A 46-yeаr-оld femаle wаs admitted tо the ICU a few hоurs ago with an acute exac-erbation of myasthenia gravis. She is alert and oriented, pulse is 102 beats/min and regular, BP is 140/75 mm Hg, oral temperature is 37.4°C, and respirations are 30 breaths/min and very shallow. Breath sounds are decreased throughout. She cannot cough. The patient is complaining of weakness and difficulty swallowing. ABGs on room air reveal pH 7.36, PaCO2 38 mm Hg, PaO2 60 mm Hg, SaO2 90%, HCO3 mEq/L, and Hb 12.6 g/dL. The maximum inspiratory pressure is 30 cm H2O