Technique of on-line analysis of diaphragmatic electromyogram activity in the newborn.

The present study provides an on-line analysis of diaphragmatic electromyographic activity (EMGdi) in newborns. EMGdi was recorded using surface electrodes. EMGdi signals were processed using a microcomputer (Apple IIe). The centroid frequency (Fc) and the high over low (H/L) frequencies ratio of the power spectrum were calculated. Furthermore the model frequency (Fo) was computed by an autoregressive model of the EMG signal. EMGdi analysis was performed in seven healthy spontaneously breathing preterm newborns. Fc ranged from 46-62 Hz. Fc was significantly lower than Fo in four of the seven preterm newborns. The coefficient of variation for Fc was significantly lower than for the H/L ratio (p less than 0.001). The coefficients of variation for Fo and Fc were not significantly different, but the percentage of rejected calculations for Fo was significantly higher than for Fc (p less than 0.01). Therefore, in healthy preterm newborns, Fc appears to be the best index of EMGdi analysis.