L2 BLOOD FLOW

Question 1

what is blood flow for

Answer 1

• Delivery of oxygen and nutrients
• Removal of waste product of metabolism
• Distribution of heat
• Endocrine and paracrine signalling
• Delivery of immune responses to infection

Question 2

oxgen content of the blood =

Answer 2

oxygen bound to Hb and oxygen dissolved

DO2 = CO ((oxygen bound to Hb) + (dissolved oxygen))
eDO2 = CO ( oxygen bond to oxygen) 
eDO2 = CO( SaO2 x [Hb])
eDO2 = (HR x SV) x (SaO2 x [Hb])

key determiantn of oxygen delivery :

• CO
• Haemoglobin saturation SaO2
• Haemoglobin concentration ([Hb])

Question 3

what is ohms law

Answer 3

Pressure differences in the form of cardiac output and vessel compliance create blood flow.
This governing principle is quantified by Ohm’s law of fluid flow which states the following where flow (Q) is equal to the pressure gradient (ΔP) divided by resistance (R): Q = ΔP/R

Question 4

measuring blood flow using the fick principle - what is this

Answer 4

The Fick Principle simply states that at rest, the oxygen going into an organ minus the oxygen left out of an organ must equal how much oxygen that organ has used. Using the Fick Principle’s equation of (cardiac output = oxygen consumption/arteriovenous oxygen difference)

Question 5

what things do you need to know to calculate blood flow using fick principle

Answer 5

• The aount of a marker substance taken up per unit time
• Conc of marker in arterial blood
• Conc of marker in venous blood
• Dilution proportional to blood flow
  Markers that been used include oxygen, co2 ,lithium and heat and cold
  Swan-ganz catheter ( pulmonary artery catheter) – complications reasons

Question 6

how can an MI disturb blood flow

Answer 6

reduced contracigltiy because of muscle damage as well as occlusion of vessels reduces flow.

Question 7

good measure of fluid levels in body

Answer 7

JVP

Question 8

if you have treated or exclude problems of rate and filling but the flow remains too low you need to either increase the

Answer 8

contractility with an ionotrope or increase the SVR with a vasopressor.