Physics in Anaesthesia: Part 1

Question 1

State Fick’s Law

Answer 1

Blood flow to an organ can be determined if these variables are known:
a. amount of substance taken up per unit time
b. concentration of substance in arterial blood
c. concentration of substance in venous blood

Question 2

State the equation for Fick’s law of flow

Answer 2

organ blood flow = [rate of uptake] / [CONCa - CONCv]

Question 3

How can you measure liquid flow

Answer 3

1. drop counter
2. Fick principle
3. dilution techniques
   - thermal
   - dye
   - isotopes
4. variable orifice flow meter
5. electromagnetic flow meter

Question 4

What is the equation for arterial oxygen content

Answer 4

CaO2 = (Hb x SaO2 x 1.34) + (PaO2 x 0.003)

Question 5

What is the equation for delivery of oxygen in litres per minute

Answer 5

DO2 = (cardiac output) x (CaO2)

[Cardiac output = (stroke volume) x (heart rate)]

Question 6

What is the correct sizing for a non-invasive blood pressure cuff

Answer 6

Length: 2/3 of the upper arm length
OR
Diameter: 20% larger than arm diameter