The fatigue of the diaphragm was determined with electromyography ir.35 patients with chronic obstructive emphysema (COPD) and in 47 nomaJ subjects serving as the control.It was found that the high/low frequency ratio (H/L) and the central frequency (Fc) of the diaphragmatic electromyogiam (EMGdi) were markedly decreased after diaphragmatic fatigue in COPD patients as well as in the controls ( P