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Is my cpap working?
08-15-2013, 10:35 AM
I have a Phillips Respironics REMstar Pro C-Flex +. I don't know if it's working. To test it, I purposely stopped breathing during the inhale and the pressure immediately stops. I've done this numerous times to test it and it does it each time. So I'm assuming that if I do stop breathing, the cpap machine isn't going to be doing what it's supposed to be doing. I'm new to using a cpap machine. I've been using it for about 4 months now. Can someone help me with this? Is this thing working or have I been wasting my time with it?
08-15-2013, 11:11 AM
You are probably thinking of what is called an auto servo machine.
Fundamentally, a CPAP unit make sure that your airway is pressurized to a level higher than ambient. The intent is that the airway pressure serves as a splint to keep the soft palate from collapsing and blocking your airway. Various factors will determine how much pressure is required to accomplish this (lying on your back vs your side is a big one), and a sleep study titration is designed to determine what this level should be.
Now, while older machines provided a constant pressure, newer machines incorporate comfort features like EPR (for ResMed machines) and CFlex/AFlex/BiFlex (for PRS1 machines). Since apnea events do not occur while you are exhaling, the machine can try to make you more comfortable by lowering the pressure as you exhale.
So you can see that your machine is not designed to react when you have stopped breathing. It is designed to make sure you never stop breathing in the first place. If you intentionally stop breathing, or if your treatment pressure is set too low and your airway collapses anyway, there's nothing more that your machine can do.
An auto servo machine typically is set for a large range between inhale pressure and exhale pressure, say 10 cmH2O for exhale and 20 cmH2O for inhale. It also has a watchdog backup that instigates the higher inhale pressure if it does not detect an inhale after a certain timed period. However, these machines are designed for patients with what is called "Central Apnea". Unlike "Obstructive Apnea", which is caused by physical blockage of the airway, "Central Apnea" is caused by the brain simply "forgetting" to breathe. With obstructive apnea, there is a breathing effort made (ie. diaphragm movement, chest/abdominal expansion, etc). With central apnea, there is no effort made.
There is also an auto-CPAP machine. This type of machine dynamically adjusts your treatment pressure through the night to attempt to provide only the minimum pressure required to keep your airway open. Based on airflow sensors, if it detects that your airway is starting to collapse, it will increase the treatment pressure to head off any upcoming blockage. If it detects that your airway is solidly open, it will try reducing the pressure to see if a lower treatment pressure also continues to keep your airway open.
And, just to finish off the discussion of machine types, there is also Bi-level CPAP machines. These are very much like regular CPAP machines with EPR/CFlex, except that EPR/CFlex is limited to a maximum pressure difference of 3 cmH2O between inhale and exhale. A Bi-level CPAP machine has separately settable inhale and exhale pressures that can be significantly different (eg. 10 cmH2O). As well, Bi-level CPAP machines can typically provide pressures up to 25 or even 30 cmH2O, where non-Bi-level CPAP machines typically can only provide up to 20 cmH2O pressure.
08-15-2013, 11:43 AM
Wow, thanks Ron. You were pretty thorough in your answer. One more question. On the setup screen, next to c-flex, it has the number 2. I'm assuming that's the pressure? And does that seem right? And should I increase it? And if so, how do I increase it? My manual is very vague and doesn't really explain too much.
Yes, your CFlex value is the pressure relief provided during exhale. It is measured in cmH2O, the same units as your treatment pressure is measured in. So, if you have a CPAP treatment pressure of 8 and a CFlex value of 2, your pressure will vary between 6 during exhale and 8 during inhale.
As I mentioned, for most people, this is a pure comfort setting. I recently went through an exercise myself where I spent a week at each of the 4 different CFlex (actually AFlex, since I have the auto-CPAP unit) settings (1, 2, 3, and off) and didn't see any significant change in my treatment profile. So I set it back to 3 and have left it since.
Assuming your machine provider has not locked the CFlex setting, you can simply go into the CFlex menu option (the top left square in the main menu) and select whether you want 1, 2, or 3. I believe there is also a CFlex Demo setting that, if you change it, it will temporarily turn on the machine with that CFlex value so you can be wearing the mask and immediately feel the difference as you change the settings.
To turn CFlex off, or to unlock the CFlex settings if it has been locked, you will need to go into the clinician's menu. This is the same menu that the treatment pressure is set in, so do be aware of what you are doing in that menu. You get to that menu by turning the dial to the Settings menu but pressing both the knob button AND the ramp button and holding them for 5 seconds or so. Then release the buttons, go to the Settings option and press the knob button to go into the menu.
As to whether a setting of 2 is "good" or whether you "should" change it, only you can answer that. Is the paint colour in my bedroom "good" or "should" I change it? It's personal preference. My only recommendation is to only reduce the CFlex settings by one at a time and to spend several days at the new setting to become accustomed to it.
08-15-2013, 01:30 PM
Hi Sleepless Nights,
WELCOME! to the forum.!
I can't add anything to the great advice you hav already gotten.
So hang in there for more responses to your post and best of luck to you with CPAP therapy.
08-15-2013, 11:50 PM
Quote:So you can see that your machine is not designed to react when you have stopped breathing. It is designed to make sure you never stop breathing in the first place. If you intentionally stop breathing, or if your treatment pressure is set too low and your airway collapses anyway, there's nothing more that your machine can do.
If I am understanding you, this statement is incorrect.
While the goal of the machine is to indeed keep the airway from closing in the first place, it is not incapable of re-opening the airway. With my S9 Autoset, if I purposely stop breathing, I feel the air pulse almost immediately. I have assumed this is it testing to see if it is a blockage (obstructive) or open airway (central). If I am still holding my breath, it will begin to slowly increase in pressure. I've not held my breath long enough to see how high it goes but it does increase.
Quote:My manual is very vague and doesn't really explain too much.
Then you are in luck because here is where you can get the clinician manual which explains much more.
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08-16-2013, 02:32 PM
(08-15-2013, 11:50 PM)PaulaO2 Wrote: If I am understanding you, this statement is incorrect.
You are, but we are both correct. The OP (to whom I was replying) only has a fixed-pressure CPAP machine. An auto-CPAP machine does, as you say, increase pressure given an apnea event. However, as you also say, it does take a significant period of time, so it would be stretching things to say that even an auto-CPAP machine is designed to fix a particular apnea event.
Auto servo CPAP machines, on the other hand, respond quickly enough that they will fix individual apnea events.
(08-16-2013, 02:32 PM)RonWessels Wrote:(08-15-2013, 11:50 PM)PaulaO2 Wrote: If I am understanding you, this statement is incorrect.
The period of time to raise pressure varies even among auto-CPAP machines. There is a very informative post about this on another forum by the member 'robysue.' I'm not sure if I should link to it.
The way that I read the author's explanation, it sounds like the S9 AutoSet does not try to establish a baseline treatment pressure within the set range. It raises pressure rather sharply up to the set maximum in order to prevent further events. Once it's satisfied with the flow, then it lets the pressure slowly fall back down, going all the way to the set minimum if it can safely do so. This is why the S9 pressure graphs look like "waves" with sharp fronts and more gentle backsides.
The PRS1 Auto takes a more calculative approach to raising and lowering pressure and it does hunt for a baseline. That means that early on when events start happening, it is more likely to let a few get by but once the baseline treatment pressure is established and the machine is satisfied with the results, it is less likely to reduce the pressure much. It tries to do so periodically while testing the flow for degradation, but will revert to the previously established baseline if it detects something. This is why the PRS1 Auto pressure graphs look more sawtooth in appearance, with periods of flat lines.
My personal feeling about it is that if you want to establish a baseline treatment pressure (to self-titrate or figure out an ideal CPAP pressure) then using a PRS1 Auto is perhaps better because it does the work for you in finding that 'magic' pressure. If you want to leave it up to the machine (auto mode), then perhaps the pressure swings of the S9 AutoSet are better since it reacts more quickly to prevent as many events as possible and perhaps keeps you more comfortable at lower pressures for a larger percentage of time. It's a little harder to judge baseline pressures from an S9 AutoSet graph, but not impossible.
08-16-2013, 04:13 PM
(08-15-2013, 11:43 AM)Sleepless Nights Wrote: Wow, thanks Ron. You were pretty thorough in your answer. One more question. On the setup screen, next to c-flex, it has the number 2. I'm assuming that's the pressure? And does that seem right? And should I increase it? And if so, how do I increase it? My manual is very vague and doesn't really explain too much.
I have the same machine and thankfully they explained that feature to me when I got mine. The demo mode is kind of nice to try out and compare the difference each mode makes (basically sit there for a bit and try each one a few times). I started out on one but was struggling with staying asleep and getting used to the machine. After trying each setting a bit I set my C Flex to 3. Ron is dead on in saying that this is a personal preference. This feature basically makes it easier to exhale (so depending on what pressure they have you set at, you may or may not need it... not to mention everyone has a different idea of what is comfortable); 3 is the maximum setting to help make exhaling as comfortable (or easy) as it can.
Hope that helps a little.... I'm learning too..
08-16-2013, 06:08 PM
WELCOME! to the forum.!
Best of luck with CPAP therapy.
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