Myasthenia gravis is an autoimmune disease characterized by failure of neuromuscular transmission due to antibodies blocking postsynaptic nicotinic acetylcholine receptors. The resulting weakness may affect respiratory and bulbar musculature. Ineffective respiratory muscle strength results in small tidal volumes, with resulting atelectasis and hypercarbia. Weakness of bulbar muscles reduces cough and swallow effectiveness and thus reduces the ability to handle secretions. The combined weakness of respiratory and bulbar muscles predisposes patients to pulmonary and upper-airway infections.

Several methods of pulmonary conditioning can help improve pulmonary function by helping to clear mucus, reduce atelectasis, and prevent lung infections in intensive care unit (ICU) patients. Some of the options available include incentive spirometry (IS), chest physiotherapy with postural drainage, manual cough assist, percussion therapy, mechanical insufflation/exsufflation/intermittent positive pressure (IPPV) ventilation and intrapulmonary percussive ventilation (IPV). Incentive spirometry involves taking a maximal inspiration through a monitoring device to promote lung expansion and prevent atelectasis. IPPV is a patient-controlled, pneumatic, oscillating-pressure breathing device that loosens mucus by internally percussing the airway with high-frequency gas bursts. The patient can trigger the device by pressing a button during inspiration and releasing the button during expiration. Flutter-valve therapy is similar to IPPV in that oscillations of pressure are transmitted throughout the tracheobronchial tree to help loosen secretions, except that oscillations occur during expiration.