Chun-Ho Lee

Arterial Stiffness Using Radial Arterial Waveforms Measured at the Wrist as an Indicator of Diabetic Control in the Elderly

Although current technique of photoplethysmography (PPG) is a popular noninvasive method of waveform contour analysis in assessing arterial stiffness, data obtained are frequently affected by various environmental and physiological factors. We proposed an easily operable air pressure sensing system (APSS) for radial arterial signal capturing. Totally, 108 subjects (young, the aged with or without diabetes) were recruited from July 2009 to May 2010. Arterial waveform signals from the wrist were obtained and analyzed using Hilbert-Huang transformation (HHT). Through ensemble empirical mode decomposition (EEMD), the signals were decomposed into eight intrinsic mode functions (IMF1-8) of which IMF5 was found to be the desired signal with a discernible diastolic peak. The results showed significant differences in reflection index (RI) and stiffness index (SI) from the young subjects and those from the aged participants with or without diabetes. Significant differences in RI and SI were also noted between subjects with well-controlled diabetes and those without. Good reproducibility and correlation were demonstrated. In conclusion, the present study proposed the application of radial arterial signal capturing subsystem and HHT in acquiring more reliable data on RI and SI compared with the conventional PPG method.

Assessment of Endothelial Function Using Arterial Pressure Signals

Peripheral arterial tonometry (PAT) is a useful method to assess endothelial function. Analysis of pulse wave amplitude with PAT during reactive hyperemia can be used to study peripheral vascular endothelial function very well. We had injected a specific nitric oxide (NO) synthesize inhibitor intra-arterially into five adult male rats to verify the validation of our proposed photoplethysmograpy (PPG) system for endothelial function assessment. However, the reproducibility was not good for the system applied for measuring fingertip peripheral arteries. Therefore, an air-pressure sensing system with the high reproducibility was developed for peripheral vascular endothelial function assessment. This study showed that the vasodilatation index measured with air-pressure sensing system correlated very well with that measured using peripheral arterial tonometry. In addition, only few minutes are needed for conducting a self endothelial function assessment at home. And, early self-monitoring of cardiovascular dysfunction and arterial stiffness can be easily and effectively achieved.

Arterial Waveforms Measured at the Wrist as Indicators of Diabetic Endothelial Dysfunction in the Elderly

Although air pressure sensing system (APSS) is a reliable means of assessing vascular endothelial function with high reproducibility, it cannot distinguish between the effects of age and diabetes. This paper aimed at investigating the potential benefit of utilizing signal-processing technique in improving the clinical validity of APSS. Arterial waveforms acquired from the left wrist before and after induction of reactive hyperemia over the left arm were recorded using APSS. Values of dilatation index (DI) were calculated and compared before (DIORIGINAL) and after (DIEEMD) ensemble empirical mode decomposition (EEMD). Compared with DIORIGINAL, DIEEMD showed better negative correlations with anthropometric, hemodynamic, and biochemical parameters (all P <; 0.05). Instead of DIORIGINAL, DIEEMD significantly distinguished between the two groups of testing subjects (P = 0.008). EEMD further refined the validity of DI obtained through APSS, which is a simple self-operable system in evaluating endothelial function for the general public. It may also serve as an assessment tool for clinicians to implement timely therapeutic measures for diabetic patients.

A Simplified Approach to Assessing Penile Endothelial Function in Young Individuals at Risk of Erectile Dysfunction

Erectile dysfunction (ED) reflects a risk for systemic cardiovascular diseases by virtue of a common etiology of vascular endothelial dysfunction, which is increasingly reported to affect young adults. On the basis of physiological phenomenon of reactive hyperemia (RH), systemic and penile endothelial functions in healthy young adults were compared with the use of digital data on arterial waveforms before and after RH induction. Between July 2009 and March 2011, 32 young adult volunteers with normal erectile functions were recruited. Questionnaires on medical histories and sexual functions and blood samples for testosterone and biochemical analyses were obtained. Dilatation index (DI) and penile arterial waveform amplitude (PAWA) ratios for assessing systemic and penile endothelial function were acquired with an air pressure sensing system on the arm and a penile arterial waveform analyzing system on the penis, respectively. A total cholesterol/high-density lipoprotein (TC/HDL) ratio greater than 4.1 was used to define high risk for ED. Remarkable positive correlation was noted between DI and PAWA ratio (r = .640, P < .001). DI showed significant positive associations with serum testosterone (P = .012) and serum HDL level, whereas it showed negative correlations with total triglyceride and glycosylated hemoglobulin levels, body weight, waist circumference, body mass index, and diastolic blood pressure. Similarly, the PAWA ratio showed significant positive correlations with serum testosterone (P < .001) and HDL levels, but negative associations with body weight, waist circumference, and body mass index. Both DI and PAWA ratio successfully identified participants at high risk for ED (eg, TC/HDL ratio > 4.1; P < .05). Our results demonstrated that penile endothelial function can be assessed by evaluating systemic endothelial function in young healthy adults for early identification of risk for ED.

Penile Arterial Waveform Analyzing System for Early Identification of Young Adults with High Risk of Erectile Dysfunction

INTRODUCTION High prevalence of erectile dysfunction in young adults has raised much concern regarding early identification of risk factors for timely intervention. AIM This study aimed at identifying young males at risk through a novel penile arterial waveform analyzing system. METHODS Between July 2009 and December 2010, 30 young adult volunteers of age 18 to 29 without known history of vascular diseases or erectile dysfunction were recruited. MAIN OUTCOME MEASURES Basic demographic and anthropometric characteristics (i.e., age, body weight, body height, body mass index, waist circumference) were recorded. Blood samples were obtained for determining levels of testosterone, glycosylated hemoglobin, triglyceride, fasting sugar, low- and high-density lipoproteins (HDL). Data obtained from visual sexual stimulation (VSS) RigiScan and the penile arterial waveform amplitude (PAWA) ratios were compared in terms of their correlations with anthropometric and serum biochemical parameters using Pearsons correlation analysis. RESULTS PAWA ratios were found to correlate with Rigidity (tip and base) (r = 0.425, P = 0.019 and r = 0.664, P < 0.001, respectively). Significant associations of PAWA ratios were noted not only with serum testosterone level but also with risk factors for metabolic and cardiovascular diseases including total triglyceride, HDL, age, waist circumference, body mass index, and diastolic blood pressure. However, VSS RigiScan failed in identifying significant correlations with HDL, age, and diastolic blood pressure. CONCLUSIONS Not only could the penile waveform analyzing system assess penile endothelial function in young adults, but the results also showed significant associations with their serum testosterone levels and metabolic parameters. The findings suggest that PAWA ratio may serve as an indicator for early identification and treatment of young adults at risk of erectile dysfunction.

Endothelium function assessment with radial pulse wave signals

This study proposes a method of measuring vasodilatation via air pressure sensing to assess the function of endothelium cells. The vasodilatation index is calculated according to the change of area of waveform caused by stimulation to the blood vessels, and uses this index to reflect the function of endothelium cells; therefore, early self-monitoring of cardiovascular dysfunction and arterial stiffness can be easily and effectively achieved. Only a few minutes are needed for conducting a self endothelial function assessment. Furthermore, this study improves the high cost pressure sensors used in Reactive Hyperemia Peripheral Arterial Tonometry (RH-PAT) and its inconveniences. 30 test subjects with no previous cardiovascular disease record were included for testing the reproducibility of the instrument. It has been proven that the air pressure sensing method proposed in this study has higher reproducibility and practicality than the Photoplethysmography (PPG) system for assessing the function of endothelium cells.

Digital Pulse Volume Based Endothelial Function Detector for Early Stage Formation of Atherosclerosis

In this paper, we discuss the development of an easy-to-use non-intrusive endothelial function assessment instrument. The instrument records the digital pulse volume (DPV) from the fingers. We studied 42 subjects (28 men and 14 women, 22 to 64 years of age) and showed the good performance of self-developed system for monitoring endothelial function. The system is capable to apply both area under the curve of DPV and traditional amplitude methods for endothelial function assessment. Both methods are highly correlated as well as able to reflect the changes of blood flow volume in reactive hyperemia. At home, only a few minutes are needed for conducting a self endothelial function assessment. Therefore, early self-monitoring of cardiovascular dysfunction and arterial stiffness can be easily and effectively achieved.

Linguistic analysis of the arterial pressure signals using frequency and rank order statistics

We introduce a quantitative metric to define distances among symbolic sequences. In application to the amplitude time series of arterial pressure signals, this approach provides new quantitative information that is not measured by conventional heart rate variability techniques. Complex physiologic signals may carry unique dynamical signatures that are related to their underlying mechanisms. We present a method based on rank order statistics of symbolic sequences to investigate the profile of different types of physiologic dynamics. We apply this method to amplitude of arterial pressure signals fluctuations. The method robustly discriminates patterns generated from healthy and pathologic states, as well as aging.

Multiscale entropy indicates vascular abnormalities in the aged

This study investigates the feasibility and sensitivity of a novel multiscale entropy index (MEI) in detecting subtle endothelial dysfunction in young and middle-aged subjects. Between December 2009 and May 2010, totally 70 subjects were recruited from a hospital, and categorized into young group (Group 1), middle-aged or elderly group (Group 2). Arterial pulse wave signals were acquired from the wrist with air pressure sensing system (APSS), followed by MEI and dilatation index (DI) analyses. In conclusion, a reduction in multiscale entropy reflected age related vascular changes and may serve as a more sensitive indicator of subtle endothelial dysfunction compared with DI in the setting of aged.

Predicting arterial stiffness with the aid of ensemble empirical mode decomposition(EEMD) algorithm

In this study, we propose an easy-to-use non-invasive arterial stiffness assessment instrument that can be used to record the radial arterial pressure signals from the wrist. The system combines the ensemble empirical mode decomposition (EEMD) algorithm with the signals to derive a modified reflection index (MRI). The performance of MRI was verified based on 42 subjects (33 men and 9 women, 20 to 27 years of age). Early self-monitoring of cardiovascular dysfunction and arterial stiffness can be easily and effectively achieved by MRI because only few minutes are needed for conducting at home.