Thursday, April 23, 15:30 - 18:00, Location: Show and Tell Area B
Hsien-Tsai Wu, Chun-Ho Lee, Tsang-Chin Wu, An-Bang Li
Myocardial infarction, stroke, hypertension, etc. are common modern diseases, people try to avoid these leading killers and those who are affected by these diseases cause heavy load to their families. Many people wonder why and how these diseases affect our bodies. According to many studies, arterial stiffness is the main reason that causes these diseases, and atherosclerosis begins with the oxidation of Low Density Cholesterols in the blood inflames the vessel wall. At the early stage of atherosclerosis, plaques are formed inside the vessel, and when these plaques rupture or fester, the platelet will coagulate the damage area, this eventually lead to thrombus or blood clot. Minor thrombus causes unstable angina. Large thrombus will cause diseases such as Myocardial infarction, stroke, and other coronary diseases.
How to effectively predict atherosclerosis related diseases become a principal task. Therefore, frequently monitor the level of arterial stiffness not only assists to understand one’s personal coronary condition, also facilitates leading one’s living style and diet to the better aspect, and thus stays away from these deadly atherosclerosis diseases.
We will show a system 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 the stimulation to the blood vessels, and uses this index to reflect the function of endothelium cell, therefore, early self-monitoring of cardiovascular dysfunction and arterial stiffness can be easily and effectively achieved. In homecare area, only few minutes is needed for self arterial stiffness assessment. Therefore, early self-monitoring of cardio-vascular dys-function and arterial stiffness is easily and effectively achieved.
In hardware part, there are radius/upper arm air pressure sensing device, analog processing unit, radius/upper arm air pump motor unit, mixed signal processing unit, peripheral unit, and memory unit. Radial arteries will be under a stable pressure, air pressure sensing device will extract the radial pulse waveform, at this time, the pulse waveform is small and distorted, which includes skin noise effect from cuff and external power supply’s noise. Analog signal processing unit will convert the pulse wave into DC and filtering out the noises then amplifies it, purified analog signal will be convert into digital by mixed signal processing unit(MSP430F449) with sampling rate at 200Hz. Then digital data is transmit to PC’s analyzing software via UART(RS-232) , the analyzing software will plot the pulse waveform on the screen then analyze it. The memory unit is used for storing the pulse waveform data, external peripheral devices are keyboard and LCD for real-time pulse waveform displaying.
Software part is responsible for receiving the digital data from mixed signal processing unit, then use pulse waveform analyzing algorithm to calculated the vasodilatation index and measuring data storage.The analyzing software executes every 5 seconds, after receiving the data from mixed signal processing unit, which sampling rate is 200Hz, or 5 ms. The received date will be normalized to make analysis simpler. The peak, valley of waveform will be found, then Riemann Sum to calculate the area under the curve of waveform.
After the discussions in above, this study developed a method for assessing endothelial function in radial artery, it irritates upper arm endothelium cell to release NO by cuff inflation, and the blood flow will increase after the vasodilatation caused by the diffusion of NO into the smooth muscle layer, then using the calculation of area under the curve of pulse wave form to reflect the change of blood flow, the blood flow change before and after the inflation can then derive the vasodilatation index. This vasodilatation index can reflect the health of endothelium cell, and can be used as a reference for early detection of atherosclerosis. This study has proven that air pressure sensing system has good reproducibility and reliability through series of human experiments. In future, the proposed system will perform large scale experiment of the clinical application on human body, with static analyzing method, search for the relationship between hyperemia vasodilatation and atherosclerosis related diseases.