The respiratory assessment of a 44-year-old female patient diagnosed with myasthenia gravis shows: vital capacity 475 mL, maximum inspiratory pressure (MIP) ?18 cm H2O

The patient is 5 feet 6 inches tall and weighs 188 lb. The most recent ABG on a 2 L/min nasal cannula is pH 7.32, PaCO2 49 mm Hg, PaO2 77 mm Hg, SaO2 95%, HCO3? 24 mEq/L. The most appropriate recommendation for this patient is which of the following?
a. 50% air entrainment mask
b. Continuous positive airway pressure
c. Noninvasive positive pressure ventilation
d. Intubation and mechanical ventilation

ANS: D
The arterial blood gas result for this patient shows an acute respiratory acidosis. That along with a vital capacity of 7.4 mL/kg and the maximum inspiratory pressure (MIP) of −18 cm H2O point to the fact that this patient is also showing signs of muscle weakness that is progressively worsen-ing. This requires prompt intubation and support to prevent acute respiratory failure. The 50% air entrainment mask and the continuous positive airway pressure (CPAP) will not provide support for this patient's ventilatory problems. Noninvasive positive pressure ventilation (NPPV) is not appropriate for this patient because of the patient's decreasing muscle strength.