외부 압력에 대한 혈관 팽창 특성을 활용한 커프리스 동맥압 추정에 관한 연구 (A study on cuffless arterial blood pressure estimation by utilizing arterial distensibility against external pressure)

In this study, we aim to investigate the correlation between changes in arterial blood pressure and the Photoplethysmography (PPG) signal, which is one of the most commonly utilized physiological signals, alongside electrocardiography (ECG) signals. We will use the PPG signal, which reflects changes in blood flow due to external pressure, in conjunction with ECG to examine the variations in arterial blood pressure. Similar to oscillometric methods, during the gradual increment and decrement of external pressure, the PPG signal is influenced by the external pressure, leading to turbulence in the blood vessels. Consequently, vascular dilation occurs, and changes in vascular volume due to this dilation are estimated through PPG. The portion where turbulence occurs during the increase in external pressure is defined as the first turbulence onset region, while the region where turbulence occurs as external pressure decreases is termed the second turbulence onset region. To examine changes in the PPG waveform, inflection points expected to be due to turbulence were detected in the envelope formed by connecting the peaks of the PPG signal. In the first turbulence onset region, where turbulence is induced by an increase in external pressure, a high correlation was observed with systolic blood pressure. In the second turbulence onset region, where turbulence occurs as external pressure decreases, a high correlation was found with diastolic blood pressure. To identify inflection points in the envelopes formed by connecting the peaks of the PPG signal measured during the turbulence onset regions, we investigated the correlation with systolic and diastolic blood pressure by varying the interpolation method and adjusting the window size of the smoothing filter. When examining the correlation with diastolic blood pressure in the second turbulence onset region, it was visually discernible that the amplitude changes in the PPG signal, and certain inflection points showed a very high correlation with blood pressure. This resulted in minimal errors and a narrow range in the estimated diastolic blood pressure. When a shorter window length(100 samples) is used for the smoothing filter, an average RMSE error was approximately 4.6812±5.73 mmHg / 2.7722± 3.59 mmHg (SYS/DIA) were observed. This level of accuracy is comparable to commercially available at-home blood pressure measurement devices (including cuffs), which have an accuracy of ±5mmHg. The method proposed in this study involved the application of a smoothing filter with an appropriate window size and utilized the correlation between inflection points and turbulence onset regions to estimate arterial blood pressure. It demonstrated a higher accuracy in estimating diastolic blood pressure compared to systolic blood pressure. When complemented with the PTT (Pulse Transit Time)-based systolic blood pressure estimation method known for its high accuracy, it holds the potential for estimating blood pressure, potentially replacing wearable devices or home blood pressure monitors in the future. Although the study was conducted with a small number of participants, it exhibited significant similarities, and while the arterial pressure estimation based on turbulence induced by external pressure is not yet conclusive, the resemblance to blood pressure in response to the proposed idea appears promising. Therefore, it was confirmed that further research is needed to validate its effectiveness in the future.

In this study, we aim to investigate the correlation between changes in arterial blood pressure and the Photoplethysmography (PPG) signal, which is one of the most commonly utilized physiological signals, alongside electrocardiography (ECG) signals. We will use the PPG signal, which reflects changes in blood flow due to external pressure, in conjunction with ECG to examine the variations in arterial blood pressure. Similar to oscillometric methods, during the gradual increment and decrement of external pressure, the PPG signal is influenced by the external pressure, leading to turbulence in the blood vessels. Consequently, vascular dilation occurs, and changes in vascular volume due to this dilation are estimated through PPG. The portion where turbulence occurs during the increase in external pressure is defined as the first turbulence onset region, while the region where turbulence occurs as external pressure decreases is termed the second turbulence onset region. To examine changes in the PPG waveform, inflection points expected to be due to turbulence were detected in the envelope formed by connecting the peaks of the PPG signal. In the first turbulence onset region, where turbulence is induced by an increase in external pressure, a high correlation was observed with systolic blood pressure. In the second turbulence onset region, where turbulence occurs as external pressure decreases, a high correlation was found with diastolic blood pressure. To identify inflection points in the envelopes formed by connecting the peaks of the PPG signal measured during the turbulence onset regions, we investigated the correlation with systolic and diastolic blood pressure by varying the interpolation method and adjusting the window size of the smoothing filter. When examining the correlation with diastolic blood pressure in the second turbulence onset region, it was visually discernible that the amplitude changes in the PPG signal, and certain inflection points showed a very high correlation with blood pressure. This resulted in minimal errors and a narrow range in the estimated diastolic blood pressure. When a shorter window length(100 samples) is used for the smoothing filter, an average RMSE error was approximately 4.6812±5.73 mmHg / 2.7722± 3.59 mmHg (SYS/DIA) were observed. This level of accuracy is comparable to commercially available at-home blood pressure measurement devices (including cuffs), which have an accuracy of ±5mmHg. The method proposed in this study involved the application of a smoothing filter with an appropriate window size and utilized the correlation between inflection points and turbulence onset regions to estimate arterial blood pressure. It demonstrated a higher accuracy in estimating diastolic blood pressure compared to systolic blood pressure. When complemented with the PTT (Pulse Transit Time)-based systolic blood pressure estimation method known for its high accuracy, it holds the potential for estimating blood pressure, potentially replacing wearable devices or home blood pressure monitors in the future. Although the study was conducted with a small number of participants, it exhibited significant similarities, and while the arterial pressure estimation based on turbulence induced by external pressure is not yet conclusive, the resemblance to blood pressure in response to the proposed idea appears promising. Therefore, it was confirmed that further research is needed to validate its effectiveness in the future.