1217 A Complex Case of Progressive Hypercarbic Respiratory Failure

Abstract Introduction Progressive hypercarbic respiratory failure in the absence of overt intrinsic lung disease, thoracic cage abnormalities, CNS depressants, or neuromuscular disease poses a unique diagnostic challenge. Furthermore, continued respiratory failure in patients compliant with non-invasive ventilation warrants additional evaluation for alternative diagnoses. We present a case which produced a unique diagnostic challenge to the inpatient sleep medicine service. Report of case(s) A 46 year-old female with a past medical history significant for T2DM, COVID pneumonia, and seizures presented for acute on chronic hypercarbic respiratory failure in the setting of left hemi-diaphragm paralysis. She experienced multiple (greater than ten) hospitalizations requiring intubation for hypercarbic respiratory failure. Initial work up revealed negative inspiratory force of -40 cm H20. Pulmonary function tests revealed a restrictive pattern with FEV1/FVC of 70%. CT Chest revealed no parenchymal abnormalities. Admission ABG of 7.30/56. She was started on non-invasive ventilation through average volume assured pressure support mode with goal volumes of eight cc/kg. Despite effective ventilatory support with excellent compliance she had increasing requirements leading to near twenty-four hours of total use. Repeat hospitalization occurred for respiratory failure and new left arm weakness which raised concern for underlying neuromuscular disease as etiology. MuSK antibodies were sent and resulted positive at a titer of 1.35nmol/L, consistent with a diagnosis of Myasthenia gravis. The patient was treated with prednisone, plasma exchange, and rituximab with marked improvement in clinical and respiratory status. The patient was successfully weaned down to nocturnal use of non-invasive ventilation with preserved eucarbia. Conclusion Myasthenia gravis can lead to marked respiratory muscle weakness and respiratory failure. Common triggers of crisis include infection, medications, electrolyte abnormalities, and thyroid disease. Up to twenty percent of patients present with myasthenic crisis as their initial symptoms. Continued evaluation of forced vital capacity, and negative inspiratory force are important measures to follow for signs of disease progression. This case proved difficult in the setting of recurrent admissions believed to be secondary to hemidiaphragm paralysis and previous COVID infection. It is imperative to maintain a broad differential in working up respiratory failure and consider myasthenia in the proper clinical context. Support (if any)