Muller N, Volgyesi G, Bryan M H, Bryan A C
J Pediatr. 1979 Nov;95(5 Pt 1):793-7. doi: 10.1016/s0022-3476(79)80738-6.
We have previously demonstrated that diaphragmatic muscle fatigue can be diagnosed in infants from spectral frequency analysis of the surface diaphragmatic electromyogram. This requires a digital computer, but the analysis takes several days. Spectral frequency changes, however, can be accurately reflected by band pass filtering and expressing the ratio of high-frequency power to low-frequency power. A fall in this ratio of greater than 20% indicates muscle fatigue. Using a simple analog device to obtain this ratio permits the results to be immediately available; we have used this method to study weaning from mechanical ventilators in ten infants. With a successful weaning step there is no significant change in the ratio, whereas an unsuccessful weaning step invariably leads to a decrease in the ratio of greater than 20%, which precedes CO2 retention and clinical deterioration. These data indicate that diaphragmatic muscle fatigue plays an important role in the infant's response to lung disease. Monitoring of the high/low frequency ratio may be helpful in weaning infants from assisted ventilation.
