NEEDLE EMC OF THE HUMAN DIAPHRAGM - POWER SPECTRAL-ANALYSIS IN NORMALSUBJECTS

Needle EMG of the diaphragm was performed in 43 diaphragms in 23 healt hy volunteers. The mean +/- standard deviation for the median frequenc y (MF) of the power spectrum was 233.3 +/- 58.1 Hz. The MF increased w ith age and showed a negative correlation with the forced vital capaci ty (FVC), but there was no correlation with other anthropometric measu res or the results of phrenic nerve conduction study. The higher MF in older subjects may be due to early recruitment of larger units. The n egative correlation between MF and FVC is likely secondary to a lower level of contraction required for normal breathing in subjects with hi gh FVC. The integrated EMG (iEMG) of each inspiration strongly correla ted with the tidal volume and the duration of inspiration. Power spect ral analysis of diaphragmatic EMG is feasible and reliable. It can be used to assess respiratory muscle fatigue and may help in the diagnosi s of neuromuscular disorders affecting the diaphragm. (C) 1996 John Wi ley & Sons, Inc.