gms | German Medical Science

Introduction: Non-invasively, blood pressure (BP) is typically measured via cuff-based oscillometry (NIBP). NIBP however is an intermittent measurement which has been clinically reported as highly inaccurate in hypo and hypertension [1]. At the same time, cuff devices offer ample possibilities to modulate blood flow and pulse propagation along the artery. The vasculature response to occlusion perturbation is an underutilized source of information and can be explored to achieve more accurate, continuous and specific BP measurements; e. g. simultaneous measurement of electrocardiogram, photoplethysmogram and cuff pressure can facilitate BP-surrogate calibration. In addition, observation of cuff-induced effects may enable estimation of arterial compliance, peripheral resistance, mean systemic filling pressure [2]. However, assumptions are still required to explain observed cuff-induced vascular behavior. Additional research modalities are needed for further development of cuff measurements and for implementation of such measurements in standard practices.

Methods: In this study, we employed MRI to provide new insights over the influence of the cuff on arterial pulsations. We perform 3D T1 weighted fast field echo (FFE) and retrospective gated balanced turbo field echo (TFE) CINE scans on 12 healthy participants to observe vasculature, tissue, cuff interaction.

Results: The images provide insights into several assumptions. Unpredictable cuff folding occurs during inflation; compression of the arm is not isotropic (Figure 1 [Fig. 1]). This effect possibly hinders accurate modulation of arterial transmural pressure. The artery location is subject dependent; oscillations of superficial arteries are likely expressed differently than oscillations of arteries located within subcutaneous fat. Complex tissue compression/displacement occurs under the cuff; arterial volume pulsations might not be equivalent to arm volume pulsations. The technique also allows to estimate the lumen area of the brachial artery and how it changes due to cuff pressure or systemic blood pressure of the subject [3]. The images reveal non-linear collapse characteristics and non-uniform collapse across the length of the cuff. No significant changes in arterial properties were detected during two consecutive inflations. This suggests that compensatory mechanisms are not activated in healthy subjects due to transmural pressure modulation via the cuff. However, systematic differences are observed when comparing vasculature response to inflation vs. deflation; complementing results acquired via alternative research methods [4].

Conclusion: It is found that MRI provides a novel perspective over oscillometry; the artery, surrounding tissue, veins and the cuff can be simultaneously observed along the length of the upper arm, as well as distally from the cuff. Several existing assumptions are challenged, the cuff interaction with the vasculature is oversimplified by existing models. The results are essential for improving existing BP measurements and enabling measurement of arterial compliance, peripheral resistance and beat-to-beat BP. MRI is an essential research tool for further development of cuff-based physiological measurements [5]. In this work we summarize the findings of our recent research on this topic.

Laura Bogatu, Lars Schmitt and Jens Muehlsteff are employees of Philips.

The authors declare that a positive ethics committee vote has been obtained.

This contribution has already been published: This abstract is an aggregated view of our recent research and it has been in part published at other conferences. Therefore, we could conclude that this abstract in its completion has not been published.