Heart Rate Variability Detecting Research Based On Potoplethysmography Pulse Wave

Heart rate variability (HRV) refers to small variations in the human heart beatcycle, which usually refers to small fluctuations of the R wave between successiveheartbeat. Studies have shown that the higher nervous activities of the brain,spontaneous rhythmic activity of the central nervous system and other factorsmodulate the cardiac autonomic nervous system and leads to the generation of HRV.The HRV signal contains a lot of information about the cardiovascular system nervousand humoral regulation, detection of heart rate variability in patients can give a lot ofinformation about the state of the autonomic nervous system balance. Proposing andstudy of HRV is an important breakthrough and achievement in the history of modernmedicine, especially for the early diagnosis of cardiovascular diseases and otherrelated diseases, treatment and prognosis, HRV analysis has shown its potentialclinical the and its value is compelling. It has been recognized by recent studies thatthe application of heart rate variability to non-invasively, quantitatively analyze thefunctional status of the autonomic nervous is reasonable. Current decete method ofHRV is to get ECG signal by ECG machine, and then record the ECG cycle, thismethod is expensive and complicated to operate, it is difficult to detect repeatedly, soit is not suitable for families guardianship. This paper presents a simple, non-invasive,effective and safe and reliable family guardianship HRV detector, so that users candetecte HRV signal at home Conveniently.This paper focuses on the acquisition of heart rate variability fromphotoplethysmography pulse wave and the main contents and results are as follows.Pulse wave generation and propagation mechanism, and the characteristics of thepulse wave were researched, a variety of analytical methods on pulse wave wereresearched--time domain analysis, frequency domain analysis and time-frequencyanalysis. Time domain analysis method, is earliest used clinically, but this methodcannot fully reflect characteristics of the pulse signal. Frequency domain analysismethod can get more information which is more accurate than the time-domainanalysis, however, this method is based on the assumption that the signal beinganalyzed is stationary signals, it does not adequately reflect change of the spectralstructure of the pulse signal over time. Time-frequency analysis method can describethe spectral components of each moment. This paper selected wavelet analysismethod to process and analyze the pulse wave.This paper designed hardware circuit of the photoplethysmography, using thephotoelectric sensor to obtain blood volume pulse wave, and converted it intoelectrical signals by integrated circuit OPT101, and then sent it through the low-pass filter circuit, the limit wave circuit and rejecter circuit for filtering and amplifying，then the processed signal is sent into MCU for further processing.This paper researched the wavelet analysis method, and chose the bior wavelet todeal with the baseline drift, frequency interference, the EMG interference noise ofpulse wave signal. Chose the cubic spline wavelet to decompose the pulse wave signal,selected the corresponding the level for reconstruction, and drew the energy valuecurve, then used the threshold method to identify the P-wave peak point of the pulsewave, the pulse wave starting point A, and finally calculated the pulse wave cycle.The system has been tested, on the use of this method to extract the HRV signaland the ECG to extract the HRV signal were performed time domain method andfrequency domain method to analyze and compare the results of their results, themethod the paper described to obtain HRV signal is reasonable and feasibility.