EBME Forums Forums Maintenance Technical Assistance vaporizer conversion

Hi all,
we have new anesthesia machines , quite nice , unfortunatly delivered with Iso ans Sevo vaporizers.
unfortunatly , because here the reference is Halothane , and Iso & Sevo are not an option.
we are going to use the Isoflurane vaporizers with Halothane , as the chimical behavior of Iso/Halothane are quite similar , that the vaporizers are new and never been filled with Iso, that they are pour-fill type , and because this kind of swap has already be done safely.
of course , the labels will be changed , and an check with gas analyser be done to have the calibration curve attached to the vaporizers.
can i have your feelings , advices or objections to this type of conversion , if any ?
thanks for your support!

best regards

Jean Michel

No technician in a UK hospital would contemplate doing such a thing as our ass would be in a sling - even if it worked ok.

Hi Kit,
i do agree with you , but unfortunaly,we are not in UK.
is it better to grab from a dusty hospital warehouse an halothane vaporizer , not knowing how long it has spent there , and with no clues about the last maintenance , and use it with a false feeling of being safe because it was sold 20 years ago for halothane use ? or is it better to to use new vaporizer and convert it to halothane , double checking the possibility to do it and verifing the output with a gas analyser ?
well , i was especting old stories from Geoff describing an unusual issue with this type of conversion
thanks for your input , i keep it in mind

best regards

Ps :
http://www.ncbi.nlm.nih.gov/pubmed/6870010
http://www.medscape.com/viewarticle/429544_2

I saw your first post when you made it, Jean Michel, but thought I had better "hold fire" on this one (so to speak) ... if only to allow others more current than myself to have their say.

Personally, and from the technical point of view, I see no problem in proceeding as you have suggested.

My only real comment would be:- "What does the anaesthetist say"? After all, it is he who takes ultimate responsibility.

Beware of halothane and vapourisers over the long term. It can leave behind a thick residue so the vapourisers need regular servicing and cleaning.
I understand where you are coming from.....this is the situation, now make it work. It is far from ideal but the reality for some parts of the world.
I think the monitoring is the essential part as long as you know what the patient is receiving it should be safe.
Robert

Indeed. And that's another reason why, on balance, it's a better plan to use the new Sevo vaporizers and not the twenty-year old Halothanes laying (but probably still half-full) in the "dusty warehouse".

Sometimes biomeds have to make a judgement call. Compromise? Real-world engineering is full of compromises. And not just engineering compromises, come to think of it.

"Needs must" comes to mind.

A while back I was a visitor (For 1 day) to a company that assembled vaporisers. Their research chemist took us to their lab and showed us some experiments they were doing on o-rings. They had O-rings suspended in glass jars above anaethetic agents to see how the o-rings reacted to different agents over time. It was a bit of an eye opener to see how some o-rings were unaffected, some had expanded to twice their original size, some had disintegrated entirely ect. I have no experience with the materials in these vaporisers, but just be aware, different agents do react differently with the materials they come into contact with. My question would be, is all the materials in a Isoflurane vaporisers suitable to be exposed to Halothane?

That's an interesting comment ... and a valid question; to which I would reply something along the lines of "that is why vaporizers need to be serviced and calibrated now and then" (generally once a year).

I would have to question the chemist's methods though - he is not testing to "real world conditions"! O-rings are invariably constrained during use (usually mechanically), rather than just being wafted about in vapour(s).

Are we just saying that some O-rings are of poor quality (which is undoubtedly true), or to be aware of using ones made of certain materials? And which anaesthetic agents rendered the most problems (which one seemed to be the most hostile to O-rings)? More information required!

Also, how long was the "time" - hours, days ... years?

Hi Guys,
just for illustrate the average machines in use here :
https://goo.gl/photos/pELJiH7M8eW1qXsC6
https://goo.gl/photos/hzNQycQXm9mggUr49

thanks for all the infos !

best regards

FMIC, I can appreciate your difficulties, we live in a different world in comparison, I hope you manage to get your setup working whichever decision you take .

Geoff, we didn't go into too much detail about the specifics of the 0-rings experiments on the day as I was there more to see how a modern anaesthetic machine is built from scratch. I did find the research chemists presentation interesting though as she was trying to show us how they need to consider the interaction of agents on various materials such as o-rings, patient circuits, tubes ect and analyse what chemicals are given off in mass spectrometers to see if there could be anything going into the patient that could cause some adverse effect, maybe not seen immediately but which could manifest sometime later.