Cardiogenic Oscillations

[Geer1]

I know I have seen theories/comments about users believing the small oscillations you sometimes see on flow rate chart mimic heart rate.

That is true and they are called cardiogenic oscillations. I just stumbled upon the proper terminology researching some other things. Just figured some might want to know as there appears to be some articles and studies on the subject that may be of interest like this one (https://www.semanticscholar.org/paper/Cardiogenic-oscillations-on-the-airflow-signal-as-a-Ayappa-Norman/e8012fdbbe537b5a87fffa429b1752767c655bcf)

I only briefly skimmed over the article but what I believe it is saying is something I had already been surmising and that being when you see longer extended breaths with these cardiogenic oscillations they are similar to a central apnea. Apnea would be the wrong term due to duration required but rather the brain slowing respiration rate and pausing between breaths. 

Anyways figured a few might find this interesting.

[Dormeo]

Thanks -- interesting article! I believe another term in use is "cardioballistic" oscillation or artifact. My own charts exhibit this. As a result of my cardiogenic oscillations, when I was using a ResMed Airsense 10 Autoset, the machine would give me distorted data about the length of my inhalation and exhalation. By contrast, the ResMed Aircurve Vauto counts correctly. No idea why the two machines from the same company report these data differently.

I don't have many obstructive events, so my sample is limited, but I think my observations match those in the study: the oscillation can be observed during the CAs but not during the OAs. The machine's frequent, anxious probings fuzz up the image, but it is clear to me that my heartbeat can be seen during the CAs, while during the OAs there is just a flat caterpillar-type line.

[Geer1]

As they discussed they believe it is due to muscle relaxation during central apnea/periods which makes sense to me since if the body is relaxed after a breath out then the expansion/contraction of the heart will have more affect on the lungs than when muscles are working. You can easily see/test this by laying down, exhaling then relaxing and you will likely be able to see your heartbeat in your chest/belly movements but if you flex or actively breath you can't really see it (at least for me).

[Dormeo]

Just for the heck of it, I experimented before going to sleep, first just exhaling and waiting, then a few breaths later, exhaling and tensing my chest muscles.  You can see the difference: oscillations during the first pause and none during the second.  In the other breaths in this image, you can see the oscillations that occur during all my normal pauses between breaths.