calculating oxygen cylinder attached to a ventilator duration

[ketap]

hi..i don't know if this is the right and appropiate place to ask this, but as far as i know anesthesiologist must learn about this at least some time in their education about this...

i need to ask you ,guys...if i want to transport my patient from a quiet remote location to my hospital and it was far away...i need to provide adequate oxygen supplies (oxygen cylinders) to bring with me..i know how to calculate it if we use the flowmeter (L/min)...but how about if i am using a ventilator ? what is the formula? thx u

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[ssmallz]

quick and dirty method - PSI/3 = # of liters left, then figure out how many minutes you have by dividing by the # of liters/min.

Ex. 1800 psi = 600L = 300 minutes @ 2L/min.

It's not perfectly precise but it works well enough in clinical practice

 

[btbam]

It's cross multiplying iirc. 660 L of o2 in a full tank at 2200 psi, so 660/2200 = x/psi showing. Then just
Calculate # of liters remaining at the current L/min.

 

[ketap]

hello, thx for the info guys...i get what you both mean...but, i am very sorry..but i am actually asking something different...

the formula u told me is for an oxygen device with flowmeter,isn't it? but i actually talking about how can i know how many oxygen tanks i should prepare if i am going to transport a patient with a ventilator? how can we calculate it?
many thanks in advance

best regards,Ketap

 

[Dejavu]

hello, thx for the info guys...i get what you both mean...but, i am very sorry..but i am actually asking something different...

the formula u told me is for an oxygen device with flowmeter,isn't it? but i actually talking about how can i know how many oxygen tanks i should prepare if i am going to transport a patient with a ventilator? how can we calculate it?
many thanks in advance

best regards,Ketap

I think you can still use the psi/3 formula. All you need to know is the O2 consumption of your ventilator. Then you do the math to see how fast your tank will be sucked dry.

I think that answers it, no?

 

[Stank811]

Well that is much more complicated because the ventilators use the O2 to drive the ventilator. I would check with the manufacturer of the ventilator you are using. I cant imagine there is a simple formula to use because it depends on so many variables.

 

[Stank811]

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2564216/

 

[geogil]

you could disconnect your macine from the wall for 15 minutes, run it off the cylinder in back and calculate the amount of consumption based off the aforementioned loss of pressure calculations. That way you'd know approximately how much your vent used in case you needed it. ALternatively, you could just hook an ambubag up to the ETT and then use your flowmeter and pressure gauges to estimate.
The E cylinder will last a heck of a lot longer that way, the vent uses A TON of gas. Also, you should know if your vent runs on air v. O2.

 

[jwk]

Y'all are assuming E-cylinders for your estimate of PSI/3. There are 1/2 a dozen other sizes in commercial use, and your formula doesn't work for any of them.

A full E cylinder holds 660 liters of O2. At it's simplest, 660/liters per minute flow = the number of minutes you have. An oxygen powered ventilator obviously has to be taken into account. Since E cylinders are in widespread clinical use, and are frequently found hanging on the backs of anesthesia machines, you should definitely know their approximate full volume and how PSI relates to the volume of gas remaining.

Ketap, your question is really pretty vague and a really poor hypothetical example. A "remote location" - "far away". Is that like far corner of the hospital, or far corner of the state? In-hospital transports are almost always done with an ambu bag connected to an O2 supply. So even at 15 liters per minute, you have more than 1/2 an hour of hand bagging before you need to worry.

But if you're transporting via ambulance, they will have the large supply tanks on board containing several thousand liters of O2, which renders discussions of E cylinders somewhat moot.

Now - on the chance that your O2 supply on your anesthesia machine suddenly craps out, unless you KNOW your ventilator is NOT oxygen driven, you need to manually ventilate your patient to conserve your supply.

 

[ketap]

hi,friends..thx for responding.....very very helpful respond..and great formula from the website..thx..
sorry,because i didn't reply it earlier..it is quiet hard nowadays to connect to the internet because of the bad weather in my country..
btw..regarding JWK question: well ,what i meant with "remote area" and "far away" is to go to another province of my country..and sometime i need to transport my patient with a ventilator by air ( helicopter or private jet)... i am sorry because i didn't mention about this in my early post...
my problem is that : every time i need to evacuate a patient with a ventilator, before i go,i must make sure that i bring sufficient amount of oxygen cylinder tanks but not too many so that it will be too heavy for the plane to bring it with them..now,how can i know how many tanks should i bring with me ?as you have said before..i know also that ventilator will take way too many oxygen compare to bagging with an ambu bag..i still can't find the answer...

best regards,Ketap
oh ya,happy new year,friends

 

[jwk]

hi,friends..thx for responding.....very very helpful respond..and great formula from the website..thx..
sorry,because i didn't reply it earlier..it is quiet hard nowadays to connect to the internet because of the bad weather in my country..
btw..regarding JWK question: well ,what i meant with "remote area" and "far away" is to go to another province of my country..and sometime i need to transport my patient with a ventilator by air ( helicopter or private jet)... i am sorry because i didn't mention about this in my early post...
my problem is that : every time i need to evacuate a patient with a ventilator, before i go,i must make sure that i bring sufficient amount of oxygen cylinder tanks but not too many so that it will be too heavy for the plane to bring it with them..now,how can i know how many tanks should i bring with me ?as you have said before..i know also that ventilator will take way too many oxygen compare to bagging with an ambu bag..i still can't find the answer...

best regards,Ketap
oh ya,happy new year,friends

You'll have to find out from the manufacturer of your ventilator what the oxygen requirement is for powering the vent itself. Maybe it's 20 liters per minute - maybe more, I have no idea. Then make sure you know what size your O2 tank is and how many liters are in a full tank (660 liters for an E cylinder). Then it's all just simple math. Add the liters per minute required to power the vent plus liters per minute for the patient. Divide that into 660 and you'll have how many minutes each tank will last. Then figure out your trip time, add a reserve factor, and you got it.

 

[ketap]

thx..jwk .very nice explanation..i'll start searching the ventilator manual then, thanks but what is the reserve factor? thx u again

 

[jwk]

thx..jwk .very nice explanation..i'll start searching the ventilator manual then, thanks but what is the reserve factor? thx u again

You should plan for the unexpected. Take more than you think you'll need.

 

[ketap]

jwk:thx a lot!!