1238 West Nile Encephalitis with suspected diaphragmatic dysfunction leading to sleep apnea with associated hypoventilation

Abstract

Currently, there are no guidelines on the management of acute sleep disordered breathing in the ICU or inpatient setting. Here, we report a case in which an acute sleep medicine evaluation was utilized to treat a patient with West Nile Encephalitis and sleep related hypoventilation with suspected diaphragmatic weakness. This is an 82 yo male who presented with lethargy and dyspnea after a recent trip to El Salvador. Physical exam was significant for shallow, rapid respirations with mild use of accessory muscles and fluctuating mental status. Patient denied any history of lung disease or OSA but became progressively more somnolent with rising pCO2 levels. This prompted a sleep medicine consult to optimize PAP therapy as patient had declined elective intubation. Due to patient’s unstable condition, a bedside trial was performed in the Step Down Unit utilizing BIPAP with settings of 18/8 cmH20, PS 4 cmh20 and 2L O2. Results showed an AHI of 72 with evidence of worsening hypoventilation based on his pCO2 of 80 (ABG). However, this study was limited due to the inability to differentiate central from obstructive events given the available equipment. Concurrently, further workup for encephalopathy revealed presence of West Nile Encephalitis based on positive IgM antibodies in CSF. Upon review of additional studies, chest imaging was concerning for diaphragmatic dysfunction. This concern was corroborated by ultrasonography which, although of poor image quality, failed to show any significant inspiratory contraction of the R diaphragm. A repeat BIPAP trial was then performed utilizing a backup rate of 12 bpm with pressure of 16/10 cmH20 and 2L O2. Results showed an AHI of 15.7 with average O2 91.6%. In the days following, his pCO2 levels improved to 50. In conclusion, WNV-induced myositis vs phrenic neuropathy leads the differential for this patient’s diaphragmatic dysfunction/hypoventilation. Further testing is needed.