Haemodynamics Flashcards
What is haemodynamics?
The physical factors that control blood flow
What dictates the delivery of blood to different organs?
The metabolic demands of the organs
What determines the way that blood moves?
The pressure gradient
(High pressure to low pressure)
Flows as a fluid from a high pressure to a low pressure
What is the composition of blood?
Red blood cells
White blood cells
Plasma
What is serum?
Plasma with no clotting factors (no platelets …)
What is the affect of heparin on the blood?
Makes it unable to clot
How can the whole blood viscosity change?
How does this affect the blood?
Changes in number of blood cells:
Polycythaemia (more RBCs/higher Haematocrit)
Thrombocythaemia (more platelets)
Leukaemia (more WBCs)
Thicker sludge blood - gangrene in peripheries
How can plasma viscosity change?
Plasma protein composition can change
-fibrinogen
-c reactive proteins
What is C-reactive protein used to measure?
Inflammation
High usually indicates bacterial infection
What is the FLOW of blood?
Volume of blood transferred per unit time
Ml/min or L/min
What is pressure and what is blood pressure measured in?
Force per unit area exerted by the blood
(mmHg) mm of mercury
What is cardiac output? (Equation)
CO = stroke volume x heart rate
What is stroke volume?
Volume of blood squeezed out of the left ventricle every cardiac cycle
What factors influence FLOW of blood?
Conductance (ease of flow/resistance)
Pressure gradient/difference
What equation can relate flow to conductance and pressure difference?
Flow = conductance x pressure difference
What is vascular resistance?
Resistance to blood flow in blood vessels
How are resistance and flow related?
Inversely proportional
As resistance increases flow decreases
What factor is normally changed if flow needs to be increased to an area?
Resistance decreased
What are the 2 types of blood flow?
Laminar flow (smooth/silent and maintains energy, travels in stream lines)
Turbulent flow (disorganised, noisy energy lost)
What is a stenosis?
Abnormal discrete narrowing of an artery or open area of a heart valve
What point does laminar flow become turbulent?
When flow can not increase proportionally to match the increased pressure in the blood vessel
What is the point called which pressure increases beyond which flow can match it linearly so flow becomes turbulent?
Critical Reynolds number