Is in-lab titration study needed for higher-risk patient who wants to avoid COVID?

[Crimson Nape]

CO₂ washout.
- Red

[DevinJones]

I'm new to CPAP/APAP, so all I know is that CO2 washout has something to do with the amount of carbon dioxide expelled through the CPAP mask.

Can you explain how this washout is related to the breathing flow-rate waveforms in my attachments? Thanks.

[Sleeprider]

I put this article in our wiki on respiratory drive that describes how central apnea can occur as a result of CO2 washout or more precisely a slight delay in the respiratory chemoreceptor feedback loop that controls our respiration by sensing CO2 and oxygen in the bloodstream and basic brain functions that control the pace and rate of breathing http://www.apneaboard.com/wiki/index.php...tory_Drive The wiki has links to the original article.

It's a bit advanced, but my best effort at explaining why many people seem to have central apnea in the absence of any apparent illness, injury, opiate use or other causes of CA. It's much more common than most people think, and your chart shows a typical pattern of alternating hyperventilation which drives off CO2 (hypocapnia) suppressing respiratory drive resulting in cessation of breathing which lets it rebuild (hypercapnia) and increase respiration. ASV works to maintain a steady minute vent rate that prevents these fluctuation in bloodstream micro-chemistry by using pressure support to increase respiratory volume when hypopnea or central apnea would otherwise occur, and allowing spontaneous breathing when that is not needed. In the end, respiration does not fluctuate and clusters of CA don't occur. The way that ASV works to level out breathing is explained in this Resmed Clinical Titration Guide starting on page 28. https://document.resmed.com/en-us/docume...er_eng.pdf

I'll start by directing you to the wiki, and ask you to come back with additional questions I'm sure you have.
ASV machines are available new and used, however a new device will more likely require a prescription.

[DevinJones]

Thanks very much for explaining it all and providing those links. I'm going to spend time reading all the information.

When you refer to my CSA events, do you see Cheyne-Stokes respiration in the waveforms?

[Sleeprider]

CSR tends to be on a longer interval and very gradual in the transitions. CSR is most often associated with heart failure and is working on a somewhat different mechanism than your periodic breathing and apnea.  I'll show an example of CSR in an Oscar chart, but understand we're talking about a condition that presents in a variety of ways.  In short, I don't see your chart as representative of CSR. Incidentally, Resmed does not see your condition as CSR either as it will put a CSR flag on the pattern.

[DevinJones]

Thank you.

I see waveforms in your OSCAR chart that sort of resemble the waxing and waning in my flow-rate waveforms. ResMed flags the events in your chart as UA events, whereas ResMed flags mine as CA events, which I thought were sort of synonymous with CSA.

So I believe you think my chart shows, not CSR, but periodic breathing.

Is ASV treatment more appropriate for this type of periodic breathing than my APAP? Is continued APAP treatment likely to result in an improvement in the periodic breathing?

[Sleeprider]

Part of the problem with the chart I posted is that the leak rate is very high so not all events are properly identified. The CSR flag is generally shown for a pattern that Resmed has modeled as representative of CSR, but you should not consider it to be diagnostic. You can do a search of threads on the forum using the string, Is this CSR site:apneaboard.com or Do I have CSR site:apneaboard.com, and you should come up with a lot of examples of members that share your concern. You will also see a lot of variation in the patterns and interpretations of the charts. We can only really say that you have indicated no conditions or diagnostics that would result in CSR, and the periodic breathing and central apnea of treatment onset mixed apnea can often resemble CSR. CSR tends to be extremely persistent and consistent compared to idiopathic central apnea and periodic breathing, and normally associated with serious health problems that the patient is usually aware of.

On a more personal note, my dad died of heart failure and ultimately CSR and respiratory failure, before ASV was a common therapy. As a result I became interested on learning about these conditions and trying to help those that could be helped. At the same time, it has become obvious that many healthy individuals exhibit symptoms that may mimic CSR, and of course central or mixed apnea for a wide variety of reasons. I think it's important that people like you not worry excessively about a problem that is easily mitigated or treated once you have eliminated the possibility of heart failure and left ventricular insufficiency through simple health screening and /or electrocardiogram.

[Gideon]

I use a much simpler explanation. Read and understand SlepRiders explanation for a bit of a deep dive.
Our drive to breathe is mainly driven by the need to remove CO2 and it's byproducts from our system. The need for oxygen does not provide this drive to breathe, among other things the need for oxygen may result in faster breathing. So with the need to flush CO2 flush from our system we breathe. Note here that any PAP machine increases this flushing and so does increased pressure and pressure support or EPR. If the CO2 levels go below your apneic threshold a central apnea occurs. You stop breathing and CO2 levels increase and once your levels are above your apneic threshold you resume breathing. With a bit of lag you keep increasing and over breathing resulting in flushing out too much CO2 resulting in the waxing and waning pattern typical of this breathing.

As I said this is the simple explanation. SlepRiders explanation delves into a much more technical review of how this all works.

[DevinJones]

Sleeprider, I understand what you said about the CSR flags in ResMed and will search the threads for similar breathing patterns in other members.

I also understand what you said about differentiating true CSR from other related breathing patterns that exist in people without serious medical conditions such as CHF, etc.


That's great that you're doing everything you can to help people prevent and treat some of the medical conditions that affected your father.

My late parents also suffered from serious medical conditions, including heart failure, respiratory failure, atrial fibrillation, Parkinson's, strokes, and more. So I want to be proactive now and do what I can to prevent serious medical conditions in me.


That's good advice not to worry about the diagnostic label of a condition that I should be able to effectively treat with the right PAP device. Yes, my cardiac and other medical screening tests have ruled out heart failure and the other conditions you referred to earlier.

On Monday, I'm going to contact the DME about trying to get a new ResMed ASV device if you think that it would be an appropriate choice for the kind of central events that showed up when I tried APAP for a week. It seems to be the ideal treatment if I can get the insurance coverage.

Thanks.

[DevinJones]

Gideon, I understand your explanation regarding the drive to breathe and CO2 levels. With your explanation and Sleeprider's detailed explanation, the topic is becoming quite clear now. Thank you.