Similar presentations:

# Haemodynamics Haemorheology

## 1. Haemodynamics Haemorheology

## 2. Branches of physics

PhysicsContinuum mechanics

Fluid mechanics

Fluid dynamics

Hydrodynamics

Haemodynamics

Fluid statics

Aerodynamics

other branches

## 3. Branches of physics

PhysicsContinuum mechanics

other branches

Solid mechanics

Fluid mechanics

Plasticity

Non-Newtonian fluids

Rheology

Haemorheology

## 4. Laminar and turbulent flow

(a) occurs when a fluidflows in parallel

layers, with no

disruption between the

layers

(b) is a flow regime that

demonstrates chaotic

changes in pressure

and flow velocity

## 5. Viscosity

• The viscosity of a fluid is a measure of itsresistance to gradual deformation by shear

stress or tensile stress

## 6. Viscosity

Viscosity is a property of the fluidwhich opposes the relative motion

between the two surfaces of the

fluid that are moving at different

velocities. When the fluid is

forced through a tube, the particles

which compose the fluid generally

move more quickly near the tube's

axis and more slowly near its

walls; therefore some stress is

needed to overcome the friction

between particle layers to keep the

fluid moving.

## 7. Newton's Law of Viscosity

dVF

S

dZ

• F is the shear stress in the fluid

• η is a scalar constant of proportionality, the shear

viscosity of the fluid

• dV/dZ is the derivative of the velocity component

that is parallel to the direction of shear, relative to

displacement in the perpendicular direction.

• S is the surface (area) between fluid and the tube.

## 8.

• Non-Newtonian fluid• Newtonian fluid

viscosity is dependent

fluid in which the

on shear rate or shear

viscous

stresses

rate history.

arising from its flow,

Shear thickening

at every point, are

(dilatant) - apparent

linearly proportional

viscosity

increases

to the local strain rate

with increased stress.

(the rate of change of

Shear

thinning

its deformation over

(pseudoplastic)

time).

apparent

viscosity

decreases

with

increased stress

## 9. Reynolds number

Is the important dimensionless quantity refers to ratio ofinertial forces to viscous forces within a fluid which is

subjected to relative internal movement due to different

fluid velocities, in which is known as a boundary layer in

the case of a bounding surface such as the interior of a

pipe.

## 10. Reynolds number

Used to help predict flow patterns in different fluid flowsituations.

At

low

Reynolds

numbers viscous forces

are dominant, and is

characterized by smooth,

constant fluid motion

(laminar flow).

At high Reynolds numbers

flow is dominated by inertial

forces, which tend to produce

chaotic eddies, vortices and

other

flow

instabilities

(turbulent flow).

## 11. Reynolds number

wherein:vs - mean fluid velocity, [m/s]

L - characteristic length, [m]

μ - (absolute) dynamic fluid viscosity, [Pa*s]

ν - kinematic fluid viscosity: ν = μ / ρ, [m²/s]

ρ - fluid density, [kg*m-3]

## 12. Pascal's law

• Pascal's law is a principle in fluidmechanics that states that a pressure change

occurring anywhere in a confined

incompressible

fluid

is

transmitted

throughout the fluid such that the same

change occurs everywhere

## 13. Bernoulli's principle

ρv2/2 + ρgh + p = const• ρv2/2 is dynamic pressure,

• ρgh is hydraulic head

• p = static pressure

## 14. Hagen–Poiseuille law

Q = ΔP πr4/8ηLflow of liquid depends on following factors: like the

pressure gradient (∆P), the length of the narrow tube (L)

of radius (r) and the viscosity of the fluid (η) along with

relationship among them.

Assumptions:

•The tube is stiff, straight, and uniform

•Liquid is Newtonian , i.e., viscosity is constant

•The flow is laminar and steady, not pulsatile, and the velocity at the wall

is zero (no slip at the wall)

## 15. Hagen–Poiseuille law

Q = ΔPπr4 / 8ηLThe Pressure Gradient (∆P) : Shows the difference in the pressure between the two

ends of the tube, determined by the fact that any fluid will always flow from high

pressure to low pressure region and the flow rate is determined by the pressure

gradient (ΔP = P1 – P2)

Radius of tube: The liquid flow varies directly with the radius to the power 4.

Viscosity (η): The flow of the fluid varies inversely with the viscosity of the fluid and

as the viscosity of the fluid increases, the flow decreases vice versa.

Length of the Tube (L): The liquid flow is inversely proportional to the length of the

tube, therefore longer the tube, greater is the resistance to the flow.

Resistance(R): The resistance is described by 8ηL/πr4 and therefore the Poiseuille’s law

becomes

Q= (ΔP)/R

## 16. Cardiac output

CO = HR × SVIs the volume of blood being pumped by the heart, in

particular by the left or right ventricle, per unit time.

## 17. Major factors influencing cardiac output

Cardiac OutputStroke Vloume

Heart Rate

Heart size

Humoral regulation

(hormones)

Contractility

Autonomic innervation

Preload

Afterload

## 18. Frank–Starling law

• The Frank–Starling law of the heart represents therelationship between stroke volume and end diastolic

volume. The law states that the stroke volume of the

heart increases in response to an increase in the

volume of blood in the ventricles, before contraction

(the end diastolic volume), when all other factors

remain constant. As a larger volume of blood flows

into the ventricle, the blood stretches the cardiac

muscle fibers, leading to an increase in the force of

contraction.

## 19. Myocardial contractility

Myocardial contractility (cardiac inotropy) represents the innateability of the heart muscle to contract. Changes in the ability to

produce force during contraction result from incremental degrees of

binding between thick and thin filaments.

This results in better ejection of the blood in the ventricles.

Controlled by extrinsic factors

• sympathetic stimulation of the heart

• hormones

• K+ and Ca++ channel blockers

## 20. Preload

Preload is the end diastolic volume thatstretches the right or left ventricle of the

heart to its greatest dimensions under

variable physiologic demand. It is the initial

stretching of the cardiomyocytes prior to

contraction; therefore, it is related to the

sarcomere length at the end of diastole.

## 21. Afterload

• Afterload is the stress in the wall of the leftventricle during ejection. It is the end load

against which the heart contracts to eject

blood. Afterload is readily broken into

components: one factor is the aortic

pressure/ pulmonary pressure the left/right

ventricular muscle must overcome to eject

blood.

## 22. Vascular resistance

Vascular resistance is the resistance thatmust be overcome to push blood through

the circulatory system and create flow.

Resistance is a factor of:

• Blood viscosity

• Total blood vessel length

• Vessel diameter

## 23. Rouleaux

Rouleaux are stacks or aggregations of redblood cells which form because of the

unique discoid shape of the cells in

vertebrates. The flat surface of the discoid

RBCs gives them a large surface area to

make contact with and stick to each other;

thus forming a rouleau.

## 24. Rouleaux

Diameter of blood vessel is more than diameter of rouleaux## 25. Rouleaux

Diameter of blood vessel is nearly equal to diameter ofrouleaux

## 26. Rouleaux

Diameter of blood vessel is less than diameter of RBC1 KC

K

4

3

2,5 R

3

## 27. Hagen–Poiseuille law

Q = ΔPπr4 / 8ηLQ= (ΔP)/R

Pressure gradient: created by the heart.

Resistance

Radius of tube: diameter of blood vessels.

Viscosity : property of blood.

Length of the tube

## 28. Now summarize three major concepts presented in this lecture

• 1.• 2.

• 3.