Approach to Dyspnea
A board-focused framework for dyspnea that sorts patients into cardiac, pulmonary, and other causes and drives the next-best-step from vitals, ECG, CXR, BNP, D-dimer, and troponin. It anchors on classic vignette clues (orthopnea/PND, sudden pleuritic pain, Kussmaul breathing) and on when to stabilize before imaging.
Framing the Dyspneic Patient
Dyspnea is the subjective sensation of uncomfortable breathing. On the boards your job is to sort it into cardiac, pulmonary, or other (anemia, metabolic acidosis, anxiety, deconditioning) and to separate acute (minutes–hours: PE, pneumothorax, flash pulmonary edema, anaphylaxis, ACS, asthma/COPD flare) from chronic (weeks–months: HF, COPD, interstitial lung disease, obesity, anemia).
Start every vignette with ABCs and pulse oximetry — a failing airway, hypoxia, or hemodynamic collapse triggers immediate stabilization before any imaging. The highest-yield first-line tests are ECG, chest X-ray, and, when the story fits, BNP, troponin, and D-dimer.
Two orienting questions unlock most cases: How fast did it start? and What are the vitals and SpO2? Sudden, unilateral, pleuritic dyspnea points to PE or pneumothorax; orthopnea and paroxysmal nocturnal dyspnea (PND) point to heart failure; wheeze points to obstructive lung disease; stridor points to upper-airway obstruction.
- BNP < 100 pg/mL makes acute HF unlikely; > 400 pg/mL supports it (100–400 = gray zone). (NT-proBNP uses higher, age-adjusted cutoffs.)
- PE workup: low pretest probability → D-dimer; positive D-dimer or high probability → CT pulmonary angiography (use V/Q scan if renal failure or contrast allergy).
- Wells low + PERC all negative → no further PE testing needed.
- Dyspnea + clear lungs + hypoxia → think PE; dyspnea + clear lungs + normal SpO2 → anemia or metabolic acidosis (Kussmaul breathing in DKA).
- A–a gradient: normal in pure hypoventilation (opioids, obesity hypoventilation) and at high altitude; elevated with V/Q mismatch, shunt, or diffusion defect (PE, edema, pneumonia).
- Orthopnea + PND + S3 + bilateral crackles + JVD = left heart failure.
- Sudden pleuritic pain + unilateral absent breath sounds + hyperresonance = pneumothorax; add hypotension + tracheal deviation → tension → immediate needle/finger decompression, do NOT wait for CXR.
- Wheeze = lower airway (asthma/COPD, or cardiac 'asthma' from HF); stridor = upper airway.
Acute Dyspnea: Cause → Clue → Test → Step
| Cause | Classic clue | Key test | Next step |
|---|---|---|---|
| HF / flash edema | Orthopnea, PND, JVD, S3, crackles | BNP↑, CXR edema | Loop diuretic, O2, nitrates |
| PE | Sudden pleuritic dyspnea, tachycardia, clear lungs | D-dimer / CTPA | Anticoagulation (thrombolyse if hemodynamically unstable) |
| Pneumothorax | Sudden unilateral pain, absent breath sounds, hyperresonant | Upright CXR | Chest tube; tension → needle decompression first |
| COPD / asthma flare | Wheeze, prolonged expiration, smoker/atopy | Clinical ± spirometry | Bronchodilators + steroids |
| Pneumonia | Fever, productive cough, focal consolidation | CXR | Antibiotics |
| Tamponade | Beck triad, pulsus paradoxus, electrical alternans | Echocardiogram | Pericardiocentesis |
| Anemia / DKA | Pallor/fatigue; or fruity breath, Kussmaul, clear lungs | CBC; glucose + ABG | Treat underlying cause |
Vignette: A 68-year-old man wakes at 3 AM gasping, must sit upright, and sleeps on three pillows. Exam: bilateral basilar crackles, JVD, S3 gallop, pitting edema. CXR shows cephalization and Kerley B lines. → Dx: Acute decompensated left heart failure (cardiogenic pulmonary edema). → Next step: IV loop diuretic (furosemide) + supplemental O2; add nitroglycerin for hypertensive flash edema. Order BNP, troponin, ECG, and echocardiogram.
Vignette: A 25-year-old tall, thin man develops sudden right-sided pleuritic chest pain and dyspnea. Exam: absent breath sounds and hyperresonance on the right, trachea midline, vitals stable. → Dx: Primary spontaneous pneumothorax. → Next step: Upright CXR to confirm; small/stable → O2 + observation, large/symptomatic → chest tube (needle aspiration is an alternative). If he becomes hypotensive with tracheal deviation → tension pneumothorax: immediate needle/finger thoracostomy without waiting for imaging.
Vignette: A 55-year-old woman 5 days after total knee replacement has abrupt dyspnea and pleuritic pain. HR 118, SpO2 89%, lungs clear. ECG: sinus tachycardia (the classic S1Q3T3 pattern is actually uncommon). → Dx: Pulmonary embolism. → Next step: High pretest probability → go straight to CT pulmonary angiography (skip D-dimer). Start anticoagulation empirically if no bleeding risk. Hemodynamic instability/hypotension (massive PE) → thrombolysis; a submassive PE (RV strain but normotensive) is generally anticoagulated with close monitoring, not routinely thrombolysed.
Vignette: A 19-year-old with type 1 diabetes has deep, rapid breathing, fruity breath, and clear lungs; glucose 480, pH 7.15. → Dx: DKA with Kussmaul respirations (respiratory compensation for metabolic acidosis). → Next step: IV fluids, insulin infusion, and potassium repletion (check K+ before starting insulin) — the 'dyspnea' resolves by correcting the acidosis, not the lungs.
Pearl: Dyspnea + clear lungs + low SpO2 → PE; dyspnea + clear lungs + normal SpO2 → anemia or acidosis.
'ABCDE' — the chest X-ray findings of cardiogenic pulmonary edema / heart failure:
- A — Alveolar edema (perihilar 'bat-wing' opacities)
- B — Kerley B lines (interstitial fluid in septa)
- C — Cardiomegaly (cardiothoracic ratio > 0.5 on PA film)
- D — Dilated upper-lobe vessels (cephalization)
- E — pleural Effusions
Seeing these on a vignette CXR = heart failure until proven otherwise → check BNP and start a loop diuretic.
- Unstable first: hypoxia → O2; failing airway → intubate; suspected tension pneumothorax or anaphylaxis → treat before imaging (needle decompression / IM epinephrine).
- Acute + pleuritic + clear lungs → rule out PE (Wells → D-dimer vs CTPA) and pneumothorax (CXR).
- Acute + wet lungs (crackles, JVD, orthopnea) → HF: BNP, diuresis, echo.
- Wheeze → asthma/COPD flare → bronchodilators + steroids.
- Fever + focal consolidation → pneumonia → antibiotics.
- Normal CXR + normal SpO2 + normal ECG → look outside the chest: anemia (CBC), metabolic acidosis/DKA (glucose, ABG), or anxiety/hyperventilation (diagnosis of exclusion).
- Chronic dyspnea workup: CXR, spirometry (PFTs), BNP, CBC, and echocardiogram sort HF vs COPD vs ILD vs anemia.
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