O2 tank duration? Size M Patient on continuous 15l.

Grant Brown

Forum Ride Along
Had an interesting call for pt transfer the other day. Local nursing home ask if we could transport a pt from nursing home to DR appt in town 70ish miles away. The intersting part was finding out pt was on 15l o2 all the time. I finally found a number for how much one of our M size tanks holds in liters. 3,000l
but the closest conversion i could find was for a tank holding 3741l. I cut that down to 75% to get closer to 3000l and the conversion gave me just under 3 hrs worth of oxygen. That wasnt giving me much of a cushion 70 miles both ways = 140 miles Usually 1 1/2 hrs to get there one way so thats 3 hrs already. The nursing home said there tanks which are E series would only last 15 min so i could take a cple of them along with our D series on rig to cover the gap but then i had to figure out how to strap them in and where.

Some ideas i had was :

Pts on 2 concentraters that are tied together to get pt to the 15l at the nursing home so I thought we could take one along since i have 120 in the rig and use it to be able turn the oxygen use from rig down. That might have got us some more time.

Taking the pts BiPAP with us to see if that would help limit o2 use from the rig??

Before the transfer got cancelled on us i had decided i was going to strap another M series main tank to ours so that we would have little over 5 hours of o2 and switch all our Ds in the rig out with Jumbo Ds that we have to gain more time.

My question is if anyone else has ran into a long distance transfer with pt on continuous high flow oxygen and how did you manage it?


Family Guy
Yes. There are apps for O2 calculations that are helpful for situations just like the one you encountered.


Non flying critical care flight attendant
There are constants that you memorize. A D tank, usually the one on the back of the gurney, is 0.16. An M tank, usually the ambulance main tank is 1.56.

The math is...

((PSI - 200) x constant)/liters per minute = minutes you have until tanks are empty

The reason 200 is subtracted is margin of error. The tanks also will not flow at certain rates depending how empty it is. You might still have some oxygen left in the tank, but because it doesn't have a meet a minimum pressure, it won't flow at that rate anymore.


Forum Deputy Chief
Also; you are better off putting a tank on the floor between the cot and wall, and strapping it to the cot braces. Unless you have enough room to secure multiple tanks in the compartment where the M tank already is.
We used to transport a patient to a VA appointment a couple of times a month about 150 miles each way. That was Vent Dependent and the vent ran on 25 L/m. At 1st we had someone driving a pickup with multiple tanks strapped in a rack on it, that was fun to switch on out. We got pretty fast at it.
Then we started storing extra tanks at a couple of Fire Stations, that were on the way: after we bought a used truck that we could strap 3 tanks in the same compartment: We just had to stop and switch the regulator from tank to tank.


Forum Deputy Chief
The M-T tanks are the worst for oxygen delivery.


Community Leader


Community Leader
There is an online version of the calculator that can help with this. http://www-users.med.cornell.edu/~spon/picu/calc/o2tankd.htm

You choose the tank size, your flow rate, your "safe residual" and either how long you need it to run or how much pressure is in the tank. Then the calculator will tell you how much pressure you need to run as long as you need it or how long the tank will last from a given starting pressure. This calculator does NOT have all the sizes. It doesn't have Jumbo D tanks for instance. Remember that often our tanks are considered "full" at 2000 psi, so if you do a calculation for the PSI you need and it's >2000, you need an additional tank or more.