Sleep 7.6 Cardiopulmonary Coupling in Sleep: Strengths, Limitations & Future

We break down CPC’s barriers, methodological concerns, and why it could still reshape the future of sleep medicine.

Video Breakdown:

00:11 Challenges & Barriers

01:17 Lack of Clinical Validation

02:46 Advantages of CPC

04:33 Methodological Limitations 05:40 Future Outlook

For the last five minutes, I just wanna quickly go into the strengths and limitations of cardiopulmonary coupling. I think I was surprised that, when you go to the sleep conferences, you know, the big ones like SLEEP or even SRS, CPC is relatively unknown. Not too many people know about it.
There's probably a number of reasons for this lack of popularity. First, it's conceptually hard to understand. It's technically complex. It's difficult to understand the physiology behind it. In fact, there were no papers that explained the low frequency coupling physiological basis.
I had to sort of extract, and I'm not even sure if my explanation is correct or not, but that's my interpretation of low frequency coupling. So it's confusing to begin with. And remember, the band, ranges is different from the low frequency, cardiopulmonary coupling with the HRV.
And so there's gonna be confusion with the low frequency component with an HRV and the low frequency component in the cardiopulmonary coupling. And also, you know, physicians and technologists need retraining to interpret the CPC metrics. So that's some of the barriers there. The other thing is that surprisingly, CPC lacks significant clinical validation.
I was not able to find any RCT even, much less large RCTs, proving that CPC prospectively improves patient outcomes. So, you know, there should be some randomization of having a group of patients getting treatment according to a CPC method and those without, and that randomization has not happened that I could find.
Most of the studies are sort of small cohort studies or single center retrospective investigations. It's also unclear how CPC should be used to manage the patients. I think that will change as we get more and more data. The other issue is the infrastructure and integration challenges. You know, CPC does not fit easily into the existing sleep lab workflow.
And the other challenge is that it's not necessarily reimbursed, although I heard there's a new Medicare rule in place which allows for higher level billing when CPC is added to existing home studies, and apparently this adds like 40 to $60. I have to confirm that, but if that's true, then I think you will see more CPCs being added to home sleep studies.
And then there's obviously a competition for other technologies which distract or remove that tension away from CPC. But there are some key advantages of using cardiopulmonary coupling, and this is why I wanted to make this a topic as part of our sleep webinar series. And the first thing is that it truly quantifies autonomic function.
It directly measures ANS activity and assesses sleep quality and stability beyond traditional staging. And I would have to intuitively say that this may actually do better in terms of clinical outcomes because of the involvement autonomic nervous system compared to the traditional staging system, which is largely based on the EEG, or what's happening in the brain.
But time will tell whether that will actually be true or not. The other thing, it's simple and accessible. You only require a single-lead EKG, or a ring. It makes it far less invasive. Ideal for use in home and wearable devices. And importantly, it allows for multi-night monitoring. So you can longitudinally track the sleep variability and objective responses to therapy over time.
And because it only uses a single-lead EKG or ring, it really avoids all the complex things like putting leads on the head and, all the, wires that's needed for a home PSG. So this really opens up the opportunity to monitor longitudinally sleep quality in many different conditions.
And this CPC algorithm is automatable, and this is objective, it's reproducible, it provides intuitive sleep spectrogram and eliminates the score of subjectivity that we know is seen in the traditional sleep staging system. And we could ideally enhance patient phenotyping because it assesses not only sleep quality, but also AHI and sleep disorder breathing.
But with that being said, there are still some methodological limitations with the CPC itself. I have mentioned that it is unreliable with patients with significant arrhythmias or paced rhythms, and I mentioned that this old system relies on the Fourier analysis, which has certain assumptions.
That the respiration derivation itself is not always perfect. So the EKG derived respiration is good, not great. It can be affected by body position, noise, and may be even more challenging with PPG. These are susceptible to movement artifacts. I mean, that's true for sleep studies as well, but you know, you have, poor EKG or PPGs
and it could be a challenging for individuals with RMS or periodic leg movements. And again, there is some ambiguity physiologically in this interpretation, and I guess this is particularly true with the very low frequency coupling, which, is supposedly, indicates REM versus wakefulness.
And you would need ancillary data such as actigraphy to distinguish the two. But either way, I do think that CPC is gonna be increasingly popular, and this is why I wanted to make this a topic of conversation for you.

Course episodes

Sleep 7.1 Understanding Cardiopulmonary Coupling in Sleep Studies

Sleep 7.2 Cardiopulmonary Coupling: Sleep Staging Classifications

Sleep 7.3 High vs. Low Frequency Coupling in Cardiopulmonary Physiology

Sleep 7.4 Cardiopulmonary Coupling and Sleep Apnea Detection

Sleep 7.5 Traditional vs. Modern CPC Methodology

Sleep 7.6 Cardiopulmonary Coupling in Sleep: Strengths, Limitations & Future