient Demographics
- Age: 68 years
- Sex: Male
- Occupation: Retired firefighter
Chief Complaint
"I can't breathe - it came on suddenly."
History of Present Illness
A 68-year-old male presents with acute onset dyspnea that began 1 hour ago. He was sitting watching TV when he suddenly felt severely short of breath. He has a history of CHF but reports this feels "different" - more sudden onset than his usual exacerbations. He also reports recent 5-day car trip (limited mobility). He denies chest pain, cough, or fever.
Initial Assessment
ESI Level: 2 - Acute respiratory distress
First Impression:
- Appearance: Anxious, moderate respiratory distress
- Work of breathing: Increased, using accessory muscles
- Circulation: Mildly tachycardic, not cyanotic
Vital Signs:
- Heart rate: 108 bpm
- Blood pressure: 142/88 mmHg
- Respiratory rate: 28 breaths/min
- SpO2: 88% on room air
- Temperature: 37.2C
- GCS: 15
Differential Diagnosis for Acute Dyspnea
- Pulmonary embolism (sudden onset, recent travel, prolonged immobility)
- CHF exacerbation (history of CHF)
- Pneumonia (less likely - no fever, cough)
- COPD exacerbation (possible)
- Pneumothorax (sudden onset)
Clinical Question: Is this CHF or PE? Treatment is very different!
Lung Ultrasound - Rapid Bedside Assessment
Equipment:
- Portable ultrasound
- Linear or curvilinear probe
- 8-zone or 12-zone protocol
Lung Ultrasound Findings:
| Finding | CHF | PE | Normal |
|---|---|---|---|
| A-lines | Rare | Common | Common |
| B-lines | Diffuse bilateral | Usually none | <3 per zone |
| Pleural sliding | Present | Present | Present |
| Consolidation | Possible | Possible (infarct) | None |
Examination Protocol (8-Zone)
Each Hemithorax:
- Upper anterior
- Lower anterior
- Upper lateral
- Lower lateral
Findings in This Patient
Right Lung:
- Upper zones: A-lines (normal air artifact), pleural sliding present
- Lower zones: A-lines, pleural sliding present, no B-lines
Left Lung:
- Upper zones: A-lines, pleural sliding present
- Lower zones: A-lines, pleural sliding present, no B-lines
Summary:
- Bilateral A-lines (horizontal reverberation artifacts = air)
- NO B-lines (no pulmonary edema)
- Pleural sliding present (no pneumothorax)
Interpretation: Normal lung ultrasound - NOT CHF
Additional Ultrasound Assessment
Cardiac Ultrasound:
- RV appears dilated (RV:LV ratio >0.9)
- Septal flattening ("D-sign")
- McConnell's sign: RV free wall akinesis with apical sparing
- IVC dilated, minimal collapse
DVT Ultrasound (Lower Extremity):
- Right common femoral vein: Non-compressible (DVT!)
- Right popliteal vein: Non-compressible (DVT!)
Integrated Findings
| Finding | Interpretation |
|---|---|
| Normal lung US (A-lines, no B-lines) | Not CHF |
| RV dilation + D-sign | Right heart strain (PE) |
| McConnell's sign | Highly specific for PE |
| DVT on compression US | Source of embolism |
Ultrasound Diagnosis: Pulmonary Embolism with RV strain
Confirmation
CT Pulmonary Angiography:
- Bilateral pulmonary emboli
- Large saddle embolus at main pulmonary artery bifurcation
- RV dilation on CT
Labs:
- Troponin: 0.18 ng/mL (elevated - RV strain)
- BNP: 890 pg/mL (elevated - RV strain)
- D-dimer: >5000 ng/mL
ECG:
- Sinus tachycardia
- S1Q3T3 pattern (classic but not sensitive)
- Right heart strain pattern
Risk Stratification
Submassive (Intermediate-High Risk) PE:
- Hemodynamically stable (not massive)
- RV dysfunction on imaging ✓
- Elevated troponin ✓
- Elevated BNP ✓
Treatment Decision:
- Anticoagulation (first-line)
- Consider thrombolytics if deteriorates
- Close monitoring in ICU
Management
Treatment:
- Heparin infusion (weight-based)
- ICU admission for monitoring
- Serial troponins and echos
- Remained stable
Transition:
- Switched to apixaban day 3
- Discharged day 5
- 3-month minimum anticoagulation (provoked PE)
- Hypercoagulable workup if unprovoked
Lung Ultrasound Patterns Summary
| Pattern | A-lines | B-lines | Sliding | Diagnosis |
|---|---|---|---|---|
| Normal | Yes | <3/zone | Yes | Normal |
| CHF | No | Diffuse bilateral | Yes | Pulmonary edema |
| Pneumonia | Variable | Focal | Yes | Consolidation pattern |
| Pneumothorax | Yes | None | NO | Absent sliding, lung point |
| This patient | Yes | None | Yes | Normal lungs (think PE) |
Teaching Points
- B-lines = fluid: Diffuse bilateral = CHF; focal = pneumonia
- A-lines = air: Normal finding OR dry lungs (dehydration, PE)
- Absent B-lines in dyspnea: Think PE, not CHF
- Lung US faster than CXR: Results in <5 minutes at bedside
- Integration is key: Combine lung US, cardiac US, DVT US for PE diagnosis
- McConnell's sign: RV free wall akinesis with apical sparing - specific for PE
- RV:LV ratio: >0.9 suggests RV strain (PE, pulmonary HTN)
- Point-of-care = point-of-decision: Ultrasound guides immediate management
Clinical Image
Image Description: Side-by-side lung ultrasound images comparing normal A-lines (horizontal reverberation artifacts indicating air) with pathological B-lines (vertical hyperechoic artifacts extending from pleura to screen edge indicating pulmonary edema).
Attribution: Image from Wikimedia Commons, Lung ultrasound B-lines. Licensed under CC BY-SA 4.0. Source: https://commons.wikimedia.org/wiki/File:LungUltrasoundBLines.jpg