Novel tailoring algorithm for abrupt motion artifact removal in photoplethysmogram signals

Photoplethysmogram (PPG) signals are widely used for wearable electronic devices nowadays. The PPG signal is extremely sensitive to the motion artifacts (MAs) caused by the subject's movement. The detection and removal of such MAs remains a difficult problem. Due to the complicated MA signal waveforms, none of the existing techniques can lead to satisfactory results. In this paper, a new framework to identify and tailor the abrupt MAs in PPG is proposed, which consists of feature extraction, change-point detection, and MA removal. In order to achieve the optimal performance, a data-dependent frame-size determination mechanism is employed. Experiments for the heart-beat-rate-measurement application have been conducted to demonstrate the effectiveness of our proposed method, by a correct detection rate of MAs at 98% and the average heart-beat-rate tracking accuracy above 97%. On the other hand, this new framework maintains the original signal temporal structure unlike the spectrum-based approach, and it can be further applied for the calculation of blood oxygen level (SpO₂).

Application of fingertip photoplethysmogram assessment of endothelial function in screening coronary heart disease patients / 吉林大学学报(医学版)

Objective:To investigate the application of photoplethysmogram in analyzing the fingertip pulse amplitude volume (PAV)to evaluate the endothelial function in diagnosing coronary heart disease,and to clarify its relationship with the risk factors of cardiovascular diseases.Methods:Total 409 patients with chest pain accepted coronary angiography (CAG)were selected and diveded into positive group (CAG+)(n=288)and negative group (CAG-) (n = 121)according to angiographic results.Fingertip photoplethysmogram was used to analyze the fingertip PAV by the way of applying endothelial function diagnostic after reactive ischemia,and the relationship between the PAV value and the risk factors of coronary heart diseases was analyzed,and the critical reference value of prediction index of coronary heart disease was determined.The risk factors such as age,gender,serum total cholesterol (TC ), low density lipoprotein (LDL ), high density lipoprotein (HDL ), non-HDL, serum triglyceride (TG),hypertension,diabetes,smoking,family history of coronary heart disease,body mass index (BMI)of the subjects in various groups were analyzed,and the relationship between the risk factors of coronary heart disease and PAV was analyzed by Logistic regression analysis.Results:The PAV of patients in CAG+group was significantly lower than that in CAG-group (P <0.01).The peak point of PAV was<1.37,if PAV<1.37 was used to predict the coronary heart disease,the predictive sensitivity,the specificity,the positive prediction and the negative prediction were 74.65%,44.63%, 76.24%, and 42.52%.The Logistic regression analysis showed that PAV was negatively associated with hypertension,smoking history,TG (OR= 1.476,OR=2.002, OR = 1.844;P < 0.01 ). Conclusion: PAV is associated with coronary heart disease and its risk factors (hypertension,smoking history,TG),and PAV=1.37 can be used as the peak point to predict the coronary heart disease.

Comparison of finger photoplethysmogram and cerebral state index for monitoring depth of anaesthesia / 实用医学杂志

Objective To explore the similarities and differences between finger photoplethysmogram (PPG) and CSI in monitoring the depth of anaesthesia in Chinese adults under general anaesthesia. Methods Ninety-three patients, ASA ⅠorⅡ, aged 20-67, under general anaesthesia were enrolled. Anaesthesia was induced with target-controlled infusion (TCI) of propofol. The initial TCI concentration of propofol was set at 0.5 mg·L-1 followed by increments of 0.5 mg·L-1 at 3-min interval until the score of Modified Observer's Assessment of Alertness/Sedation Scale (MOAAS)reached 0. PPG and CSI were continuously monitored and their values were recorded every 2-4 seconds. MOAAS was recorded every 30 seconds to evaluate the sedation level in the study period. ResultsFor the periodfrom pre-induction to pre-intubation, the difference of photoplethysmogram amplitudevalues had statistical significance between level 4 and level 3, level 3 and level 2 of MOAAS (P<0.05). CSIvalues declined along with the decrease of MOAAS levels and were statistically different between every two neighboring levels of MOAAS (P < 0.05). Photoplethysmogram amplitude (PPGA) and pulse beat interval (PBI) values showed significant differences before and after intubation, pre- and post-incision (P < 0.05). Conclusions PPGA and PBI appear to be suitable to monitor the nociceptive component of balanced general anesthesia , while the CSI exhibits a good performance in monitoring the sedation or hypnotic component of balanced general anesthesia , thusthe combination of PPGA and CSI would benefit the monitoring of the adequacy of depth of anaesthesia.

Factor Structure of Indices of the Second Derivative of the Finger Photoplethysmogram with Metabolic Components and Other Cardiovascular Risk Indicators

BACKGROUND: The second derivative of the finger photoplethysmogram (SDPTG) is an indicator of arterial stiffness. The present study was conducted to clarify the factor structure of indices of the SDPTG in combination with components of the metabolic syndrome (MetS), to elucidate the significance of the SDPTG among various cardiovascular risk factors. METHODS: The SDPTG was determined in the second forefinger of the left hand in 1,055 male workers (mean age, 44.2+/-6.4 years). Among 4 waves of SDPTG components, the ratios of the height of the "a" wave to that of the "b" and "d" waves were expressed as b/a and d/a, and used as SDPTG indices for the analysis. RESULTS: Principal axis factoring analysis was conducted using age, SDPTG indices, components of MetS, and the serum levels of C-reactive protein (CRP) and uric acid. Three factors were extracted, and the SDPTG indices were categorized in combination with age as the third factor. Metabolic components and the SDPTG indices were independently categorized. These three factors explained 44.4% of the total variation. Multiple logistic regression analysis revealed age, d/a, serum uric acid, serum CRP, and regular exercise as independent determinants of the risk of MetS. The odds ratios (95% confidence intervals) were 1.08 (1.04 to 1.11), 0.10 (0.01 to 0.73), 1.24 (1.06 to 1.44), 3.59 (2.37 to 5.42), and 0.48 (0.28 to 0.82), respectively. CONCLUSION: The SDPTG indices were categorized in combination with age, and they differed in characteristics from components of MetS or inflammatory markers. In addition, this cross-sectional study also revealed decrease of the d/a as a risk factor for the development of MetS.

Assessment of successful epidural steroid injection using photoplethysmogram

BACKGROUND:One of effective treatment methods for back pain and radiculopathy is epidural steroid injection (ESI). However, its effectiveness is hard to judge.So, it is strongly urged to develop a method to evaluate the proper injection of ESI. Photoplethysmogram (PPG) is known as a technique to measure blood oxygen saturation. We were intended to study the PPG for the evaluation of the ESI instantaneously. METHODS:All patients were explained for the study protocol to get informed consent.Twenty volunteers were recruited for this study and four of them were allocated in one of 5 ESI levels; L2-3, L3-4, L4-5, L5-S1 and caudal.They were in the lateral position with 4 PPG probes in their both 2nd fingers and 2nd toes.The PPG signals were collected to a device and converted digitally.PPG signal has two components, total absorbance (TA) and oscillating pulse component (OPC).We compared the both toe PPG signals before and after ESI based on the finger PPG. RESULTS:TA changed in 60% of ESI volunteers and L4-L5 and L5-S1 groups had high change rate compared to L2-L3 group.Also, the symptom relief rate of TA and OPC change volunteers of L4-L5 and L5-S1 were 100% but other level had variable relief rate. CONCLUSIONS:It is possible to use the PPG signal to predict ESI success based appropriate signal change.It is also needed to develop other level signal detection method and to modify appropriate guideline for the decision of change of PPG.

Development of a Wearable Pulse Transit Time Monitoring Device / 대한의료정보학회지

OBJECTIVES: We have developed a non.intrusive continuous PTT monitoring system, using a wearable device and wireless communication technology. METHODS: Pulse transit time (PTT) is a non.invasive measurement that shows promise in the continuous monitoring of blood pressure (BP) and the assessment of arterial stiffness. It has potential applications in wearable health monitoring devices. Generally, PTT is measured from the electrocardiogram (ECG) Rwave to a characteristic point on the peripheral pulse by photoplethysmography. However, for home healthcare applications, a system needs to be wearable and wireless. ECG and PPG were sampled at 1200 Hz and transmitted to a personal computer (PC) using Bluetooth communications. Heart rate (HR) and PTT were calculated by the PC from the signals received and waveforms of ECG, PPG, PTT and HR were displayed. RESULTS: In this study, we implemented a system that could be adapted to the wrist and measured ECG and a Photoplethysmogram (PPG). CONCLUSIONS: The wearable continuous PTT monitoring system developed in this study could be useful in home cardiovascular healthcare.

Estimation of Continuous Blood Pressure with Amplitude of Photoplethysmogram and Pulse Transit Time of Finger and Toe / 대한마취과학회지

BACKGROUND: The amplitude (AMP) of Photoplethysmogram (PPG) is used as a marker of vasodilatation. The pulse transit time (PTT), which shows a good correlation with blood pressure (BP), is not strong enough to detect the changes in BP. This study examined the sensitivity of the combined effect of the finger and toe AMP, and the PTT of PPG as a marker of the changes in BP during general anesthesia. METHODS: Forty patients receiving maxillofacial surgery under general anesthesia were enrolled in this study. During surgery, the intra-arterial BP, ECG, finger and toe PPG signals were measured. Using the R-wave from the ECG, the AMP and PTT was derived from PPG data. The correlation between BP and PPG parameters (AMP and PTT) were compared. New parameters that show high correlation with the BP were found. Regression equations for calculating the BP using the PPG parameters were formulated. RESULTS: The new parameter, log (fingerAMP/toeAMP), showed the highest correlation in each patient (mean correlation coefficient in the systolic BP: -0.846, diastolic BP: -0.858). However, when the data from all 40 patients were combined, the correlation coefficient of the toe PTT was highest (systolic BP: -0.726, diastolic BP: -0.646). The regression equation showed the highest correlation between the actual BP and calculated BP when the toe PTT and log (fingerAMP/toeAMP) were included. CONCLUSIONS: The AMP of the toe and finger PPG can be used to estimate the invasive continuous blood pressure.

THE CIRCULATION RESPONSE DURING CONTIONUOUS ISOMETRIC CONTRACTION ON TURNK MUSCLE / 体力科学

The purpose of this study was to investigate the circulation responses (heart rate (HR), systolic blood pressure (SBP) and second derivative of photoplethysmogram waveform index (|d/a|)) during 90 seconds continuous isometric contraction on trunk muscle. Subjects were 10 healthy male (22±1 years). Subjects performed 90 seconds continuous isometric contraction on Rectus Abdominus. Contraction intensity was 55.4±13.8% maximal voluntary contraction.HR and SBP were a significant increase after contraction beginning, immediately. |d/a| (one of the peripheral blood vessel contraction index) was a significant increase at 60 seconds after contraction beginning. After that, HR was an increase more, |d/a| showed a decline tendency. But, SBP was an increase more.The followings are suggestive by these results. When the contraction beginning, HR was increased immediately by central command, muscle mechano reflex and so on. The other hand, the peripheral blood vessel contraction was late by the accumulation of metabolism product from active muscle was late. When the prolong contraction time, the peripheral blood vessel was extension. But, SBP was increased more by increasing the cardio output, muscle tension and so on.

Impact of Kampo Therapy on the Second Derivative of the Photoplethysmogram (SDPTG) / 日本東洋医学雑誌

The effect of Kampo therapy (Japanese traditional herbal medicine) on the second derivative of the photoplethysmogram (SDPTG) was investigated. The SDPTG is the second derivative of the fingertip photoplethysmogram (PTG), which expresses the characteristics of the vascular system, the properties of peripheral vessels, and the state of blood flow. The subjects comprised 13 normal volunteers, 101 patients (21 males and 80 females; mean age 53±11 years) with 1 month of Kampo therapy, and 19 patients (4 males and 15 females; mean age 60±9 years) with 3 months of medication. Control subjects showed no significant changes in their vascular age after 1 month. Patients with a higher vascular age than expected before therapy showed improvement of their vascular age, after treatment for 1 month and 3 months. The difference between the vascular age and calendar age decreased from about 10 to 7 years after 1 month of therapy (n=65. p<0.001), and from about 9 to 4 years, after 3 months (n=11, p<0.01). Vascular age not only reflects organic vessel wall sclerosis due to arteriosclerosis, but also a vascular wall tone that is closely related to the autonomic nervous system. The change of vascular age within a relatively short period suggested a functional change rather than an organic change of the vessels.

Effect of alcohol intake on microvascular and EEG responses to cold water stimulation. .DELTA.DPG and EEG power spectral analysis / 体力科学

In this study, we examined changes in the amplitude of differential digital photoplethysmogram (ΔDPG) and the power spectral changes of EEG at rest during cold water immersion of the contralateral fingers (2°C), and after alcohol intake (0.3 g/kg) in 8 male subjects. This experiment showed that the ΔDPG amplitude decreased at rest and finger blood pressure was increased during the cold water stimulation, but there was no signifincant change in heart rate and EEG power spectrum. On chronological measurements for 30 minutes after alcohol intake, ΔDPG amplitude decreased slightly and finger blood pressure increased. Heart rate also tended to increase, and the alpha 1 power (8.0-9.8 Hz) on EEG gradually increased. The ODPG and finger blood pressure responses to cold water stimulation every 10 minutes was decreased after alcohol intake, whereas heart rate was not affected. However, a decrease in the alphal power after stimulation was revealed. From these results, it may be concluded that during 5-10 s of cold water stimulation, increased skin sympathetic nerve activity was one of the factors that raises blood pressure.