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O2 remaining in e-cylinder calculator |
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Example
You are transporting your patient, who has emphysema, from your unit to radiology for a CT scan. Without oxygen at 6 L/min, your patient's O2 saturation on room air drops to 75%. It will take you 10 minutes to get there and back. The portable O2 tank you grabbed has 500 psi left in it. Do you have enough oxygen left for the trip? See the example below
At 500 psi with a flow rate of 6 liters per min, there are 28 minutes of oxygen left. Yes, there is enough for the trip.
Formula
My text book uses the following formula and data:
capacity (in L) / service pressure (in psi) = remaining contents (in L) / gauge pressure (in psi)
The service capacity for an e-cylinder carrying oxygen is 1900 psi.
The volume of oxygen in an e-cylinder is 660 liters.
Now entering the values listed above:
660 L / 1900 psi = remaining contents (in L) / gauge pressure (in psi)
I find it easier to look at this formula this way:
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0.35 x psi on gauge |
The 0.35 comes from dividing 660 by 1900.
In the example above:
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0.35 x 500 psi |
= 28 min |
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