If an anaesthetist at high altitude uses plenum vaporizers. It will deliver the vapour concentration –
Plenum vaporizer is typically set to deliver a 1-2 kPa partial pressure of anaesthetic agent. At sea level, where atmospheric pressure is around 100 kPa, this equates conveniently to a concentration of 1-2% of anaesthetic agent (1-2kPa out of 100 kPa).
At higher altitude, the atmospheric pressure is low (e.g. 75 kPa). The plenum vaporizer deliver 1-2 kPa partial pressure of anaesthetic agent. So, the concentration of anaesthetic vapours will 1.25 - 2.5% → Greater than the concentration of anaesthetic agent at same partial pressure at sea level.
Higher than the original concentration at high partial pressure
Lower than the concentration at lower partial pressure
Higher than the concentration at same partial pressure
Lower than concentration at same partial pressure