Combined ultrasonographic and neurographic examination: a new technique to evaluate phrenic nerve function

In this report a new technique for simultaneous assessment of the electrical and mechanical properties of the diaphragm is presented. The phrenic nerve of 9 healthy persons was stimulated at the neck using magnetic stimulation. Electrical activity was recorded using chest surface electrodes. The mechanical function of the diaphragm was evaluated by performing combined B- and M-mode ultrasonographic examination. The data show that this method helps to distinguish the diaphragm muscle compound action potential from electrical activity derived from neighboring muscles activated by the brachial plexus. Furthermore, it provides a non-invasive tool which can easily be used in clinical practice to study the mechanical properties of the diaphragm.