Does ASV Benefit Long-Term?

[VisitorX]

I am trying to understand if there is any solid evidence that ASV improves either survival or long-term morbidity in users who have complex / mixed apnea but do not have heart failure. Can anyone point me to clear-cut studies of such benefits?

I'll give a bit more background (some of it copied form another post on a somewhat different topic) that will help clarify why I'm asking.

The SERV-HF study was done on patients with diagnosed heart failure, and as I understand it a sub-group analysis of patients in that study suggested that not only the intent-to-treat group but also the actual group of ASV users had worse outcomes that the control group (which I believe, but don't recall for sure, used standard CPAP, or perhaps nothing). I know that these findings are still being evaluated and that there are questions about whether the problems (assuming they even are real) arose not from ASV per se but from the relatively aggressive algorithm used by Resmed as opposed to Respironics. But assuming this is a real problem and is due to ASV per se, the assumption seems to be that patients with complex / mixed sleep apnea who do not have heart failure will not experience serious long-term harms. 

This assumption seems to gain some indirect support from the fact that the SERV-HR study showed (as I understand it) that outcomes among heart failure patients were worse in those patients with the worst heart failure (lowest ejection fraction). So extrapolating this finding in reverse, one could argue that among patients with increasingly good heart function above a certain healthy threshold there would be no danger. But this is a bit of a creative extrapolation, so I wouldn't want to place too much weight on it, even if I could validate the data better through a more careful reading of the literature. So I don't mean to automatically suggest that the study should raise concerns for those without heart failure.

At the same time, I did notice that the ASV patients with heart failure (even as they had worse outcomes over time) had what we would normally think of as improvements in their situations: better oxygenation, much lower AHIs and AIs, and even less daytime sleepiness (which is not surprising given the improved AHIs and likely fewer arousals that one would expect as a result). (At the same time, I don't believe they had actual improvements in "Qualify of Life," notwithstanding the reduced sleepiness.) So that gave me pause, since I know that such symptomatic benefits are an important reason why non-heart failure patients use ASV; and these symptomatic benefits may impart a sense of confidence such as, "I'm feeling better so I can assume I'm also benefitting long term."

Though there may be other concerns as well, the main one I'm currently focusing on with ASV has to do with a reversal of normal pressure changes in the chest during the respiratory cycle. During normal inspiration (without ASV), the pressure tends to decrease, and this leads to better venous return to the heart, greater cardiac filling during diastole, and then leads to (I believe) increased cardiac output. But during ASV, the pressure increases during inspiration, which would lead to decreased cardiac filling and decreased cardiac outputs during inspiration. Conversely, during normal  (no ASV) expiration, pressure increases, whereas with ASV it decreases. This may not automatically be bad, but it is a fairly impressive reversal from normal, and in this respect at least ASV is quite non-physiological.

Ultimately these comments about physiology may be irrelevant, but they do point me in the direction of wanting to see persuasive outcome studies showing no increase in either survival or major morbidity. Have such studies been done? Can anyone point me to any / comment on any of them?

Further, I have read that among heart failure patients, those with prominent Cheyne-Stokes respiration (in addition to those with worse ejection fraction) tended to do less well. Have any studies been done looking at non-heart failure patients with prominent CSR to see what their outcomes are?

Thanks!

[SarcasticDave94]

Absolutely there’s long term benefits for me using my ASV. I don’t mean this sarcastically, but because of my ASV, I can breathe properly while sleeping. Non-treated, I had severe apnea. CPAP and BPAP brought out severe central apnea. Sleeping included incredibly loud snoring, morning headaches, chronic fatigue. One of my sleep studies (I believe BPAP) included statistics of 124 central apnea to 24 obstructive.

As was required, I did an echocardiogram to obtain the ASV. It reported my LVEF was at 55%. I also have a family history with high blood pressure, heart attacks, congestive heart failure. Of those, I’ve had only high blood pressure. Add COPD onto my mixed apnea.

Do I have other research data on LVEF, ASV, CHF, and/or CSR? I’ve reviewed some of these items but I didn’t think to take notes. If I had done so, I’d share it.

[foxfire]

I was just going through the abstracts from this past the Sleep 2019 conference this past June.

See abstract 0549 on page A219: DOES ADAPTIVE SERVO VENTILATION HELP RESOLVE CENTRAL SLEEP APNEA?

https://academic.oup.com/DocumentLibrary..._42_S1.pdf

Short answer is that yes, it does. (However the study sample size was very small).

[sheepless]

being an asv user, I'm very interested in the topic. I haven't done a lot of reading on it but the only time and place I've seen this come up was once recently on this forum. most of what I 'know' is subjective and that's that I feel better with asv than I did on apap. if my long term outcome is the same with asv as with no treatment, I'll still take asv for that reason alone. obviously I hope for a better outcome as well. I look forward to reading more about what you learn about this topic, VisitorX.

[VisitorX]

Thanks, I'll keep exploring, and keep seeking data from those here who are more knowledgable than I. The two positive reports just given confirm my impression about subjective benefits -- and they may well bear directly on improved survival. But again, symptomatic relief (lower AHI, lower centrals, better oxygenation, less daytime sleepiness) occurred in the treatment group with heart failure in the SERV-HF study (though they did not improve in overall subjective measures of quality of life (QOL), which I assume many here have.) But it comes down to long-term survival. If that improves, or even remains the same in the context of better QOL, great. But what if it tuns out there is a tradeoff between this QOL and survival? Then we're dealing with some more difficult choices. Again, I'm not saying this trade off is real. It may not be. And even if it is, one might still opt for the QOL. But I'd like to know based on objective data, to the extent possible.

[Matt00926]

The SERVE-HF study was very poorly done -- I would ignore it completely.

https://journal.chestnet.org/article/S00...5/fulltext

Just one of many goodie excerpts:

"Fourth, we note that adherence to ASV therapy was generally quite low, with an average usage of 3.7 hours/night overall and about 40% of patients accumulating ≤ 3 hours per night (Table S3 in the Supplementary Appendix)."

If you pre-screen and take only ill patients, they only use a device - which was improperly titrated to boot - and they use it for less than half of the time they sleep, so no wonder they found there was no mortality benefit, and/or that the patient continued to decline.

[tmoody]

I sometimes feel that i slept better on plain old CPAP than on ASV, but since my old CPAP machine wasn't data I can't say what was really going on. Some nights, I feel like the ASV is waking me up, whereas I never felt like that with CPAP, but who knows how many centrals I was having?

I think I've seen some studies that suggest that at least some people with mixed apnea do better with constant pressure, but I'm really not sure. I know biPap without ASV usually makes centrals worse. If our could put my machine into CPAP more I'd experiment, but I don't think that can be done.

[SarcasticDave94]

I sometimes feel that i slept better on plain old CPAP than on ASV, but since my old CPAP machine wasn't data I can't say what was really going on. Some nights, I feel like the ASV is waking me up, whereas I never felt like that with CPAP, but who knows how many centrals I was having?

I think I've seen some studies that suggest that at least some people with mixed apnea do better with constant pressure, but I'm really not sure. I know biPap without ASV usually makes centrals worse. If our could put my machine into CPAP more I'd experiment, but I don't think that can be done.

I'm not sure if your unit can switch modes. I know my ResMed 10 series AirCurve ASV can go CPAP mode if I so choose.

[tmoody]

I sometimes feel that i slept better on plain old CPAP than on ASV, but since my old CPAP machine wasn't data I can't say what was really going on. Some nights, I feel like the ASV is waking me up, whereas I never felt like that with CPAP, but who knows how many centrals I was having?

I think I've seen some studies that suggest that at least some people with mixed apnea do better with constant pressure, but I'm really not sure. I know biPap without ASV usually makes centrals worse. If our could put my machine into CPAP more I'd experiment, but I don't think that can be done.

I'm not sure if your unit can switch modes. I know my ResMed 10 series AirCurve ASV can go CPAP mode if I so choose.

Nope, can't do it with the PRS1.

I know that when I was switched from plain CPAP at 11 cmH20 to auto-BiPAP (Dreamstation), I started seeing large amounts of PB, centrals, and AHI that was seldom under 10. A subsequent split study confirmed complex apnea and I was switched to the PRS1 ASV. I have switched doctors since then. My original doc was a pulmonologist, but he got sick and left the practice. His replacement, also a pulmonologist, was reluctant to answer questions. This is how I ended up at this forum (and others), in fact. I needed answers that I wasn't getting.

I switched to a neuro sleep doctor because I felt that the pulmonologists were simply more comfortable with OSA as a mechanical problem, but had little to say about CSA. That said, my neuro sleep doctor doesn't have time for many questions either. And I have raised the very question that the OP raises: Is ASV actually beneficial in the long run? The OP's observation that "During normal inspiration (without ASV), the pressure tends to decrease, and this leads to better venous return to the heart, greater cardiac filling during diastole, and then leads to (I believe) increased cardiac output. But during ASV, the pressure increases during inspiration, which would lead to decreased cardiac filling and decreased cardiac outputs during inspiration. Conversely, during normal  (no ASV) expiration, pressure increases, whereas with ASV it decreases. This may not automatically be bad, but it is a fairly impressive reversal from normal, and in this respect at least ASV is quite non-physiological" is astute. My non-expert impression is that ASV feels less natural than straight CPAP.

On a "good" night, for me, the ASV aspect of the machine isn't doing much. There are few timed breaths; almost all are patient-triggered. On a "bad" night, there are more timed breaths and fewer patient-triggered breaths. Looking over old Sleepyhead charts, these "bad" periods tend to fall into two clusters, one at 1:00 am or so, the other at 4:30 or 5:00, not too long before I wake up. The rest of the night tends to be fairly quiet. During those clusters, the ASV algorithm is working hard to power me through. At 5:00 am, my sleep is light enough that it may wake me up. Occasionally that'll happen at 1:00. So the question is: If the algorithm for correcting centrals/hypos is sometimes interfering with my sleep, is the cure any better than the problem?

If I could do straight CPAP mode, I'd be able to see how many centrals I get and how long they last and make a determination.

[sheepless]

for me, breathing with the resmed asv feels far easier and more natural than with the resmed apap. after the first night or two I no longer noticed the asv pressure support nudging me to breathe when I failed to initiate an inhale. everything is in sync. not so with apap. I've gone back to apap a couple times since asv and each time my ahi is higher (say, under ~5 vs <1) and it's more work to try to keep up with the machine, meaning more arousals.

"Is ASV actually beneficial in the long run?"

compared to what? comparing asv to 'normal inspiration' doesn't seem like a useful comparison for us since it doesn't account for the fact that apneacs don't breathe normally, a fact that leads to plenty of its own significant negative consequences. my guess is more negatives than using asv, in fact. a better comparison might be asv vs apap (assuming apap breathing is also different from 'normal' breathing).

"...is the cure any better than the problem?"

arousal from sensitivity to pressure is undesirable, sure, but I'd say it's worth it if it's also keeping us breathing and oxygenated.