Phrenic nerve pacing in infants and children: A review of experience and report on the usefulness of phrenic nerve stimulation studies

Nine infants and children, referred for phrenic nerve pacemakers, had measurements of phrenic nerve conduction times and diaphragmatic action potential amplitudes. In these pediatric patients, phrenic nerve conduction times varied from 2.7 to 7.8 msec, were quite reproducible, and were shorter than phrenic nerve conduction times in adults; phrenic nerve conduction time increased with age and with increasing distance between the stimulating electrode and the diaphragm. Diaphragmatic action potential amplitudes varied from 0.08 to 4.1 mV, roughly equivalent to amplitudes in adults, but were variable between patients and within patients on different days. Lower amplitudes were obtained after percutaneous stimulation than after direct phrenic nerve stimulation. Five patients underwent preoperative, percutaneous phrenic nerve stimulation. Strong diaphragmatic contractions allowed us to advise for pacemaker insertion in three patients; weak or absent diaphragmatic contractions allowed us to advise against pacemaker insertion in two patients. Postoperatively, noninvasive measurements of oxygen, carbon dioxide, tidal volume, and diaphragmatic action potential amplitudes have been used to adjust the phrenic nerve pacemaker settings. Phrenic nerve pacemakers have facilitated discharge from the hospital to a home-based ventilation program in six of the seven patients in whom they were inserted. We conclude that phrenic nerve pacing is a practical method of supporting ventilation in carefully selected infants and children. Phrenic nerve stimulation studies are useful in selecting patients for pacing and in adjusting the pacemaker settings.