Monitoring in Anaesthesia

Question 1

What is Beer’s Law and Lambert’s Law in relation to pulse oximeters?

Answer 1

Beer’s Law: Amount of light absorbed is proportional to the concentration of the light absorbing substance

Lambert’s Law: Amount of light absorbed is proportional to the length of the path that the light has to travel in the absorbing substance.

Absorbance of light depends on:

1. Concentration of light absorbing substance (Beer’s)
2. Length of light path in the absorbing substance (Lambert’s)
3. oxyhaemoglobin and deoxyhaemoglonin absorbs red and infrared light differently

Question 2

Awake vs anaesthetised EEG waveforms