Assessment of diaphragm paralysis with oesophageal electromyography and unilateral magnetic phrenic nerve stimulation

The purpose of this study was to establish a sensitive and reliable method of diagnosing diaphragm paralysis by recording the diaphragm compound muscl e action potential (CMAP) using a multipair oesophageal electrode and unila teral magnetic phrenic nerve stimulation. An oesophageal electrode catheter was designed containing six coils (1 cm w ide and 3 cm apart), creating an array of four sequential electrode pairs. The oesophageal catheter was taped at the nose with the proximal electrode pair 40 cm from the nares, Eight patients with unilateral (n=5) or bilatera l (n=3) diaphragm paralysis were studied, Five to seven phrenic nerve stimu lations were performed at 80% of maximum magnetic stimulator output and the CMAPs were recorded simultaneously from the four pairs of electrodes, In the five patients with unilateral diaphragm paralysis, the CMAP amplitud es and latencies were 1.16+/-0.29 mV and 7.6+/-1.5 ms for functioning sides . No diaphragm CMAP could be detected when stimulating nonfunctioning phren ic nerves. This study shows that diaphragm paralysis can be reliably diagnosed by unil ateral magnetic stimulation combined with a multipaired oesophageal electro de.