Technology

Principle of operation

VascAssist gives you two independent parameters which enable early diagnosis of PAOD: ABI and PWV.

ABI (Ankle Brachial Index)

For the determination of the Ankle Brachial Index, (ABI), VascAssist uses two independent blood pressure measurement devices working on oscillometric principles with stepwise reduction of pressure. One of the two blood pressure measurement devices is exclusively for arm measurements, the other exclusively for ankle measurements. Depending on the limbs the user involves in the measurement, the blood pressure parameters systole and diastole and the pulse are first measured on the patient's right side. VascAssist contains blood pressure modules which we have developed ourselves and for which we can influence the internal measurement algorithms. This means that VascAssist is optimized for the determination of its measurement parameters. Measurements for arm and ankle are almost simultaneous. Then if appropriate an automatic switch of sides takes place, so that the parameters mentioned before are measured almost simultaneously for arm and ankle on the patient's left side.
The ABI is determined using the following algorithm:
right ABI = systolic blood pressure of right ankle / higher of the two arm systolic pressures.
left ABI = systolic blood pressure of left ankle / higher of the two arm systolic pressures.

baPWV (brachial ankle Pulse Wave Velocity)

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Measurement of wave velocity between arm and ankle (brachial ankle pulse wave velocity, baPWV) is also performed oscillometrically. Arm and ankle blood pressure cuffs are inflated to the mean arterial pressure (MAP) of the patient if this could be determined in a prior ABI measurement. Then the mean delay is determined between arm and ankle based on multiple pulse waves free of artifacts. For the calculation the pulse curves for arm and ankle in the region of the systolic increase are overlaid and moved until the discrepancy between them is minimized. The resulting time delay (pulse wave duration) together with the height of the patient as entered into the device are used to calculate the pulse wave velocity that is then displayed. The switchover of sides takes place in the same way as for the ABI measurement.