Advanced Practice: Respiratory Failure in Myasthenia Gravis Crisis


  • As many as 20% of patients with myasthenia gravis experience crisis
  • Crisis can be initial manifestation of disease
  • Respiratory failure is feared complication

Clinical Presentation of Respiratory Failure in MG Patient

  • Increasing weakness (bulbar/proximal extremity/neck)
  • Dyspnea usually worse in supine position (increased dependence of diaphragm on gravity)
  • Important to remember that patients may not exhibit normal signs of respiratory failure secondary to weakness (ex: accessory muscle use)


  • medication noncompliance
  • infection
  • surgery
  • pregnancy/child birth
  • drugs (antibiotics, cardiovascular, anesthetics, anticonvulsants, antipsychotics, etc.)


  • Most Important Step = Assessment/Monitoring of Respiratory Function
  • Vital Capacity (VC) and Max Inspiratory Pressure (aka Negative Inspiratory Force) are most important to monitor during crisis
    • Consider intubation if VC below 15-20 ml/kg OR MIP/NIF less negative than -25 to -30 cmH2O
  • Often need ICU for frequent monitoring, q2-4 hr respiratory function testing
  • Plasma Exchange OR IVIG (rapid acting therapies)
  • Glucocorticoids: crisis patients often started on high dose steroids
    • Associated with transient worsening of weakness, however less of a concern with concurrent plasma exchange/IVIG
  • Stay tuned next week for intubation pearls!


Bird S, Levine J. “Myasthenic Crisis.” UpToDate. 25 August 2016;

Tintinalli, JE. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 8th ed. NewYork, NY: McGraw-Hill Education LLC, 2016.