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Weaning from the ventilator using bipap in myasthenia gravis

Weaning from mechanical ventilation is frequently difficult in patients recovering from a myasthenia gravis (MG) crisis.4 Typically, such patients are initially treated with high levels of pressure support ventilation. This ventilatory mode delivers positive pressure at the onset of each inspiration triggered by the patient’s effort. During weaning, these levels of pressure support are gradually reduced. Then, before extubation, patients are connected to a Tpiece (an external tube that allows oxygen delivery through the endotracheal tube) to assess their ventilatory capacity without mechanical support. Often, patients with MG are easily weaned to low levels of pressure support only to reach a standstill. Insufficient respiratory muscle strength may cause these patients to repeatedly fail these T-piece trials and extubation attempts. However, prolonged endotracheal intubation increases the risk of airway damage and ventilator-associated pneumonia.1 Noninvasive bilevel positive airway pressure (BiPAP) ventilation delivers adjustable degrees of positive pressure throughout the respiratory cycle to overcome upper airway resistance during inspiration and prevent alveolar collapse at the end of expiration.2 Pressures are delivered through a close-fitting mask, thus avoiding the need for an endotracheal tube. Because it reduces the work of breathing, BiPAP may be an ideal method of gradual weaning for patients with MG who develop ventilator-dependency. We report our experience using BiPAP as a weaning method in five episodes of respiratory failure occurring in three patients with an exacerbation of MG. The patients were mechanically ventilated due to neuromuscular respiratory failure caused by MG crisis. None had alternative explanations for respiratory failure. All patients had failed repeated T-piece trials and were receiving low levels of pressure support ventilation (inspiratory pressure 10 mm Hg and end-expiratory pressures 8 mm Hg) at the time of extubation and institution of BiPAP support. All had been treated with plasmapheresis in the acute phase and received incremental dosages of pyridostigmine during the weaning process, with improved muscle strength documented by serial neurological examinations. Timing of extubation and institution of BiPAP was based on the clinical judgment of the treating physician. Bedside respiratory function tests and arterial blood gases were not consistently measured before extubation. BiPAP ventilation was well tolerated and prevented reintubation in all cases. Before institution of BiPAP, patients had been intubated for a mean time of 13 days (range, 2–26 days). BiPAP inspiratory pressures ranged from 18 to 8 mm Hg and expiratory pressures from 8 to 4 mm Hg. No cases of pneumonia occurred despite all patients having bulbar weakness. Several days of BiPAP ventilation were needed in most cases (Table 1). Prior experience with BiPAP has largely been in patients with underlying pulmonary disease or with chronic neuromuscular disorders. BiPAP may prevent intubation in selected patients with MG, but its value in weaning from the ventilator has not been previously investigated.3 Weaning trials are subjective and dependent on many factors, mostly physician preferences. However, we found BiPAP use may facilitate weaning and shorten the time that pa-