A novel compliance-pressure loop approach to quantify arterial compliance in systole and in diastole

摘要

Arterial compliance has been recognized as a critical parameter in governing pulsatile flow dynamics. It has traditionally been assumed constant throughout the cardiac cycle and its computation has been based either on the classic Windkessel model (C) in diastole or the stroke volume over pulse pressure (Cv) method in systole. Other methods using area (Cam) or two-area (Ctam) and exponential (C(P)exp1) methods were used for the cardiac cycle. We proposed a novel compliance-pressure loop (CPP loop) approach for the quantification of arterial compliance and compared it to existing linear and nonlinear methods. Experimental data were gathered in 5 dogs and blood pressure levels were varied (systolic pressure of 100?mmHg–185?mmHg) with induced hypertension and vasodilation. Results showed the limited regime of validity of C (Control:0.4681?±?0.1270?ml/mmHg, MTX:0.3015?±?0.1264?ml/mmHg and NTP:1.8323?±?0.7207?ml/mmHg) and Cv(Control:0.3583?±?0.0158?ml/mmHg, MTX:0.2602?±?0.1275?ml/mmHg and NTP:0.4131?±?0.0589?ml/mmHg), Cam(Control:0.4175?±?0.0505, MTX:0.3086?±?0.1568 and NTP:1.4181?±?0.4812) and Ctam(Control: 0.2064?±?0.0228?ml/mmHg, MTX:0.1967?±?0.0884?ml/mmHg, NTP:0.0881?±?0.0375?ml/mmHg) and that C(P)exp1underestimates the arterial compliance compared to our method (Control:0.2233?±?0.0168?ml/mmHg vs 0.4481?±?0.0515?ml/mmHg, MTX:0.1976?±?0.0964?ml/mmHg vs 0.3273?±?0.1443?ml/mmHg and NTP: 0.2177?±?0.0273?ml/mmHg vs 1.9990?±?1.8221?ml/mmHg at mean arterial pressure). The CPP method based on the exponential method is superior, as it provides continuous compliance variations and CPP loop area can be readily visualized from hypotension to hypertension conditions. We conclude that the concept of using compliance-pressure loop is advantageous as it can afford continuous and accurate tracking of the dynamic arterial behavior despite greatly varying blood pressure levels.