Key result
Circuit models suggest back pressure is more useful than pulsatility index for resistive vascular beds.
Why the study?
The interpretation of pulsatility index in feeder arteries to low-impedance vascular beds is unclear and may benefit from a new modeling approach.
A theoretical electrical circuit model suggests that back pressure P(z) may be a more useful characterizing parameter than pulsatility index for vascular beds where impedance is largely resistive.
Model favors back pressure over pulsatility index in resistive beds; hypothesis-generating and requires clinical validation before practice change.
A simple electrical circuit is proposed as a model for peripheral vascular beds of low impedance. The model consists of a flow and pressure source, i.e. the 'feeder' artery, with the vascular bed represented by a Zener diode Z giving rise to a 'back pressure' P(z) and a pure resistance R. By applying Ohm's law to the definition of pulsatility index PI(flow) of flow in the feeder artery, it is shown that PI(flow) is dependent only on the mean blood pressure (input), the pulse pressure and P(z), and is independent of R. For those vascular beds where the impedance is largely resistive, e.g. the brain, the kidney and the uterine-placental complex, it is suggested that P(z) may be a more useful characterizing parameter than the value of PI(flow) as at present used by some workers.
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Gosling et al. (1991) studied Low-impedance vascular beds. Electrical circuit model of pulsatility index was evaluated. A simple electrical circuit model suggests that back pressure P(z) may be a more useful characterizing parameter than the pulsatility index for vascular beds where impedance is largely resistive.
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