Experimental research on the electromagnetic radiation immunity of a kind of portable monitor / 中国医疗器械杂志

The paper is focused on a kind of portable monitor that is widely used in military hospitals. In order to study the electromagnetic radiation immunity of the monitor, the experiments of electromagnetic radiation caused by radio frequency continuous wave in reverberation chamber and by ultra wide band (UWB) electromagnetic pulse have been done. The study results show that UWB electromagnetic pulse interferes observably the operating state of the monitor. It should be paid high attention to take protective measures. The monitor tested has some electromagnetic immunity ability for radio frequency continuous wave radiation. The frequent abnormal phenomena are baseline drift and waveform distortion. The electromagnetic sensitivity of the monitor is related to the frequency of interference source. The monitor tested is most sensitive to the frequency of 390 MHz.

A new method based on down-sampling for QRS complexes detection / 生物医学工程学杂志

This paper presented a new method based on down-sampling for QRS complexes detection for the reason that ECG's frequency components mostly centralize 0.05-35 Hz. Firstly, the original ECG signals were down-sampled. Secondly, self adapting and self study theory were used to select the amplitude threshold and slope threshold for R-wave detection. At the same time, the refractory idiosyncrasy of heart was taken into account to reduce the misdetection. Thirdly, back-trace technique was used to reduce undetected error. Finally, the corresponding R-wave position was up-dated in the original ECG signals. The performance of the method was tested by MIT/BIH ECG database and the clinical data were collected from the affiliated hospital of Chongqing Medical University. The detection rate of 98% was achieved. Experimental results indicated that the method was simple, effective, accurate and unaffected on sample rate.

Dynamic analysis of heart rate variability based on wavelet transform / 生物医学工程学杂志

The analysis of heart rate variability (HRV) has become a tool for noninvasively detecting the cardiovascular modulation of autonomic nervous system. Traditional analysis in frequency domain mainly includes calculating the power and detecting the peak frequency of each physiological frequency band. Whether employing the classical method or AR model to estimate the spectrum, the approximate stationarity of HRV is presupposed. Only in short term analysis can data meet this condition, while in long term the nonstationarity of HRV notably appears. A dynamic analysis method based on wavelet transform was proposed in this paper, which not only can obtain the traditional indices in frequency domain, but can compute their dynamic values varying with time, called short-time power and short-time LF/HF ratio. The latter can dynamically evaluate the activity of autonomic nervous. Finally the method was applied to trace the balance of autonomic nervous in Atropin drag experiment.