Esophageal versus surface recording of diaphragm compound muscle action potential.

Abstract

Repeated diaphragm compound muscle action potential (CMAP) recordings may help to understand the pathophysiology of respiratory muscle weakness. Neurally adjusted ventilator assist (NAVA) uses esophageal EMG electrodes to drive the ventilator. We evaluated the feasibility of CMAP recordings using these electrodes and established normal values. Bilateral cervical phrenic nerve electrical stimulation was performed in 15 healthy volunteers. CMAP recordings with esophageal NAVA electrodes were compared with surface electrode recordings during inspiratory and expiratory pause. Compared with surface recordings, esophageal CMAP amplitudes were higher with increased latencies. Differences between the 2 techniques were most prominent in inspiration. For both recording techniques, amplitudes were higher, and latencies were longer during inspiration. Latencies were also longer when measured on the left side. Diaphragm CMAPs can be measured using the commercially available esophageal NAVA probe. This may facilitate repeated diaphragm CMAP studies in mechanically ventilated patients.