Description

The PWI™ (Pulse Wave Index) is an indicator that relies on characteristics of the pulse wave shape (pulse amplitude and rise time) rather than on pressure values and its calculation is independent of the blood pressure. Studies suggest that, if taken together with the oscillometric ABI, it is the indicator with the highest sensitivity to determine PAD (peripheral arterial disease):

“In our study, PWI performed better than oABI and dABI. This finding is new, but not surprising as PWI is highly influenced by the time-to-peak of the volume curve. This parameter is known since long to be very sensitive for post-stenotic flow curves and tends to be less affected by vessel wall characteristics like media sclerosis.”

Diagnostic accuracy of ankle-brachial index by Doppler-based versus four-point oscillometry based measurements; Mayr, Hirschl, Klein-Weigel, Girardi, Kundi; Vol. 48/6 – 2019, VASA – European Journal of Vascular Medicine

Due to the increased sensitivity of the PWI, it is possible to ascertain a pathological deviation when the body is in a state of rest already, although the ABI-value may still be normal for the patient. As it can be recorded during a regular oscillometric measurement, PWI is a time-efficient method to early detect PAD and in addition has a high patient acceptance. Also, the PWI acts as an indicator for a better evaluation of vascular therapies, especially before and after interventions.

Measurement Principle

PWI is calculated as the higher maximal pulse amplitude of the upper extremity (left or right wrist) divided by the maximal pulse amplitude measured at the respective lower leg (left or right ankle) and then multiplied by the respective ankle rise time of the pulse wave: