Differential Diagnosis

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  • Common causes of undiagnosed dyspnea in pulmonary clinics
    • Asthma - 32%
    • Unknown - 15%
    • Psychogenic - 9%
    • Deconditioning - 7%
    • Cardiac, upper airway, ILD, COPD - each 6%

  • Other causes to consider
    • Occupational asthma, RADS
    • VCD
    • Hyperventilation syndrome (panic attacks) - breathing pattern is usually slow and deep
    • Exercise-induced hyperventilation - usually considered psychogenic
    • Exercise hyperventilation and mitochondrial myopathy
      • Occurs in 8.5% with difficult to diagnose dyspnea; elevated ventilatory response and heart-rate response to exercise may be diagnosed as psychogenic or deconditioning
    • Functional or "sighing" dyspnea - episodic sense of inability to fully expand lungs, "sighing” pattern of respiration during episode, occurs at rest, often relieved by exercise or other distraction, usually not provoked by stress or anxiety, benign and often improves with reassurance
    • Bilateral diaphragmatic weakness - causes orthopnea, hypoinflated CXR
    • Unilateral diaphragmatic weakness - often starts as viral syndrome and neck/shoulder pains, with onset of exertional dyspnea days to weeks later, CXR with elevated hemidiaphragm, self-limited in 75%
    • Methemoglobinemia - functional anemia, with pulse ox ~88% and discrepancy with saturation on ABG, chocolate brown arterial blood, most commonly associated with dapsone, primaquine, 20% benzocaine, surgery/anesthesia, dehydration (pediatric)
    • Platypnea-orthodeoxia - striking clinical syndrome characterized by dyspnea and deoxygenation accompanying a change from recumbent to a sitting or standing position
      • Platypnea without orthodeoxia - associated with dysautonomia, orthostatic hypotension
    • Clopidogrel (Plavix) and ticagrelor (Brillinta)-associated dyspnea - no change in pulmonary/cardiac function noted
    • Pulmonary vascular disease
    • Metabolic acidosis
    • Obesity

Diagnostic Approach (Peters)

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