Electromyogram processing for sleep research.

A computer method for quantifying the submental electromyographic surface interference pattern (EMG) during sleep and wakefulness by amplitude envelope measurement for consecutive 2-sec intervals is described. The method is largely insensitive to electrocardiogram (EKG) artifact. Though this algorithm was developed as part of a program to detect electroencephalographic (EEG), electrooculographic (EOG), tonic and phasic EMG changes during sleep, the method is applicable by itself wherever the envelope width of the EMG interference pattern is of interest. The results obtained correlate well with visual estimates of the amplitude envelope of the raw EMG. It offers increased speed, accuracy and reproducibility compared to visual EMG evaluation and enables a high degree of information extraction. The simplicity of the algorithm permits implementation and on-line processing on a small laboratory computer.