Last updated: September 6, 2022

Summarytoggle arrow icon

Dyspnea, or shortness of breath, is a subjective feeling of breathing discomfort. It 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, medication use), upper airway (e.g., epiglottitis, foreign body aspiration), psychological, and neuromuscular pathologies. On initial presentation, it is important to immediately evaluate the patient for any urgent or life-threatening causes of dyspnea using patient history, physical examination, and diagnostic testing. Once immediately life-threatening causes have been ruled out, a more detailed patient history should be obtained and further testing performed to narrow the differential diagnosis.

See also “Respiratory failure and arrest.”

Initial managementtoggle arrow icon

Approach [1][2][3]

Assume that all dyspnea is life-threatening until proven otherwise and perform the following steps concurrently, not sequentially.

Prioritize rapid identification and treatment of critical causes of dyspnea over advanced testing to obtain a definitive diagnosis. [4]

When evaluating a patient with dyspnea, always consider infection control and the need for PPE and patient isolation.

Red flags in dyspnea

The presence of any of these red flags suggests that dyspnea is the result of a serious pathologic process.

Anticipate rapid clinical deterioration in patients with red flag features.

Immediately life-threatening causes of dyspnea

See also “Rapidly reversible causes of respiratory failure.”

The severity of symptoms reported by the patient may not correlate with disease severity. Remain vigilant for life-threatening causes of dyspnea. [2]

Diagnosticstoggle arrow icon

The diagnostic evaluation of undifferentiated dyspnea aims to first rule out immediately life-threatening causes of dyspnea and then determine the etiology, guided by the pretest probability of the diagnoses under consideration.

Initial evaluation [2][5][6]

Applicable to most patients with undifferentiated dyspnea

Additional evaluation

Guided by clinical assessment and pretest probability

Pulmonary causestoggle arrow icon

Clinical features Diagnostic findings Acute management
Pneumonia [10]
COPD exacerbation (AECOPD) [11][12]
Asthma exacerbation [13]
Tension pneumothorax [15][16]
Spontaneous pneumothorax [15][17][18]
  • Sudden, sharp unilateral chest pain
  • Acute dyspnea
  • Hypoxemia
  • Hyperresonance, decreased breath sounds on affected side
  • Crepitus
  • History of lung disease or trauma
Pulmonary embolism [19]
Fat embolism [20]
Acute chest syndrome [22][23]
ARDS [24][25]

Cardiac causestoggle arrow icon

Clinical features Diagnostic findings Acute management
Acute coronary syndrome [26][27]
Cardiac tamponade [28]
  • 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 [29][30][31][32]
Hypertrophic cardiomyopathy [33][34]
Atrial fibrillation with RVR [35][36]
Acute mitral regurgitation [37]

Upper airway causestoggle arrow icon

Clinical features Diagnostic findings Acute management
Anaphylaxis [2][38][39]
Angioedema [40][41]
Foreign body aspiration [42]
Epiglottitis [43][44]
Deep neck infection [45]

Toxic-metabolic and other causestoggle arrow icon

Clinical features Diagnostic findings Acute management

Salicylate toxicity [46][47]

Organophosphate poisoning [2][48]
DKA [49][50]
Carbon monoxide poisoning [51][52]
Anemia [53][54]
  • Normal or ↓ Hb

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

Overview of causes of dyspnea by speed of onsettoggle arrow icon

Causes of dyspnea by speed of onset [1][2][55][56][57]
System Sudden onset Acute onset Chronic onset
Upper airway
  • N/A

Cardiopulmonary disease may be mistaken for panic attacks, as symptoms and pathogenesis overlap. Consider organic causes before attributing dyspnea to anxiety. [2][60]

Referencestoggle arrow icon

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