Help to validate my understanding of the basics of CPAP

[Albatros]

I would like help in understanding the basics of CPAP

What I think I understand:
With a Resmed Airsense11 machine, the machine sends air into my airways according to a pressure that will evolve between Min and Max pressure in order to prevent or correct a closure (OA or H).

The Flow Limitations  announce an OA/H. Even if the OA/H can happen with FL =0
In general when FL increases, the pressure increases to stop the aggravation of the limitation.

There is an inhalation pressure Ipap and an exhalation pressure Epap. By adjusting EPR I decrease the pressure during expiration Epap. This is for comfort.
If Epr = 1 Epap = Ipap -1

When I  am not to sure:
The important thing is the Ipap pressure because it opens the airways.
Epap pressure has no role vs OA/H ?

When I start not to understand :
if we do +1 on EPR, we should do +1 on min pressure to keep Epap constant?  Why ?

What I don't understand at all, when I read in the Apnea Therapy optimization:

 "It is the exhale pressure that needs to be elevated to prevent Obstructive Apnea (OA), and it is the pressure differential between inhale and exhale that helps relieve hypopnea."

"A good rule of thumb is to keep your minimum pressure setting about 2-cm below your 90% pressure or near the average if they are close. The goal is to raise support (Min Pressure / IPAP) to reduce/minimize/if we are lucky, eliminate Obstructive events. These include Hyponeas, Flow Limits, and Snores. The Max Pressure / EPAP is lowered to minimize other issues (Aerophagia , swallow too much air, too much pressure causes wakeups) if needed. Typically it is set at either MAX pressure (20 cmH2O) or just above the max pressure to prevent wild running high.

Thank you

 

[Crimson Nape]

You are off to a good start in your understanding.  You need some minor tweaking on some things.

When I  am not to sure:
The important thing is the Ipap pressure because it opens the airways.
Epap pressure has no role vs OA/H ?

It is the EPAP pressure that maintains an open airway when you exhale.  This is when the airway normally collapses, causing the OAs and Hypopneas.  Also, increasing your EPAP pressure a little above your required pressure, can help increase your tidal volume, too.

The IPAP pressure helps eliminate any resistance when you inhale.  Resistance will show up in your flow rate waveform as a cursive "r". (My best verbal description.)

Using a pressure differential (bi-level) is like a double-edged sword. On one side, it reduces or eliminates the flow restrictions.  The other side is it can increase CAs.  This is due to both the body's reaction to having a blast of air blown in your face, and the process of CO₂ washout.

Another item to consider is the Resmed uses the flow limit as a determination to increase pressure.  If you are on a standard CPAP, like your AS11, and you are unable to sufficiently reduce flow limitations, then the CPAP will keep increasing in pressure to where either the flow limitation is eliminated or the CPAP reaches it maximum set pressure.  This is a good reason to restrict the maximum pressure.

- Red

[Albatros]

Thank you

If I understand you correctly: the IPAP helps open the airway vs the FL. The EPAP maintains/keeps the airway open.
So both are playing a role/ IPAO opens the airway and EPAP maintains it open.

Is that correct ?

Concerning the EPR:
why if I do EPR = 1 should I do Min Pressure = +1 ?

[Gideon]

Officially on a CPAP there is no differential pressure between inhale and exhale so
Pressure= IPAP = EPAP

Therapeutically EPR doe make a difference.

Technically you should adjust pressure when pressure is increased or decreased.
Practically you typically don't need to because the user is titrated to a higher pressure then they need. If needed we will adjust pressure after application of EPR.

Titration 101.
Establish pressure (exhale) that resolves OA events.
Then increase the differential pressure while maintaining exhale pressure by increasing the inhale pressure to manage hypopneas, RERAS, and flow limitations.

[Crimson Nape]

Albatros -
If you have found that a pressure of (let's say) 10 cm is working for you, then if you add an EPR of 1 to this, it reduces your EPAP pressure by one, thus making your pressure now 9 cm. In order to return to the pressure of 10 cm for the EPAP pressure, you will need to increase the pressure setting to 11. On a Resmed CPAP, the EPR will be subtracted from the pressure setting. The rule is, whatever EPR value is used (1-3), you need to adjust your pressure setting by the same value in order to maintain the EPAP pressure to the desired level. Think of the EPR value as a negative number.

- Red

[Albatros]

Thank you  because I am making progress!

To fight the OA's, the KEY parameter seems to be the EPAP pressure  (not the Inhale Pressure).

Then, when on my Resmesd Airsense 11, if I set Min Pressure =10, because Med Pressure = 12, I am, in fact, setting EPAP =10.

If, then, for some reason, I set EPR =2, then EPAP = 8. Not strong enough and I should increase Min Pressure + 2, so Epap = 10.

Correct ?

Then why , should I use the EPR, if I do not have exhalation problem ?
Why is it useful ? 
What impacts does it have on the other datas on my Oscar ?

[Crimson Nape]

Using EPR will help eliminate flow limitations. This will reduce pressure changes.

Why not try it and see what happens.

- Red