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Joined: Apr 2008
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Visionary
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Visionary
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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!

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Super Hero
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Originally Posted By: KAG
... do other hospitals use Bacterial Filters or HME Filters?

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

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Hero
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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

Last edited by RoJo; 21/04/08 12:41 PM.

My spelling is not bad. I am typing this on a Medigenic keyboard and I blame that for all my typos.
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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.

Joined: Jan 2006
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Scholar
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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

Joined: Jan 2006
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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

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

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Hero
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Hero
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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


My spelling is not bad. I am typing this on a Medigenic keyboard and I blame that for all my typos.
Joined: Feb 2008
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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?

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