How is Oxygen added

I had a question deleted on another forum about the adition of O2 to Xpap.
I simply cannot understand the physics involved and hope some of our technical types will help.
I understand that O2 from an O2 concentrator is connected to the output side and is added.
How is the pressure compensated for?
Some answered it was the Burnelli or venturi principle, but this CANNOt work on the output side because it has positive pressure.
For example, if a Xpap has a pressure of 12, then the concentrator MUST have a greater pressure to overcome the PAP.
How is the pressure compensated for?If additional pressure comes from the concentrator, then why does this not increase the pressure by the amt needed?
I wrote Invacare and they said cpap CANNOT be used with an oxygen concentrator.
HELP?

I was given a little T host connector. The oxygen goes in one branch
and the humid air flows in the other opening, and out the third opening.
Yes, I had the same questions as you do, but my Doctor said "You
ask too many questions. Just do it!". So I guess that the pressure is
strong enough coming from the Oxygen concentrator, that the Oxygen
either gets "forced" into the airflow from the CPAP, or else sucked in
and the air whooshes by. If I stop up the Oxygen inlet with my finger,
the pressure seems to build up until I take my finger off, and then the
Oxygen rushes out in force. I haven't yet had the confidence to see if
the rush of Oxygen can blow out my lighter, yet. Oh, yes. I actually
have used the PAP a couple of nights without the Oxygen turned on
(OOps!) and it seems to work just fine. The Oxygen also worked OK
with my PB 420e. I asked my Doctor if I really needed the Oxygen.
That just upset him! He apparently didn't like questions. So I had to
go out and purchase an Oximeter to see that I really didn't need the
Oxygen. When I told him this, he just got upset and sent an order to
the Home Care company telling them to turn it off. Of course, they
balked and wouldn't take it back. Apparently it is a nice lucrative
$600/month income for them. So now my fish are enjoying their super
oxygenated life in their aquarium. Such is life when working with DMEs,
and Sleep Doctors. Don't ask questions ... Just do it!

The oxygen source (compressed gas or concentrator) delivers the oxygen at a greater pressure than any cpap can deliver. So the oxygen flows nicely into the cpap circuit. The actual flow of oxygen into the cpap circuit can be set with the patient using the cpap at prescribed value if there is any doubt.

a reply:The oxygen source (compressed gas or concentrator) delivers the oxygen at a greater pressure than any cpap can deliver. So the oxygen flows nicely into the cpap circuit. The actual flow of oxygen into the cpap circuit can be set with the patient using the cpap at prescribed value if there is any doubt.
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Nice sounding words, but it does not in any way answer my question or explain how the pressure is compensated for.
If it is delivered to the output side by the T connector described by the previous poster, then what percentage of air delivered by the PAP and O2 concentrator?
If the O2 is the same pressure as the PAP, then it is a mixican standoff-- the equal pressures allow NO 02 to be added. If the o2 output is less than 12 cm, then air from the PAP will flow INTO the concentrator. If it is More, then the pressure is altered.
If the pressure increases above the 12 CM and allows O2 to come thru, then the pressure is increased and changes.

Why did Invacare say CPAP cannot be used with O2 concentrators?

Unless the PAP decreases the output to allow for the additional pressure from the O2 unit, then NO O2 can be added.

In any event, the prescribed amt of O2 cannot possibly be added unless it leaves the concentrator at precisely 12 cm and then the CPAP will be providing NO pressure.

The only way I can imagine the prescribes O2 being DELIVERED is for it to be attached to the input manifold- Where the air goes into the machine- where the filter is.
I cannot understand any possible way it would otherwise work.
Will someone pls run this by an engineer or at least a person with a basic understanding or the physics involved. BS not helpful.
To first poster: What did your O2 monitor actually show? more? less? same?

Gee, I don't understand the question well enough to answer it.

All I know is that I have oxygen added too. It is delivered by tube attached to an inlet to my humidifier, thereby added to the air forced through by my bipap. The oxygen machine is set at a level of 2 and the lady delivering it said I better not alter that. I obey most orders. But the oxygen brought my very low levels up to normal in just a few days, maybe sooner. I feel like a hospital patient and I have to sleep with that loud tapucketa tapucket sound, but I do what I'm told, most of the time.


Linda

The oxygen is delivered through a very small hose, maybe 20 to 40 times
less in diameter than the hose diameter for the PAP hose. Yes, of
course the pressure needs to be greater in the Oxygen hose, or else the
PAP air would force itself down the Oxygen hose. The Oxygen hose can
easily be used up to 75 feet away, whereas PAP hoses are usually less than
8 feet long. So yes, it will add pressure to the overall mix, but supposedly
not enough to greatly affect You asked what the Oximeter showed.
It showed me when I had periods of Oxygen desaturation during the night,
and how low the oxygen saturation got. Without PAP my desats got below
80%. With PAP they stayed above 95%.

Longer hoses have higher pressure losses.
Smaller diameter hoses have higher pressure losses due to friction.
Compare your house hose to a larger firehose. Not a huge difference
in diameter but a huge difference in performance.

My Oxygen generator talks about flows in Liters/second whereas PAP
pressure talks about cm of Water lifted.

1 ft H20 (foot of water) = 0.43352 PSI

From what I could find, the some regulators are set at 22psi or 4lpm. So, even if you are talking about 1 lpm of O2, you are still talking about a much higher pressure than cpap.

Pressure and volume really can't be compared in this case. My auto unit measures pressure at the mask. It seems like it would compensate automatically for any pressure added by O2. 4 LPM isnt much . The mask leaks much more than this. Something like .3 LPS. My guess is the O2 has lots of pressure behind the regulator and that keeps it flowing. Try turning a garden hose to a trickle. Put your finger over it. Sure you can hold it back a few seconds but eventually that 50 PSI at the main will blow you away.

2 Cents