O2 flow rates

Re: O2 flow rates

Paulette — Wed, 12 Dec 2012 21:26:47 GMT

hello :)

I'm used to using ADE now so I know how 'normal circuit' flow rates must seem shockingly high now! I always used to find that the 'inbetweeney' dogs ie 7 or 8kg did well on a Bain circuit. Flow rates are high so not v economical but can use 1litre bag in conjunction with the high flow rate so perhaps dog will be less huffy as can draw appropriate amount of fresh gas? good to use capnograph with this if you can. May be worth asking if you can invest in a Bain? other obv benefits of Bain are good for IPPV etc. circuit factor same as t-piece (2.5/3) hence high flow rates. or as prev poster said Mini lack may be good too. hope this helps a little :)

Re: O2 flow rates

Julie-Anne Wilson — Wed, 12 Dec 2012 07:33:19 GMT

I think (can't remember exactly) the dog's respiration rate was 30-something but other than that my calculation was exactly the same.

Maybe it was just a fluke anaesthetic reaction that happened to coincide with me trying out the proper calculations. I'll see how I get on next time and maybe if I come out with that figure again, I'll simply just turn it down a couple litres.

Thanks for the answers everyone.

Re: O2 flow rates

Emma Wills, Cert AVN (Anaesthesia) RVN — Wed, 12 Dec 2012 00:59:19 GMT

Do you mind sharing your calculations?

Dependent on the patients RR, I worked on a RR of 20 as a small dog, (if it's RR was higher than 25 then your calculations are right and I would just suggest a mini lack or a circle with a 0.5l bag and small smooth walled tubes) avail at www.aasbiomedical.com/breathing-circuits

7.5kg x 15ml/kg =112.5ml/kg/hr

112.5ml/kg/hr X 20RR = 2250ml (2.25L/min)

2250ml x 2.5 (cf) = 5625ml/min (5.63L/min) or 2250ml x 3(cf) = 6750ml/min (6.75L/min)

T-piece requires high flow rates and I wouldn't have anything lower than 3L on this circuit.

Circle in general you start them at 60ml/kg for 10mins, then reduce down to 30ml/kg. If capnography in use, perfectly safe to take O2 down as low as the cap says you can. I've had them down as low as 0.3l/min.

Hope this helps and I hope I'm not teaching you to suck eggs!

Re: O2 flow rates

Kelly Hempenstall — Tue, 11 Dec 2012 23:52:20 GMT

For the circle circuit you can use 10ml/kg 02 but also start higher to denitrogenise the circuit for 10 minutes. Generally start on 3-4L then reduce to 2L and consider then weight of the patient. I usually use the circle on 1L O2 and use a capnograph at all times.

Re: O2 flow rates

Celine — Tue, 11 Dec 2012 21:09:19 GMT

I'm not entirely sure to be fair - your servicing person would be able to tell you at the time they service it what values are coming out of the vaporiser at each O2 level?

Sorry I can't help more! Maybe give you service guy a call?

Re: O2 flow rates

Julie-Anne Wilson — Tue, 11 Dec 2012 20:37:27 GMT

SP02 was fine. The machine was last serviced in June (or July) - actual flow rate calculation came out at 10l/min but that is right at the top of the tube so I had it down at about 9, which just seemed so high. I've been working with the ADE for the last year and a bit and I was out of nursing for 4 years before that so I honestly couldn't remember what the rates should be.

I can see what you're saying about the vaporiser not keeping up but, if that's the case, what should I do when I get high flow rates? Is there any different calculations for that scenario?

Re: O2 flow rates

Celine — Tue, 11 Dec 2012 19:41:36 GMT

Do you mind if we ask what rate you had it on then? I cant imagine you would, but if your flow rate is right at the top of your o2 (gauge? what do you call the tube the little baffle floats up and down in??) then its very likely the vaporiser cant keep up and you're not giving the amount of anaesthetic agent you think you are..ref Mr David Burton of Burtons Medical . also, when was the vaporiser last serviced? Because if it is at all dodgy and you suddenly stsrt using more o2 than you usually have then you will be getting unusual ga results...

Youre sure the dog didnt have any lung / heart pathology? Do you have SPO2 or a capnograph?

Re: O2 flow rates

Julie-Anne Wilson — Tue, 11 Dec 2012 18:17:35 GMT

Yeah, I get the 1l thing on circles, I don't like having them low.

The dog was a 7.5kg Lhasa Apso

Re: O2 flow rates

A-J — Tue, 11 Dec 2012 09:49:30 GMT

how big was the dog?

Re: O2 flow rates

jules007 — Tue, 11 Dec 2012 08:28:46 GMT

we calculate our flow rates and use the 2.5-3 CF for t-piece and with the circle start them off with 3L for 10 minutes and then reduce to 2L thereafter. You can use the circle at 1L flow rates but people here just don;t feel comfortable with that.....