Physics, Statistics, & Equipment

Question 1

What is the equation for specific heat capacity?

Answer 1

c = dE/m x T

Question 2

What is the greatest contributor to heat loss?

Answer 2

Radiation - 40%

The other contributors are:
- Convection at 30%
- Evaporation at 15%
- Respiration at 10%
- Conduction at 5%

Question 3

What are the three phases of heat loss under anaesthesia

Answer 3

Redistribution
Linear
Equilibrium/ plateua

Question 4

Briefly explain how a sevofluorane vaporiser works

Answer 4

Fresh gas flow enters a chamber containing sevofluorane liquid. Given enough time there will be full gas mixing and equilibration so the partial pressure of sevo will be its SVP i.e. 22kPa. To control this, there is a bypass channel that shunts FGF around the vaporiser. By controlling the proportion of FGF that goes through the vaporiser, and ensuring full equilibration for any gas that does (baffles, wicks, bubbles), you can control the percentage content of the delivered gas that contains sevofluorane. This is achieved by altering the splitting ratio, which is controlled by the vaporiser diall.

Question 5

What two adaptations address the energy loss via latent heat of vaporisation in vaporisers, which would reduce SVP

Answer 5

1) Heat sinks
- The surrounding metal is a good conductor of heat and so allows the temperature drop due to loss from latent heat of vaporisation to equilibrate with the outside