Medicine course: first aid - too obvious?

[Function]

Hi everyone

 

An example question of my first aid theoretical exam in medicine is:

 

"Given an oxygen tank with a volume of 5 L, a pressure of 50 bar and a flow of 15 L/min. How many minutes could you use the tank?"

 

And so, 20 seconds, I'm not even going to explain how I got that answer, since it's too obvious -- is too obvious.

 

There must be more to it than only that... I mean, the pressure, I'm sure I need to do something with that. But what?

 

Can someone help me?

 

Thanks!

 

F

[Spyman]

To increase pressure in a 5 litres tank you need to press more than 5 litres of oxygen into it and when the pressure reach atmospheric pressure the remaining 5 litres won't flow out by itself.

[Function]

We're talking about a flask with 5 L of oxygen in it and a pressure of 50 bar, so they have to flow out. But for how long?

[DrP]

That 5L wont be 5L when it leaves the tank and gets to 1 bar though right? (As spyman has said) How many litres is it at 1 bar? What is the flow rate? Do the division.
Hope that helps.

[Function]

ahh.. reason to be ashamed now medicine is screwing all my formal scientific knowledge lol

 

It would be 250 L so @ a rate of 15 L/min, you'd have 16,67 min

[studiot]

Well my calculator made it 16.3 mins - say 15 mins for safety.

 

A 5L tank at 50 bar expands to 5x50 = 250 L at 1 bar.

 

Leave 5L in the tank as spyman said makes 245L available.

 

Using this at 15L/min is 245/15 = 16.333 mins.

Edited May 7, 2015 by studiot

[imatfaal]

As this is medicine do you have to think about the 12 12 rule? Very broad rule of thumb suggests that ventilation will require about 12 ml/kg (of body mass) 12 times a minute. No body needs 15litres of oxygen every minute. A healthy male at rest - ie not being ventilated or assisted will have a throughput of about 7-8 litres of AIR per minute

[Function]

Never heard of that rule (yet). Still in my first year and we're not to perform those things yet on our practical exam (however, we have to know these things for our theoretical exam; but not the 12-12-rule as you mention it; perhaps later)

 

Our practical exam only consists out of BLS yet. ALS (medication, manual defib, ...) is for later years

Edited May 7, 2015 by Function

[StringJunky]

As this is medicine do you have to think about the 12 12 rule? Very broad rule of thumb suggests that ventilation will require about 12 ml/kg (of body mass) 12 times a minute. No body needs 15litres of oxygen every minute. A healthy male at rest - ie not being ventilated or assisted will have a throughput of about 7-8 litres of AIR per minute

Everest climbers use a flow rate of about 3L/min. From what I've been reading about it they could get away with less flow if the delivery system could cope in those temperature and pressure conditions.

[studiot]

I don't know what the flow rates are for a hyperbaric chamber.