Haemodynamics Flashcards
(20 cards)
What is haemodynamics?
Describes the way your blood flows
Relationship between blood flow,pressure and resistance to flow
List factors affecting haemodynamics
Force - cardiac contraction
Work - isovolumetric contraction
Pressure - difference in aorta/veins
Compliance - arterial stretch
Resistance - arterioles
Flow velocity - slowing down blood flow in capillaries
What happens in one part of CVS has a major impact on other parts. Reduced blood flow to one area….
Increases pressure upstream and alters flow to other areas
Where is the majority of the blood ?
Venous system
Veins + venules
64%
How can the reservoir of venous blood be used to increase cardiac output?
Starling’s law
What is Darcy’s law?
List two equations for flow
Flow = Pressure difference
—————————
Resistance to flow
Outlines role of pressure energy in flow
Flow= Pa - CVP
————
TPR
What is Bernoulli’s law ?
Flow = pressure + (kinetic)^2/2 + potential
definition of blood flow
Volume of blood flowing in a given time (ml/min)
What is perfusion?
Blood flow per given mass of tissue (ml/min/g)
What is the velocity of blood flow
Blood flow is affected by the cross sectional area through which the blood flows, so flow remains the same. If there has been a change in area it changes velocity
Equation for volume flow?
volume flow (Q) = velocity (V) X Area (A)
Blood flow (Q) remains constant at 10 ml/s
Total volume flow (ml/min) stays the same
What are the 3 patterns of blood flow?
- laminar
- turbulent
- bolus
where is Laminar blood flow
arteries, arterioles, venules, veins
where is Turbulent blood flow
Ventricles (mixing)
Aorta (peak flow)
Atheroma (bruits)
Where is bolus blood flow?
Capillaries
What is Reynolds’s number?
Reynold’s number describes what determines change from laminar to turbulent flow.
Turbulence occurs when Reynold’s number exceeds a critical value (>2000), e.g. bruits, ejection murmur, increased blood velocity.
Are arterioles under parasympathetic or sympathetic control?
Sympathetic
What is the pulse pressure?
Difference between diastolic and systolic pressure
Pulse pressure equation?
Stroke volume
______________
Compliance
Why is pulse pressure more noticeable further down the arterial tree?
Vessels become less compliant
