Surplus hemodynamic energy (SHE) in blood flow

Surplus hemodynamic energy (SHE) in blood flow is the extra energy generated by a pulsatile device when adequate pulsatility is achieved. It is a measure of the amount of energy in the blood flow that is available to overcome resistance and deliver oxygen and nutrients to the tissues.

SHE is calculated by subtracting the mean arterial pressure (MAP) from the energy equivalent pressure (EEP). The EEP is a measure of the total energy in the blood flow, taking into account both the pressure and the flow rate. The following formulas can be applied to specifically calculate MAP, EEP and SHE.

Energy Equivalent Pressure (EEP)

= mmHg........................................(1)

Where P is pressure in mmHg

Q is flowrate in mL/min3

Mean Arterial Pressure (MAP)

= mmHg…........….........................................(2)

Surplus Haemodynamic Energy (SHE) = 1332(EEP-MAP) erg/cm3 ..................................(3)

Where 1332 is the empirical constant converting pressure (mmHg) to energy (erg/cm3)

Relative SHE (rSHE) = (EEP-MAP)/MAP .......................................................................(4)

Where rSHE is dimensionless

Total Haemodynamic Energy (THE) = 1332 EEP erg/cm3 …............................................(5)

An illustration:

SHE is important for several reasons. First, it helps to overcome the resistance of the blood vessels and deliver blood to the tissues. Second, it helps to maintain organ function, particularly in organs such as the brain and kidneys. Third, it helps to prevent thrombosis (blood clots).

SHE is reduced in a number of conditions, including heart failure, peripheral artery disease, and aortic stenosis. This can lead to a number of problems, such as tissue ischemia and organ damage. SHE can be increased by using pulsatile devices, such as left ventricular assist devices (LVADs) and pulsatile heart-lung machines.

Understanding the role of SHE, Triphasic Medical has developed and built a unique, patented pump to allow control of SHE in flow loops and future applications in cardiopulmonary bypass surgery, peripheral vascular disease and ventricular assist devices.

The Triphasic Waveform: An Indicator of Healthy Pulsatile Blood Flow

Healthy pulsatile blood flow in peripheral arteries is characterized by three distinct phases:

1. Systole: A rapid increase in forward blood flow (antegrade) velocity with a sharp peak occurs when the heart contracts.

2. Early diastole: Reverse blood flow (retrograde) velocity is observed as blood flows back towards the heart as the muscle relaxes and the ventricles refill with blood.

3. Mid to Late Diastole: A small slow antegrade reflective wave is generated by proximal compliant large and medium arteries.

An absence of triphasic waveform in blood flow can be a sign of arterial disease, such as atherosclerosis. The narrowing of blood vessel lumens and reduction of blood flow can lead to a loss of early diastolic flow reversal and antegrade flow during mid to late diastole, resulting in biphasic or monophasic waveforms.

Doppler ultrasound is used as a gold standard for measuring and diagnosing blood flow profiles[LB1] . The severity of the peripheral vascular disease can be determined by doctors and surgeons using doppler ultrasound as the waveforms indicate the severity of the occlusion. This will then dictate the type and urgency of intervention necessary for the level of peripheral vascular disease detected. If occlusions in blood vessels are left untreated, a patient is at risk of a heart attack, stroke, limb loss and other complications.

Having a deep understanding of the importance of triphasic waveforms in pulsatile blood flow has allowed our team to develop and build a unique pulsatile pump capable of replicating the three physiological flow profiles of varying disease states.

Initially the technology is being used in laboratories and research institutions in Germany, the Netherlands and Australia for developing new femoral catheter, performing ex-vivo liver and studying risk factor of coronary bifurcation angle.

This unique, patented pump is being further development for future applications in cardiopulmonary bypass surgery, peripheral vascular disease and ventricular assist devices.

Stay up to date with all matters in terms of pulsatile pump.

The Circulatory system.

When searching this topic there is an overwhelm of information available.

In this blog we look and main function of blood which is the delivery of nutrients, oxygen and the removal of CO2 to all parts of the body, organs and cells. Blood is a complex fluid that consists of several components, including red blood cells, white blood cells, platelets, and plasma. Overall, the main function of blood is to maintain homeostasis in the body by transporting essential substances and helping to regulate body temperature, pH, and electrolyte balance.

Whilst arteries and veins, with architecture specific to an anatomical region, present ample of complexity, the delivery to the actual cells happens at the ‘coalface’, through the microvasculature.

The capillaries have diameters ranging from 0.008-0.01 millimetres and the biophysiological behaviour of the blood flow has many aspects to consider such as viscosity and the hydrodynamic resistance determines the overall blood flow for a given perfusion pressure and the number, size and arrangement of micro vessels, their diameters, and on the viscosity of blood. Red blood cells, the volume, also known as haematocrit, have influence on the apparent viscosity as well as the speed of flow.

The Triphasic algorithm takes these and many more in consideration when calibrating the pump to deliver.

The Team@Triphasic.