Mean value of pulse pressure: The key feature in ambulatory arterial stiffness index estimation using regression models

Objective: Ambulatory arterial stiffness index (AASI) is an index which indicates arterial stiffness. This work aims to explore the mathematical relationship between AASI and mean value of PP (PP), and reveal the importance of PP during AASI estimating. Meanwhile, a well-performing AASI estimation model is presented.Methods: To evaluate AASI, electrocardiograph (ECG) signal, photoplethysmogram (PPG) signal and arterial blood pressure (ABP) are used as the source of AASI estimation. Features are extracted from the above three signals. Meanwhile, fitting curve analysis and regression models are implemented to describe the relationship between AASI and PP.Results: Among three fitting curves on AASI and PP, cubic polynomial curve performs best. The introduction of feature PP in AASI estimation reduced LR's MAE from 0.0556 to 0.0372, SVMR's MAE from 0.0413 to 0.0343 and RFR's MAE from 0.0386 to 0.0256. All three estimation models obtain considerable improvement, especially on the previous worst-performing linear regression.Significance: This work presents the mathematical association between AASI and PP. AASI estimation using regression models can be significantly improved by involving PP as its key feature, which is not only meaningful for exploring the connection between vascular elasticity function and pulse pressure, but also hold importance for the diagnosis of cardiovascular arteriosclerosis and atherosclerosis at the early stage.