Running out of o2
- Thread starter joeboo
- Start date
There is no real formula. There are too many variables. What is the flow rate? What is the patients' tidal volume? What device are you using to deliver O2? What is the temprature?
There are charts that will give you an estimate usually based on 4lpm and 12lpm.
Realistically, you need to plan ahead. If you know you have a long distance transport then it might be prudent to find out how your patient needs oxygen. A nasal cannula will last longer than a NRB.
We carry 3 - 6 D tanks and 1 - 2 M tanks on our rigs.
There are charts that will give you an estimate usually based on 4lpm and 12lpm.
Realistically, you need to plan ahead. If you know you have a long distance transport then it might be prudent to find out how your patient needs oxygen. A nasal cannula will last longer than a NRB.
We carry 3 - 6 D tanks and 1 - 2 M tanks on our rigs.
NomadicMedic
I know a guy who knows a guy.
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Of course there's a formula.
You first have to know the constant of the tank.
D cylinder 0.16
E cylinder 0.28
M cylinder 1.56
H cylinder 3.14
Take the constant multiplied by the tank PSI-200 (for safe residual pressure) divided by the flow rate.
For example, 0.16*2000-200/10.
A full D tank with 2000 psi will last 28 minutes if you're flowing 10lpm, leaving you 200psi in the tank.
Make sense?
You first have to know the constant of the tank.
D cylinder 0.16
E cylinder 0.28
M cylinder 1.56
H cylinder 3.14
Take the constant multiplied by the tank PSI-200 (for safe residual pressure) divided by the flow rate.
For example, 0.16*2000-200/10.
A full D tank with 2000 psi will last 28 minutes if you're flowing 10lpm, leaving you 200psi in the tank.
Make sense?
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Glad I refreshed the page before I typed all that 
Aidey
Community Leader Emeritus
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Why would their tidal volume affect how long the O2 tank is going to last? The oxygen is delivered at a set rate, it isn't a demand valve. Same thing with the delivery device. A nasal cannula at 6lpm is going to use exactly as much oxygen as a SVN at 6lpm.
NomadicMedic
I know a guy who knows a guy.
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Me too. I remember learning this in EMT class. We were tested on it too.
Here's some practice:
http://emtsstudentpage.com/o2_tank_math.htm
I remember learning this in EMT class. We were tested on it too.Here's some practice:
http://emtsstudentpage.com/o2_tank_math.htm
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ThadeusJ
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The tidal volume would affect the cylinder life if you're working with a demand valve type device. Use the equation as stated by n7lxi. Remember that different cylinder sizes have different constants and not all "D" are created equal (i.e. the Super D, which I believe is similar in size as an E).
Read the tags on the cylinders as it should tell you what the full volume is in litres. This is useful if you ever change cylinders for metal to the carbon fibre types, which hold a considerable amount more.
I also made up a chart that some find useful. I colour coded the various cells as the cylinder life approaches 30 minutes or less, with a residual of 200 psi.
Read the tags on the cylinders as it should tell you what the full volume is in litres. This is useful if you ever change cylinders for metal to the carbon fibre types, which hold a considerable amount more.
I also made up a chart that some find useful. I colour coded the various cells as the cylinder life approaches 30 minutes or less, with a residual of 200 psi.
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There are many different devices that use oxygen including a demand valve. The OP didn't state that they were only using a NRB or NC.
After I posted I realized exactly what the OP was talking about and was going to post what n7lxi posted. Unfortunately I wasn't home to do so. Thats the last time I post when I'm tired.
Aidey
Community Leader Emeritus
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Name a demand valve delivery device that is found on an ambulance that is not part of a nitronox system or ventilator.
abckidsmom
Dances with Patients
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DesertMedic66
Forum Troll
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My airpack. But that delivers air.
And it's also yours, not the patients lol
JPINFV
Gadfly
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An independent BiPAP is psuedoish demand valve due to the increased pressure on inspiration.
Aidey
Community Leader Emeritus
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JPINFV
Gadfly
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Oh.. and OP... smart phone and the Clinicalc app. It's also useful for the pregnancy wheel app.
Meursault
Organic Mechanic
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We don't need some weird ad hoc equation or an app; the ideal gas law should be good enough to estimate. Look at the cylinder label, which gives the capacity of the tank at full pressure (usually 2000 psi) and make some simple assumptions. Given constant volume, temperature, and ideal behavior, all reasonable assumptions, pressure and amount of oxygen remaining are directly proportional. For example, 1000 psi means half the capacity of the tank in liters delivered (actually in moles, but given our assumptions). From there, just divide by flow rate in L/minute.
To recap: find amount of oxygen (liters delivered) in full tank at filling pressure (on label), divide by current pressure/filling pressure to give current amount of oxygen, divide by liters/minute.
Looking at the "weird ad hoc equation" again, it appears to just slightly disguise the full volume of each tank size with a conversion factor in L/psi. Not really elegant or flexible.
To recap: find amount of oxygen (liters delivered) in full tank at filling pressure (on label), divide by current pressure/filling pressure to give current amount of oxygen, divide by liters/minute.
Looking at the "weird ad hoc equation" again, it appears to just slightly disguise the full volume of each tank size with a conversion factor in L/psi. Not really elegant or flexible.
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Like it's been point out, unless you're using a demand valve it's a fixed flow rate.
Using a vent would be a different formula but it's still not difficult to figure out how much time you have.
OP how much O2 do you carry and how long was this transport? We carry an onboard M cylinder, a D cylinder in our bag and 4 spare D cylinders. I've never even come close to running out of O2. Burned my whole M cylinder in a shift but still had plenty of O2 in the portables and the VSTs brought me a new onboard tank but that's not a luxury everyone has.
Bullets
Forum Knucklehead
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I said found on an ambulance, not a museum.
We still carry them...:sad:
The fire department likes them for rehab for whatever God forsaken reason
rwik123
Forum Asst. Chief
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They are still in your protocols?