Neuro Monitoring Analysis

NMA Product Information

The theory of arterial acceleration is an alternative to the theory of arterial stiffness that was formulated in the 19th century and used extensively in CV research. It elaborates on the work by Harvey (1628) who was the first to realize that the heart is the driving force behind blood circulation. The theory of arterial stiffness explains the change in blood pressure profiles and blood flow velocity as they travel away from the heart down the branching arterial tree. Blood is expelled from the heart into the aorta during systole in a parabolic profile, yet when measured downstream the profile of the blood flow velocity turns into a more biphasic signal.

Arterial stiffness  proposes that this profile change occurs due to recurrent waves where the positive pressure wave from the heart reflects against the high resistance of peripheral arteries. Throughout the arterial tree the pressure measured is a combination of the forward and backward traveling waves from different points of reflection. Therefore, the reflecting waves form an obstacle to the blood flow and energy of cardiac contraction is lost which, should result in the reduction of pulse pressure and flow; of course this is not the case. 

Conversely, the theory of arterial acceleration proposes that energy is added to the pressure wave as it travels away from the heart. The increase in aortic pressure at stroke onset triggers the myogenic response in smooth muscle cells. This stretch induced depolarisation spreads rapidly via gap junctions between individual cells. Thereby a wave of depolarisation sweeps along the arterial tree from proximal to distal and into the most remote capillary systems. The depolarisation triggers calcium influx resulting in a short lasting contraction of the smooth muscle cells.

In this way arterial acceleration augments the pressure wave from the heart traveling at high speed as a peristaltic wave along the arterial tree. Since it is at stroke onset and short-lasting it does not interfere with the ejection phase of the heart. The arterial acceleration allows the pressure generated during the first instances of contraction to spread along all branches of the arterial tree and enter into even the most remote capillary systems.

Arterial acceleration assumes the change in modelling from lumped models, assuming a uniform distribution of blood flow over the entire blood vessel at any moment in time, to complex 3D modelling representing the entire arterial tree requiring a change in our interpretation of existing information. To quote Lord Kelvin “I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it;” the requirement is to introduce new Doppler waveform parameters to adequately express the potential for each cardiac cycle.

Neuromon B.V. have developed advanced modelling which is now incorporated in the NMA software introduced in DWL TCD systems enabling detailed waveform analysis of arterial blood pressure and blood flow to the brain. Improved TCD waveform analysis with enhanced parameters allows discrimination of pathology in patients from normal controls, revealing the relationship between pressure and flow demonstrating the scope of a single heart beat beyond existing TCD parameters such as TAMV and PI measures introduced in the early 1980’s.

NMA software analysis the pulse contour of every CBFV waveform and derives the new TCD parameters providing trending and normalisation of data by age and sex. Doppler parameters and can be used, among other things, in surgery, anaesthesia and intensive care  providing innovative screening for physicians and healthcare professionals to quickly and reliably interpret the TCD signal in complex clinical situations 

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