Photoplethysmography is an important optical method in healthcare and contains a wealth of information about physiological dynamics. For a quantitative assessment of vascular tone indices, an effective and modern method of analyzing the relief of the photoplethysmogram within the pulse cycle is required. A new method for detecting singular points of the contour of photoplethysmograms is proposed, based on the model of a multilayer perceptron neural network (MLPNN). The successful work of the network of the method for finding the systolic peak, dicrotic notch and diastolic peak has been demonstrated. It is shown that the average relative error does not exceed 5 percent. The proposed method can be used in computer monitoring systems for vascular tone.
The paper presents the results of a harmonic analysis of the indicators of photoplethysmograms of the human index finger, which characterize the pulse blood filling and tone of large diameter arteries (blood distribution vessels), as well as indicators of the tone of small diameter arteries. Fourier analysis of periodic changes in the tone of regional arteries of various diameters was carried out with natural breathing, in a test with deep breathing (hyperventilation), with the voluntary breathing at three fixed frequencies (0.2Hz, 0.1Hz; 0.05Hz). The tests were performed under spirographic control. The advantage of the spectral analysis of photoplethysmographic indicators over the traditional harmonic analysis of PPG in studies of the relationship between changes in the tone of regional arteries of various diameters on the one hand, and the depth and frequency of breathing of the subject on the other hand is shown. Spectral analysis of photoplethysmographic indicators is more effective in observing the dynamics of transient changes in the tone of regional arteries in people with neurocirculatory disorders of blood circulation regulation.
Long-term continuous registration of photoplethysmograms allows observing periodic fluctuations of regional vascular tone, which is important for non-invasive functional diagnostics of a number of diseases of the vascular system. But the relief of the photoplethysmogram within the pulse cycle in some functional states is poorly expressed, which significantly reduces the possibility of a quantitative assessment of the indicators of vascular tone. We propose a new algorithm for detecting special points of the contour of photoplethysmograms, based on the discovered relationship between the position of these special points and the duration of the pulse cycle. The efficiency of the new algorithm in cases where there is no diastolic rise has been demonstrated. It is shown that the average relative error does not exceed 5%. The proposed algorithm can be used in computer monitoring systems for vascular tone.
A new method of photoplethysmogram analysis for complex assessment of natural fluctuations of pulse blood filling and tone of peripheral arteries based on the results of long-term photoplethysmographic monitoring of peripheral volumetric pulse is proposed. The method is based on finding the variational, statistical and spectral indicators of the relative amplitude characteristics of the photoplethysmogram. Standard algorithms of variational, statistical and spectral analysis are used to realize the method. The method can be used for the analysis of disorders of regulation of regional vascular pulse blood filling, tone arteries of small diameter, as well as conditions of regional venous return of blood to the heart.
The most promising method for the quantitative determination of cardiovascular tone indicators and of cerebral hemodynamics indicators is the method of impedance plethysmography. The accurate determination of these indicators requires the correct identification of the characteristic points in the thoracic impedance plethysmogram and the cranial impedance plethysmogram respectively. An algorithm for automatic analysis of these plethysmogram is presented. The algorithm is based on the hard temporal relationships between the phases of the cardiac cycle and the characteristic points of the plethysmogram. The proposed algorithm does not require estimation of initial data and selection of processing parameters. Use of the method on healthy subjects showed a very low detection error of characteristic points.
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