A Rapid assessment method on fistula stenosis staging for hemodialysis patients

The AV access is usually evaluated by feeling thrill and pulsation through palpation, listening for the bruit by using a stethoscope, Doppler ultrasound imaging, or angiography, etc. However, these techniques require specific equipment and operator. Phonoangiography is a noninvasive tool for identifying vascular diameter change. In this study, a mock model has been set up to simplify the simulation of blood flow condition. Phonographic signal is recorded by electronic stethoscope and further signal processed. The relationship of phonographic signals and stenotic lesions is studied. Early detection of hemodialysis access problems such as stenosis and thrombosis is very important issue. The purpose of this study is to develop a phonographic system to evaluate arteriovenous shunt (AVS) stenosis of hemodialysis patients. The degree of stenosis (DOS) is used as an index to classify the AV access condition, and is determined by the narrowing percentage of normal vessels. In this mock model, the DOS is set to be varied from 0, 50, 70, 80, 85, 90, 92.5 to 95%. The empirical mode decomposition (EMD) method is applied to analyze the relationship between DOS and spectrogram. Verification is based on Doppler ultrasound which is the golden standard in clinical application. From the experimental results, the proposed method is demonstrated to be feasible for charactering the staging of DOS conditions. There is a great correlation between the phonoangiography and the severity of DOS in AV access. This noninvasive method may be useful and potential for early detection in home-care use.