Posts Tagged ‘oxygen’

We were challenged with transporting a patient 287 kilometers point A to B. The foreign doctor joining us asked one of the smartest question I’ve heard. And it’s the first question they asked to us.

“Will the oxygen last during the transport?”

My answer?

First I’ll give an overview on how to check or compute if your oxygen tank/cylinder can last  during a transport.


Giving of oxygen to victims or patients is considered a medication in pre-hospital settings. Oxygenation is an essential part of patient assessment especially for those who are undergoing hypoxia (lack of oxygen in the body).

“Never withhold oxygen from any patient who may benefit from it, especially if you must assist ventilation.”


Getting straight to the point, here is the formula:

(remaining psi – 200 psi)  x  cylinder size constant
________________________________________    =    duration in minutes
liters per minute

For those who cannot understand the formula, here it is in layman’s term. Get the remaining PSI (pounds per square inch) – you may check on it on the gauge of the tank’s regulator – then subtract 200 PSI from it…

Why? 200 PSI is your ‘safe residual volume’.
What? When you have consumed the remaining length in minutes (answer to the formula) you will still have a remaining 200 PSI in your tank to work with, whether to change the tank or get to your destination.

…The answer to your PSI will be multiplied by a constant number depending on the size of the oxygen tank/cylinder. You may see the size of the tank embossed or engraved on the tank just below the valves…

Below are the constant numbers for each size.

D = 0.16
E = 0.28
M = 1.56
G = 2.41
A,H,K = 3.14

Troubleshooting for sizes

If you are not sure of the size of the tank, find time to ask your manufacturer or where you get your refill how much oxygen the tank is filled. Below are the sizes and amount of oxygen inside the tank.

D = 350 Liters
Super D = 500 Liters
E = 625 Liters
M = 3,500 Liters
G = 5,300 Liters
A,H,K = 6,900 Liters

…(Review: subtract 200 from your remaining psi then the answer is multiplied by the constant) The answer will be divided by the amount of oxygen that will be given to the patient…

…The final answer to all these process is the duration the tank will last in minutes. To convert it to hours, simply divide the final answer by 60 minutes.

That’s how simple it is.

Going back, my answer to the doctor?

I was checking the remaining PSI (1600) and assumed the smallest of the big tanks as the size, thus M, and we will be giving the patient 4 LPM of oxygen during the transport. Then quickly computed and got around 8.5 hours (i even subtracted 300 as my safe residual volume just to make sure). The travel will last for about 6-7 hours. Will the tank last?

I told the doctor, “Yes the oxygen tank can accommodate the transport and we still have a spare one if anything goes wrong.”

Source: AAOS Emergency Care and Transport of the Sick and Injured


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