Phrenic nerve conduction in infancy and early childhood

Diaphragmatic action potentials (DAPs) were mapped on the thorax bilaterall y in 16 neurologically normal infants and 8 boys aged 1 to 4 years during a rtificial ventilation after thoracic surgery. Transcutaneous stimulation wa s used to activate the phrenic nerve at the supraclavicular fossa at the en d of an artificial inspiration. The DAPs were of positive polarity and were recorded on the ipsilateral anterolateral chest wall over the sixth to the eighth intercostal spaces, with a maximal peak at the seventh intercostal space. The DAP latencies gradually decreased from 6 to 8 ms at birth to abo ut 5 ms at the age of 1 year, despite an increase of conduction distance. S tatistical analyses revealed that DAP amplitude did not correlate with age. The latencies and amplitudes of the DAPs displayed little interside variat ion. The results are valuable not only as a reference for the diagnosis of patients with phrenic nerve palsy, but also as an indicator of the normal d evelopment of the phrenic nerve. (C) 2000 John Wiley & Sons, Inc.