Electrical impedance plethysmography versus tonometry to measure the pulse wave velocity in peripheral arteries in young healthy volunteers: a pilot study

Figures

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  Figure 1. Illustration of posterior tibial artery with the tonometer between the four electrodes.

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  Figure 2. Analysis with the intersecting tangents method of the pulse wave forms to estimate the pulse arrival time showing part of two example recordings. (A) Tonometer. (B) Negative value of bioimpedance.

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  Figure 3. An indication of the difference between the tonometer (orange) and the bioimpedance (blue) for the estimated pulse arrival time (PAT) in milliseconds displayed in a distribution. The PAT was estimated in the a. femoralis, a. popliteal, a. tibialis posterior and a. dorsalis pedis in nine healthy participants during a five minute measurement. Each column represents an artery, and each row represents a participant. The a. dorsalis from one subject and a. femoralis and a. popliteal from another were removed from the data due to poor signal quality hampering pulse detection from either tonometer or bioimpedance signals.

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  Figure 4. The relation between bioimpedance and tonometer measurements plotted along an x=y line in the a. femoralis, a. popliteal, a. tibialis posterior and a. dorsalis pedis using the mode from the nine healthy participants for (A) the estimated pulse arrival time (PAT) in milliseconds and (B) the calculated pulse wave velocity (PWV) in meters per second based on the PAT modes and measured distances between the arteries.

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  Figure 5. The distribution is displayed in boxplots, which are made of the interquartile ranges of the pulse arrival times (PAT) in milliseconds (ms) estimated by the bioimpedance (Z) and tonometer (T) from the nine healthy participants for the a. femoralis, a. popliteal, a. tibialis posterior and a. dorsalis pedis. First the interquartile ranges of the PAT for every artery from all the participants were determined. Subsequently a distribution of these interquartile ranges was made. The average interquartile range for bioimpedance (Z) is 11.48 ms and for tonometer (T) is 9.44 ms in all arteries.

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  Figure 6. The distribution of the estimated pulse wave velocity (PWV) in meters per second (m/s) between the heart-a. femoralis; a. femoralis-a. popliteal; a. popliteal-a. tibialis posterior and a. popliteal-a. dorsalis from nine young healthy subjects by bioimpedance (Z) and tonometer (T) based on the mode of the pulse arrival time (PAT) in the arteries and distance between the measured sides.

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  Figure 7. Bland-Altman plots for pulse wave velocity estimates for IPG method versus tonometry, showing the difference between the paired IPG and tonometer estimates versus the paired means. The bias is shown in the solid line and the 95% limits of agreement in dashed lines. *This pair had a negative mean value due to a large negative value for the tonometer estimate. In this case, the IPG estimate only was used as the mean value.