Can anyone help
We are having problems with condensation building up in the patient circuit when using the circle system with low flows for long cases.We are also using a HME filter at the patient end of the system.We are currently trailing a new circle system with a built in heater but are still experiencing the same problem. Has anyone else experienced this problem and reached a solution.

There's bound to be condensation (rainout) (it's the laws of physics). Isn't there a water trap in there somewhere (or am I missing something here)? Do you have details of the set you are using (supplier, catalogue number, etc.)?

I assume (should I ever assume .... but you're using the phrase long cases) that you're referring to anaesthesia here KAG, rather than ICU?

I also hear the term exhaled breath condensate (EBC) being used. Is that what we are talking about?

HME: hygroscopic heat-moisture exchanger? I always thought these should not be used in anaesthesia circuits (?)

Meanwhile, here's a link for anyone else who may be interested.

Hi Geoff
We have the penlon SP Prema. Yes we are talking about long surgical casees.
Intersurgical circuit and HME Filter at the patient end. The circle system has a water trap but it have little water in it, in these long cases. The water is building up and pooling in the anaesthetic circuit limbs. Would I be right in thinking the HME filter is exacerbating the problem and we would be better off using just a bacterial filter
Thanks

I would try removing the HME altogether. As I say, I believe they should not be used during anaesthesia at all (but I'm no expert). Don't they impede the flow of anaesthetic gases? Anybody ... ?

Sounds about right.

I'm no expert but on the ICU's we considered that if the circuit was wet then we could just use a bacterial filter.
Rain out was a common problem with vent circuits on ICU patients.
Regular water trap emptying seemed to help as did checking that temp probes were seated correctly and the limb wire set to 1-1.5 oC above the heating chamber temp. Sounds simple but have the users read the manual and understood it. Based on personal experience people used to make things up as they went along with hunidifiers. Usually found incorrect settings when trouble shooting. Dr settings as opposed to manufacturer settings

Indeed, but we need to be careful here (do we not?). "Long-term" ventilation in the ICU, and "long cases" in the Theatres are two different sets of circumstances, right? One uses anaesthetic gases, the other does not. How long are these cases, KAG? Just how many hours are we talking about here?

We are talking about 4-6 hours nothing like ICU cases.
The soda lime is damp but not saturated. This problem is not experienced with shorter cases and like i say the water trap has very little water in.

Sorry to be a pain, KAG, but I think you're going to have to describe the complete circuit for us! Fresh gas outlet -> then what? Or should I say absorber outlet to patient -> then what? Where, exactly, do you place the HME (at the mouth-piece)? Does the patient inhale, and exhale, through it ... or what? Where exactly do you place the water trap (at the lowest point of the return circuit)? Sorry, but we need input!

No problem thanks for your help.
The water trap is beneth the circle system soda lime jar. The HME Filter is at the patient end of the respiratory circuit so the patient breaths in and out through the filter.

And where exactly is the excessive moisture build-up collecting (you're saying that it's building up and pooling in the anaesthetic circuit limbs, but not in the water trap)?

Meanwhile, any clues here? Or, perhaps, here?

As I say, I'm certainly no expert, but I would have thought that your patients could manage OK without an HME for the period of time you mention. I think I would try using just a normal breathing filter.

Ive experienced problems where its been the actual teperature within the theatre that has caused the rainout.
Is the theatre particularly cool compaired to the expired breathe.
Is the airway being heated etc.
Also are there any drafts from things like fans, and door air circulation systems. You'd be supprised what causes water in circuits.

Thanks for that. We will try a standard filter. I will let you know how we get on
Kev

I'm interested in all the above comments. From a theoretical view, all of the moisture breathed out by the patient should be picked up by the HME and then re-breathed in. Therefore, very little moisture should find its way to the anaesthetic machine side of the HME. It would be interesting to note what happens when the HME is replaced by a bacterial filter.
Just one further point that Geoff raised regarding an HME in an anaesthetic circuit; the HME could have the reverse effect on the vapourised anaesthetic agents and cause the "rainout" that is being seen, but only if the "moisture" levels and temperature are similar to that seen on the patient side of the HME.
Let's see what Kev finds out??!!!!!

Hello to one and all in the forum (This is my first post, lot my cherry!)

Anyway back on the subject, just wondering do they let the system "breathe" over night by letting the soda lime cannisters down. This will effectively let the system dry out over night??

Welcome to the forum, Mate. Yes, as Kawa says, this is quite an interesting one. My own hunch is that it's something to do with the HME (which I would remove myself, as I say). But this is one of those problems that it's difficult to get to grips with without a diagram, photo ... or better still, actually being there! I guess we now await news from Kev (with, as it were, baited breath)!

PS: Devon, Dorset ... or good old Somerset?

I'm from the mighty Somerset aka Avon!!

I have had running issues with Theatre staff over the use of patient tubing. (The ones which fit on the insp/exp with the y-piece) They do suffer from moisture but the main issue is that they use them for 7 day without changing and hide behind a banner of we change the filter. I would'nt want to be on the other end of a 7 day piece of tubing with moisture and expired gases from Tom, Dick or Harry (Definitely NOT Dick!!) Or maybe Im sensitive like that!

Slightly off subject!!

That's bad practice, Mate (even I know that)! What are they doing, penny pinching? Slapped wrists all around, I'm afraid!

It's not Avon now, though, is it? I remember all the fuss when it first came in. Now there's another fuss about taking it away. My own beef is with all that nonsense about South Gloucestershire (don't even ask about "North Somerset" and "Bath and North-East Somerset" ... spare me)! Just for comparison, have you seen the size of counties like North Yorkshire, Lincolnshire, Norfolk ... or even glorious Devon? Why can't the meddling idiots just leave things alone!

It is officially Somerset now and Avon has now been retired to the History books! Well what would all the idiots do if they cant think up stupid thinks like name changes instead of immigration ,crime and a spiralling economy. Ive heard its not illegal to lie in parliament but I suppose we all ready know about that!!

Just as long as our beloved E.U. doesn't ban cider, eh?

Meanwhile, back at the thread ... I wonder how Kev is getting on (having problems convincing his anaesthetist, I shouldn't wonder)!

Thanks for the imput.
Regarding the HME Filter - Geoff you were under the opinion that they were not used in anaesthetic cases is that the opinion of of others. ie: do other hospitals use Bacterial Filters or HME Filters?

Generally the hospitals Ive worked in all use Bacterial Filters, but the cases dont tend to go past 4-5 hours. Is there a price issue on the two different types. I think that this problem could be a combination of things!

Can we get this one back into play for a day or two? I feel that it hasn't yet been fully resolved!

Go back to the basic chemistry of soda lime [mainly calcium hydroxide Ca(OH)2 and sodium hydroxide NaOH] and carbon dioxide.

CO2 + H2O → H2CO3
H2CO3 + 2NaOH → Na2CO3 + 2H2O + Heat
Na2CO3 + Ca(OH)2 → CaCO3 + 2NaOH
Ca(OH)2 (heat) → CaO + H2O

One of the end products is water.

If an HME is used it will not pass to the patient, if low flow anaesthesia is used there will be little or no gas going out of the exhaust to take it away, hence it is trapped in the circuit.

Replacing the HME with a bacterial filter will allow it to go back to the patient but do you want excessive water in the patient's lungs?

Water is a natural product of using an absorber. Remove it with the water traps, if it is raining out make sure it runs down to the water traps.

Robert

My experience is on Intensive Care ventilation, not theatres, but a couple of thoughts occur to me on this. First, an HME is intended to stop the patients lungs drying out when there is no humidification of bone-dry wall gas - so if the circuit is wet there is no point using one, and a bacterial filter should do the job. (Unless you're going onto a dry vent in recovery and want to keep the same one on?). Secondly, if the HME or bacterial filter is getting wet, gas flow to the patient will be reduced giving a new set of problems!

How is the breathing gas warmed and humidified in your set-up?

Meantime, I agree that positioning of the circuit may help, to get the water to run back to the trap rather than towards the patient.

Hi Guys,
Was this issue ever resolved, or any closer to being resolved?

A question I found myself asking is why are HME's being used with an circuit, I can only assume these are not single use circuits?

What Agent/s are being used, Isoflurane, Desflurane, Sevoflurane?

Is the absorbant fresh, how often is replaced?
What are typical gas flow rates, when this 'rainout' occurs?

Dom

You also mentioned that the circle absorber was heated, is this correct?

Im thinking perhaps what you are seeing is simply rainout, due to the circle absorber being heated and the patient circuit not being heated, therefore the temp drop across the circuit is causing rainout. Perhaps!?!

Regards

Dom

The problem is with the HME (and the usage thereof)!

Exactly Geoff,
It is keeping the water from the chemical reaction in the CO2 absorber in the circuit.
See my above post for details.
Robert

I have a good recent (this morning) story on this subject. Patient intubated and just gone onto vent. Surgeon ready to go. Gas man decides he is not happy and switches to bag while ODP gets another trolley and they swap over. Now all happy, yours truely gets called. Problem turns out to be sticky valve on exp. side of APL. Reason...a few ml's of water! Woke the anaesthetist up first thing on a Monday morning I'm sure! We don't use HME filters BTW. Things aren't helped by the room air being A/C to 24C or so, but 80-90% RH!!

Any ideas for keeping things dry?