Abstract
Objective. Cerebral autoregulation is critically important to maintain proper brain perfusion and supply the brain with oxygenated blood. Non-invasive measures of blood pressure (BP) are critical in assessing cerebral autoregulation. Wave propagation velocity may be a useful technique to estimate BP but the effect of the location of the sensors on the readings has not been thoroughly examined. In this paper, we were interested in studying whether the propagation velocity of a pressure wave in the direction from the heart to the brain may differ compared with propagation from the heart to the periphery, as well as across different physiological tasks and/or health conditions. Using non-invasive sensors simultaneously placed at different locations of the human body allows for the study of how the propagation velocity of the pressure wave, based on pulse transit time (PTT), varies across different directions. Approach. We present a multi-sensor BP wave propagation measurement setup intended for cerebral autoregulation studies. The presented sensor setup consists of three sensors, one placed on each of the neck, chest and finger, allowing simultaneous measurement of changes in BP propagation velocity towards the brain and to the periphery. We show how commonly tested physiological tasks affect the relative changes of PTT and correlations with BP. Main results. We observed that during maximal blow, valsalva and breath hold breathing tasks, the relative changes of PTT were higher when PTT was measured in the direction from the heart to the brain than from the heart to the peripherals. In contrast, during a deep breathing task, the relative change in PTT from the heart to the brain was lower. In addition, we present a short literature review of the PTT methods used in brain research. Significance. These preliminary data suggest that the physiological task and direction of PTT measurement may affect relative PTT changes. The presented three-sensor setup provides an easy and neuroimaging compatible method for cerebral autoregulation studies by allowing measurement of BP wave propagation velocity towards the brain versus towards the periphery.
Highlights
Autoregulation of cerebral blood flow is a critical mechanism of the brain to maintain a relatively constant supply of blood flow in the face of changing perfusion pressure (Madsen et al 1990)
We demonstrated that the blood pressure (BP) wave propagation time measured from the chest to the brain and from the chest to the periphery differs strongly depending on the physiological task, as well as correlating differently when compared with BP values measured using Finometer
A third sensor placed on the finger measures BP pressure propagation velocity simultaneously towards the periphery
Summary
Autoregulation of cerebral blood flow is a critical mechanism of the brain to maintain a relatively constant supply of blood flow in the face of changing perfusion pressure (Madsen et al 1990). In this mechanism, the cerebral arterioles adjust vascular resistance in response to reductions and elevations in blood pressure (BP), thereby preventing damaging hypoperfusion and hyperperfusion of the brain, respectively (Paulson et al 1990). ABP in cerebral autoregulation studies is commonly measured using an invasive catheter or non-invasive monitoring based on the volume-clamp method, such as Finapres. Finding a non-invasive alternative method of measuring BP for cerebral autoregulation studies is of high interest
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