values of pressure given flow and R, C, L parameters, or find values of R, C, L given flow and pressure. An example for the two-element model is shown below, where I(t) is depicted as an input signal during systole and diastole. Systole is represented by the sin function, while flow during diastole is zero. s represents the duration of the cardiac cycle, while Ts represents the duration of systole, and Td represents the duration of diastole (e.g. in seconds). In physiology and disease The 'Windkessel effect' becomes diminished with age as the elastic arteries become less compliant, termed hardening of the arteries or arteriosclerosis, probably secondary to fragmentation and loss of elastin. The reduction in the Windkessel effect results in increased pulse pressure for a given stroke volume. The increased pulse pressure results in elevated systolic pressure (hypertension) which increases the risk of myocardial infarction, stroke, heart failure and a variety of other cardiovascular diseases. Limitations Although the Windkessel is a simple and convenient concept, it has been largely superseded by more modern approaches that interpret arterial pressure and flow waveforms in terms of wave propagation and reflection. Recent attempts to integrate wave propagation and Windkessel approaches through a reservoir concept, have been criticized and a recent consensus document highlighted the wave-like nature of the reservoir. See also References Cardiovascular physiology Cardiology hr:Zračna boca hu:Légüst