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Change in flow rate - what's going on?
#11
RE: Change in flow rate - what's going on?
Knightfire - There are definitely allergy issues here but they don't seem to be bothering me too badly at the moment, at least in terms of congestion and so forth.

Geer1 - I tried using the machine last night while awake.  I usually have it set to ramp up and never really feel my actual sleep pressure, but it was interesting to do so last night.  I noticed that it felt like I was never able to get a 100% full exhale.  It felt like the pressure of the machine kicked back in and stopped my exhalation when I was like 70% through with breathing out.  It felt like it really threw my breathing cadence off and after a while it made me feel almost like I was hyperventilating.  

I added a pdf report of last night's sleep (after I had the hyperventilating feeling I didn't use the cpap until I woke up later and then I put it on) and two close-ups of flow rate charts.


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#12
RE: Change in flow rate - what's going on?
Post full OSCAR screen shots so we can see the stats on left side and main charts (flow rate, pressure, flow limitations, leak rate).

In this case I want to see a similar zoom shot of the area you believe was the issue with machine forcing you to breath but showing both flow rate and mask pressure.

I am pretty sure the dreamstation does not force you to breath. I am not fully aware of how it reacts to the cardiogenic oscillations and seeing flow rate on top of mask pressure will help decipher that.

Hyperventilation and trouble exhaling can both be caused by plugged vents or plugged air filter. If your mask needs cleaning clean it. If you haven't changed air filter recently do so and change on a semi regular basis (I'd say 3 months). I learned both those lessons the hard way.
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#13
RE: Change in flow rate - what's going on?
You may have two filters, a reusable one that you should replace at least every six months, and a finer, disposable one, which you should replace at least once a month.
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#14
RE: Change in flow rate - what's going on?
Pictures added of the full night and also a zoomed-in screenshot of where I was awake and felt like I was struggling to fully exhale.

I'm using dreamstation headgear (nasal pillow) and I could tell it was operating okay (not plugged) from the little vent upfront and on top.  I also just changed the filter a couple of days ago on the machine and the issue was occurring before and after.  

It felt more like the EPR would stop and put the pressure back up before I was done breathing out.  So I'd get 70% done with a breath and the machine would be like "okay, he's done, let's fire back up".  So I'd be trying to exhale the last 30% (which isn't a strong exhalation) and the machine would be ramping back up to full pressure making it impossible to get the rest of the air out without unnaturally forcing it. I do have a dreamstation as well, so I may go back to trying that at a lower pressure to see how it feels vs the ResMed.


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#15
RE: Change in flow rate - what's going on?
Ah, so it wasn't forcing you to breathe so much, as just cutting the pressure relief off at a point that feels too soon for you? That makes more sense, I'm not sure at what point in the breath it does that compared to the equivalent on the Dreamstation, honestly...

But I have a question... Your profile says you have a Philips Dreamstation but your charts say Resmed 10 Autoset. Are you using both? Sorry if I missed this.

Edit to add: I'm not seeing any EPAP data line on the pressure chart. I see you have it set up to use EPR of 3 and pressure of 6-7. That means that you can only make use of an EPR of 2 at pressure of 6, and EPR 3 at 7, but most of the time, you're below 7... I don't know how the EPR works with Resmed - does it just give you as much EPR as it can, down to the minimum of 4, or does it do nothing if it can't give the full EPR value? Though at a pressure of 4 I feel like I can't get enough air, so that would make ME hyperventilate... so I'm not sure. Maybe I'm just missing something?


See my comparison of Viatom/Wellue and CMS50F oximeters here.

Not a doctor, definitely not your doctor, all advice is given as-is and represents simply my own understanding as a fellow patient and OSCAR user.
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#16
RE: Change in flow rate - what's going on?
Yeah, it just feels like my natural breath doesn't sync up with the ResMed's interpretation of how I breathe.  I'm still exhaling and it's gearing me up to inhale.  

I started out with a Dreamstation and went to the ResMed based on reviews and advice on the forum.  I haven't used the Dreamstation in a while but I don't feel like it did the change in pressure quite as dramatically as the ResMed.
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#17
RE: Change in flow rate - what's going on?
Resmed's absolute minimum pressure is 4 cm. This means that any EPR setting that would produce a pressure lower than 4 cm will be set to 4 cm. If you set your pressure range to 4 to 7 cm and an EPR of 3, the EPAP pressure will always be 4 cm.
Crimson Nape
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#18
RE: Change in flow rate - what's going on?
Something doesn't seem quite right (pressure graph not displaying properly). Post the "Mask Pressure" graph instead of "Pressure".

One of the obvious changes to make is to shut off ramp. Especially at these low pressures there is no reason to use ramp. With your ramp set at 4 cm then there would be no EPR available until ramp period finishes. In short your pressure should not have been changing at all during those periods. What I still think might have been happening is lack of EPR and dirty filters/vents etc causing you not to breath effectively causing high CO2 and then hyperventilation. The seeming difference in pressure may have been due to your inhale sucking in air faster then the machine would supply it (due to dirty air filter). Been there, done that, it can happen.

EPR on an autoset doesn't stop. During exhalation the pressure drops fairly quickly down to EPAP. The pressure only starts to raise after you initiate inhalation and it will only continue to rise if you continue inhalation, if you stop inhalation and start exhaling again the pressure supply drops quickly and cycle restarts. With some other machines (like bilevels with tmin, a setting that maintains IPAP for a minimum amount of time) cardiogenic oscillations can cause a premature rise and hold of pressure (due to cardiogenic oscillation making machine think you are starting inhalation process) but that simply cannot, nor does not happen with an autoset.
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#19
RE: Change in flow rate - what's going on?
If that doesn't fix it, I would maybe try raising the min pressure a little to see if that reduces the hypercapnia too, by increasing the airflow. I know I feel uncomfortable for any time below about 7 or 8. But yeah, definitely try without ramp, too.


See my comparison of Viatom/Wellue and CMS50F oximeters here.

Not a doctor, definitely not your doctor, all advice is given as-is and represents simply my own understanding as a fellow patient and OSCAR user.
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#20
RE: Change in flow rate - what's going on?
One thing that I do is that I never set a totally fixed pressure, but instead a min and max close together. For example right now I'm trying to see how my flow limits interact with the pressure settings and I'm set at min=7, max=8, EPR=3. Being able to see whether the machine is bumping pressure up or down is useful in figuring out what I'm looking at. (Or at least seeing what the machine thinks it's looking at!) It helps me to figure out when a zero flow limit is real or not -- when I've got a zero but the machine is still pegged at 8, I know that it's reacting to something else and probably not even calculating the flow limit.
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