When is pulmonary function testing indicated in the evaluation of myasthenia gravis?

Updated: Sep 20, 2018
  • Author: William D Goldenberg, MD; Chief Editor: Andrew K Chang, MD, MS  more...
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Patients with respiratory distress should have an evaluation of pulmonary function, providing that the patient is not in obvious respiratory failure. This evaluation includes pulse oximetry, a measure of pulmonary function (ie, peak expiratory flow, forced expiratory volume in 1 second [FEV1]), and arterial blood gas (ABG) sampling to determine partial pressure of carbon dioxide (PCO2). [9] A negative inspiratory force (NIF) of 30 cm H2O or less or a forced vital capacity (FVC) of 20ml/Kg are indicative of a myathenic crisis and airway compromise. [6]

Evidence of hypoxemia, poor respiratory effort, or CO2 retention is an indication for intubation and mechanical ventilation. [9]

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