Modern vaporizer splits stream of gas into bypass gas (not not enter vaporizer chamber) and carrier gas (does enter vaporizer chamber) to deliver accurate vol %
What method of vaporization do the modern machines use? The old ones?
Modern- flow over
Old- bubble thru
What type of vaporizer uses injected method of vaporization?
How do MAC and vol % relate when using a vaporizer?
We set volume %, but must take MAC into account. For example sevo's mac = 2, so at a vol % of 1, you are at half a mac.
What factors can affect vaporizer output?
1) T- as temp increases so does VP (but modern vaporizers compensate for this)
2) carrier gas (at very high or low flow rate less anesthetic will be delivered), ok btw 250 ml/min to 15 LPM
-identity of carrier gas
3) intermittent back pressure
4) altitude (but vap adjusts splitting ratio)
Why would giving 100% N20 as carrier gas be harmful?
N20 dissolves in the volatile anesthetic initially and leaves less carrier gas available to pick up and deliver volatile agent. This effect lasts for only 15 mins, but volatile output will be decreased by 10% for that time.
What is the "intermittent back pressure" or "pumping effect"?
Occurs with pos. pressure ventilation (spont or controlled), pressure is transmitted back to the vaporizer and drags more volatile agent with it, so more volatile agent is given than is dialed by the CRNA.
If we were giving anesthesia on the top of a mountain with decrease atm pressure with a copper kettle, how would this affect conc of volatile delivered?
More would be delivered.
iso makes up a larger proportion of pressure
Why is des special?
-It must be stored in a pressurized container (makes it less volatile since its VP and BP are close to RT and atm P)
-Needs a heated vaporizer
Why does des need a special vaporizer with a heat source ?
It has a high MAC (low potency) so you need to give a large amount, process of vaporization is cooling, so could immediately cool is there were no external heating mechanism.
Can you refill the iso vaporizer while it's on?
NO, only the special des vaporizer can be refilled while in use (closed system)
What happens if you overfill or tip over a vaporizer container?
Agent can enter the bypass chamber and more volatile will be given to the pt