The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

DIAGNOSING DIAPHRAGMATIC DYSFUNCTION WITH CONTINUOUS DIAPHRAGMATIC MUSCLE ACTIVITY MONITORING

Daniel D. Rowley1, Frank J. Caruso1, Stuart Lowson2, Jürgen Witte2,3; 1Pulmonary Diagnostics & Respiratory Therapy Services, University of Virginia Medical Center, Charlottesville, VA; 2Anesthesiology & Intensive Care Medicine, University of Virginia Health System, Charlottesville, VA; 3Anesthesiology & Intensive Care Medicine, University of Münster, Münster, Germany

BACKGROUND: Pulmonary complications after liver transplantation (LTX) are common and lead to increased morbidity and mortality. Although right phrenic nerve injury is regarded as common after LTX, it is difficult to diagnose objectively at the bedside. Neurally adjusted ventilator assistance (NAVA) is a new mode of mechanical ventilation (MV) that uses a special esophagogastric tube with embedded electrodes to detect diaphragm myofiber electrical activity (Edi) during contraction. As part of an ongoing assessment of Edi monitoring and NAVA mode, we identified and diagnosed three cases of diaphragmatic paralysis post-OLTX. METHOD: Adult patients were identified who were spontaneously breathing but not ready for extubation because of a failed spontaneous breathing trial (SBT). Flow trigger sensitivity of 2 is standard. Communication between the Edi catheter and ventilator was established with a cable-module connection. The Edi catheter was inserted via the nasal route. Correct placement was verified with a disposable CO2 detector and by visualizing ECG waveform color changes on the ventilator’s monitor when Edi signals occurred. Airway and Edi scalar waveforms was then recorded. Transthoracic ultrasound was performed to assess diaphragm muscular activity when an Edi signal of less than 2 mV was displayed on the ventilator’s monitor. RESULTS: Three patients were identified who failed to remain extubated after passing a 30-minute CPAP SBT. Evidence of accessory muscle flexion during inspiratory efforts was present in each patient, and no Edi-signals were detected during patient initiated breaths. Bedside transthoracic ultrasound revealed ascites and diaphragmatic paralysis; unilateral in one case and bilateral in two. CONCLUSION: Our findings reveal that patients may pneumatically trigger assisted breaths during MV despite having markedly suppressed, or absent, diaphragm myofiber electrical activity. Flexion of accessory muscles may explain why pneumatic breath triggering occurs when Edi signals are suppressed or absent. This could further explain the failed extubation attempts in this patient population. Our observations demonstrate that diaphragmatic dysfunction during MV may be grossly under appreciated by using standard assessment techniques. Aside from NAVA mode, the Edi catheter may be used as a clinical adjunct to evaluate diaphragm function objectively at the bedside. Sponsored Research - None