Pulmonary function tests and blood gases in worsening myasthenia gravis.

The aim of this study was to determine whether pulmonary function tests have a role in predicting the need for ventilation support in myasthenia gravis. Medical records were reviewed for 42 patients with severe myasthenia gravis who required 55 admissions to the intensive care unit. Patients with a vital capacity of more than 20 ml/kg, a maximal expiratory pressure more than 40 cm H(2)O, or a maximal inspiratory pressure more negative than -40 cm H(2)O are unlikely to require mechanical ventilation. A decline of 30% or more in maximal inspiratory pressure predicted a group at higher risk of requiring mechanical or noninvasive ventilation. Hypercapnia was frequent and was more common in patients who required mechanical ventilation. Worsening of these pulmonary function and blood gas values in patients with myasthenia gravis may guide decisions about intubation and ventilatory support.