A real-time rule-based method of stenosis evaluation for arteriovenous fistula care by multiple sites blood flow measurement

Arteriovenous fistula (AVF) care is crucial for hemodialysis patients. Neglecting the care of patients on strict AVF care may cause stenosis and affect hemodialysis efficiency. Hence, AVF has been called a lifeline for these patients. Currently, in clinical care, angiography and ultrasound are used to evaluate the degree of stenosis (DOS) in AVF. However, these tools are expensive, time-consuming, and inappropriate for quick assessments before dialysis therapy or even at home care. This study proposed a real-time rule-based method of stenosis evaluation for AVF care by measuring the blood flow of multiple sites with Doppler ultrasound. The features of blood flow analyzed were the average flow rate (AFR) and the ratio of flow variation (RFV), which were measured in the fistula and arteriovenous anastomosis sites, respectively. In the clinical examinations of 60 patients, the results indicated that AFR would gradually decrease with DOS, and RFV reached the maximum at 30% to 50% stenosis and the lowest at 30%; this difference was statistically significant (p<0.05). Moreover, the classification results indicated that the proposed method achieved a high classification rate of 95% as well as a shorter processing time within 10 ms. This study also compared the results from a phantom experiment, which had three different DOS simulated vessel classes, and it showed the same trend. The proposed method was considered to be potentially suitable for real-time program design with a microsystem in wearable or small monitoring devices so as to provide a simple and fast rapid screening method for clinical AVF care.