CRACKCast E025 – Dyspnea

In CRACKCast, Podcast by Adam Thomas3 Comments

This episode of CRACKCast covers Rosen’s Chapter 25, Dyspnea. Dyspnea has a broad differential; to list them all would leave you short of breath. This episode covers an approach to dyspnea and the critical diagnoses to remember for this cardinal presentation.

Shownotes – PDF Here


Rosen’s in Perspective

“Dyspnea”: uncomfortable sensation of breathlessness, “Air hunger”

  • Non-specific spectrum from mild disease to severe disease
  • May be referred to as different terms

Other terms to know:

Tachypnea − RR > normal >45-60 bpm in neonates; to >18 bpm in adults

Hyperpnea – Greater than normal minute ventilation to meet metabolic requirements

Hyperventilation – Minute ventilation exceeding metabolic demand

-> ABG showing normal PaO2

+ Uncompensated respiratory alkalosis

+ Elevated pH

Dyspnea on Exertion (DOE) – Dyspnea provoked by physical effort

Orthopnea – Dyspnea in a recumbent position

Paroxysmal Nocturnal Dyspnea (PND) – Sudden SOB at night


  • Normal breathing controlled by:
    • Centrally by the respiratory centres in the medulla oblongata
    • Peripherally by the chemoreceptors in the carotid bodies
    • Mechanical centres in the diaphragm and skeletal muscles
  • Any imbalance in these sites leads to dyspnea – mechanism not fully understood

Perception of dyspnea relates to:

  • Increased lung resistance
    • COPD or Asthma
  • Increased respiratory drive
    • Severe hypoxemia, acidosis, centrally acting toxins, or CNS events
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1) List 10 critical causes of dyspnea

First key question:

  • Is the dyspnea cardio-pulmonary OR toxic-metabolic?



  1. Airway obstruction
    a) Heimlich maneuver & direct laryngoscopy with McGill forceps
  2. Pulmonary embolism
  3. Non-cardiogenic pulmonary edema
  4. Anaphylaxis
  5. Respiratory failure
  6. Tension pneumothorax +/- flail chest
    a) Severe respiratory distress, hypoxia, hypotension
    b) Decreased breath sounds, oxygen desaturation


  1. Pulmonary edema (due to CHF)
  2. Myocardial infarction
  3. Cardiac tamponade


  1. Toxic ingestions (e.g. organophosphate ingestion)
  2. DKA
  3. Epiglottitis
  4. CO poisoning
  5. Acute chest syndrome (e.g. Sickle cell)

CVA / intracranial catastrophe




1) Outline your approach to the acutely dyspneic patient

Management and disposition

  • Dyspnea requires simultaneous evaluation and management
    • Use the MOVIE approach and initiate empiric treatments based on:
      • Trauma
      • Anaphylaxis
      • Foreign body
      • Infectious causes
      • Cardiac causes (dysrhythmia, ischemic, CHF)
      • PE
      • Asthma / COPD

Signs & Ancillary Studies

Full set of vitals, patient’s general appearance, skin/nail findings

  • Neck, lung, chest, cardiac, extremities and neuro exam can assist with diagnosis
  • Tests to consider:
    • Vitals with SPO2 however know when it is unreliable
    • ABG
    • ECG
    • Beside U/S
    • CXR
    • Labs – rule out anemia, infection, electrolyte abnormalities, or renal failure
  • WBC is of little sensitivity or specificity
  • BNP, troponin, and D-dimer may be of some use
    • Soft tissue lateral neck – for upper airway processes
    • CT chest for intra-thoracic causes (PE, pneumonia, etc.)

2) Name at least 6 uncommon causes of dyspnea

  • Valvular heart disease
  • Cardiomyopathy
  • Mechanical interference (pregnancy, ascites, obesity, hiatal hernia)
  • Ruptured diaphragm
  • Thyrotoxicosis
  • Guillain-Barre syndrome
  • Tick paralysis
  • MS
  • ALS
  • Polymyositis
  • Porphyria

This episode was edited and uploaded by Colin Sedgwick (@colin_sedgwick)

Adam Thomas

CRACKCast Co-founder and newly minted FRCPC emergency physician from the University of British Columbia. Currently spending his days between a fellowship in critical care and making sure his toddler survives past age 5.
Chris Lipp is one of the founding Fathers for CrackCast. He currently divides his time as an EM Physician in Calgary (SHC/FMC) and in Sports Medicine (Innovative Sport Medicine Calgary). His interests are in paediatrics, endurance sports, exercise as medicine, and wilderness medical education. When he isn’t outdoors with his family, he's brewing a coffee or dreaming up an adventure…..