Abstract
In the present paper, a simple QRS detection algorithm is proposed aiming at applications of QRS intervals and its variations to evaluate mental state. The pre-processing part of the proposed algorithm is a digital filter which has only three coefficients but has the characteristics of notch filter for the powerline interference and the bandpass filter for QRS frequency content. The decision rule is a simple one using two thresholds. The noise sensitivities were measured for a gold standard ECG; synthesized ECG corrupted with five different types of synthesized noise, which was introduced by Friesen et al. (1990). The performance of the proposed algorithm was compared with Engelese's algorithm which showed the best performance in the Friesen's study. Both algorithms made no false positive nor false negative for ECG corrupted with 50Hz powerline interference and with simulated baseline drift due to respiration. The proposed algorithm had more tolerance to abrupt baseline shift than the latter. Two algorithms had almost same performance for EMG corrupted noise. The proposed algorithm was tested using actual ECG measured under various mental and physical task conditions, which showed errors less than 0.12%. It is concluded that the proposed QRS detection algorithm has a good ability considering its memory and calculation load.
