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Dyspnea, or shortness of breath, is a commonly reported symptom in acute care and outpatient settings. Causes of dyspnea include pulmonary (e.g., pneumonia, asthma exacerbation), cardiac (e.g., acute coronary syndrome, congestive heart failure), toxic-metabolic (e.g., metabolic acidosis, medications), and upper airway (e.g., epiglottitis, foreign body) pathologies. On initial presentation, it is important to immediately evaluate the patient for any urgent or life-threatening causes of dyspnea with patient history, physical examination, and diagnostic testing. Once immediately life-threatening causes are ruled out, a more detailed patient history should be obtained and further testing should be done to narrow the differential diagnoses.


Approach to management

  1. ABCDE survey
  2. Establish IV access, cardiac and pulse oximetry monitoring.
  3. Start supplemental oxygen as needed.
  4. Assess the need for ventilation support and airway management.
  5. Stabilize cardiovascular function (e.g., IV fluid resuscitation).
  6. Perform focused history, examination, and diagnostics to rule out life-threatening reversible causes (see “Diagnostics” below).
  7. Once life-threatening causes have been ruled out:
  8. Treat the underlying cause.

Red flags for dyspnea

Immediately life-threatening causes


The diagnostic workup should be guided by the pretest probability of the diagnoses under consideration. The following list includes some commonly used diagnostic tools that can help to diagnose or rule out possible etiologies in patients with acute dyspnea.

Initial workup [1]

Laboratory studies


  • ECG
  • Chest x-ray
  • CT chest with IV contrast (PE protocol)
  • TTE
  • FAST

Further diagnostics to consider

Pulmonary causes

Clinical features Diagnostic findings Acute management
Pneumonia [2]
COPD exacerbation (AECOPD) [3][4]
Asthma exacerbation [5]
  • See the acute management checklist for asthma exacerbation.
Tension pneumothorax [6][7]
Spontaneous pneumothorax [8][6][9]
  • Sudden, sharp unilateral chest pain
  • Acute dyspnea
  • Hypoxemia
  • Hyperresonance, decreased breath sounds on affected side
  • Crepitus
  • History of lung disease or trauma
Pulmonary embolism [10]
Acute chest syndrome [11][12]
ARDS [13][14]

Cardiac causes

Clinical features Diagnostic findings Acute management
Acute coronary syndrome [15][16]
  • ECG: nonspecific changes, ST-segment elevation/depression, T-wave inversions, Q waves
  • Increased or normal troponin
  • TTE: hypokinesis, regional wall motion abnormalities
Cardiac tamponade [17]
  • ECG: low voltage, electrical alternans
  • CXR: enlarged cardiac silhouette
  • TTE: circumferential fluid layer, collapsible chambers , high EF, dilated IVC
    • Inspiration: Both ventricular and atrial septa move sharply to the left.
    • Expiration: Both ventricular and atrial septa move sharply to the right.
Heart failure exacerbation [18][19][20][21]
Atrial fibrillation with RVR [22][23]
Acute mitral regurgitation [24]

Upper airway causes

Clinical features Diagnostic findings Acute management
Angioedema [25][26]
  • Swelling of the face, upper airway, body
  • Urticaria, hypotension, and/or bronchospasm
Foreign body aspiration [27]
Epiglottitis [28][29]
Deep neck infection [30]

Toxic-metabolic and other causes

Clinical features Diagnostic findings Acute management

Salicylate toxicity [31][32]

DKA [33][34]
CO toxicity [35][36]
  • Clinical diagnosis: history of exposure, typical symptoms, and COHb
  • CXR: usually normal
  • ABG: ↓ PaO2, ↑ Serum COHb (nonsmokers > 3–4%, smokers > 10%)
Anemia [37][38]
  • Normal or ↓ Hb

Anything that can cause metabolic acidosis (e.g., DKA, lactic acidosis, salicylate toxicity) can also cause acute dyspnea.

Differential diagnoses

System Differential Diagnoses [39][40][41][42]
Upper airway

The differential diagnoses listed here are not exhaustive.

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last updated 09/15/2020
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