Cardiac oscillations Question

chrisp · Post by **chrisp** » Tue Dec 14, 2004 6:59 pm

What does it mean in the equipment literature : Detects apneas with and without cardiac oscillations .. How does it detect cardiac symptoms ..Wouldn't you need to be wired for that ..Refering to the 420E ..

Ted the Titrator can you answer this ?

cheers,

Chrisp

Nev · Post by **Nev** » Wed Dec 15, 2004 12:43 am

The significance of detecting "cardiac oscillations" is that the airway is still open and your heart beats are causing small fluctuations in the flow of air in and out of your lungs. This means you are having a central apnea rather than an apnea caused by flow limitation i.e. closed airway. If your airway is closed the fluctuations from heartbeats can't get back to the machine. The 420E will not increase pressure for an apnea (or hypopnea) with cardiac oscillations beyond a preset limit as going too high (above about 10 cmH2O) can induce more centrals (as your brain thinks there's plenty of air coming in to your lungs so why need to breathe??). It will however keep increasing pressure for an apnea without cardiac oscillations because the apnea is due to closed airway.

The Resmed auto spirit cuts off at 10 cm for any kind of apnea so it's your bad luck if you are having a fair dinkum apnea rather than a central. It will however keep increasing pressure above 10 for a hypopnea whether it is central or not.

WillSucceed · Post by **WillSucceed** » Wed Dec 15, 2004 6:51 am

Interesting line of discussion.

Do you have any knowledge about whether or not software upgrades for the Spirit (I assume that the Spirit can be upgraded over time) will address this issue? Or, is it that the small sensor tube running through 420E hose makes it more sensitive to detecting apnea's with cardiac oscillation.

I'm debating buying an auto machine and my sleep study did show some central apneas at pressure of 11, 12 & 13.

chrisp · Post by **chrisp** » Wed Dec 15, 2004 11:38 am

Thanks for the answer. So what you are saying is the 420E hears my heartbeat thru the hose. Is that correct ? I'll have more questions after I figure out the explanation.. Bummer about the Spirit as I have 1 also ..Its at Resmed now getting repaired. Is there a software upgrade ? I think that was the problem with it . It won't turn on the humidifier...

Thank You,

Chris

Nev · Post by **Nev** » Thu Dec 16, 2004 1:28 am

Not so much "hears" as senses the small change in air pressure at the mask caused by the heartbeat against the lungs. If you hit yourself in the chest with your fist it makes you breathe out harder - the heartbeat is the same sort of thing only gentler!

Puritan Bennett would claim that the small sensor tube picks this effect up better, but there's no reason in principle why you shouldn't be able to detect it at the machine end of the main hose if your sensor was sensitive enough. That's where Resmed detect pressure anyway.

I don't know whether a software update (within the machine) would do it - it may well need additional or modified hardware as well - but ResMed may build in a similar feature to a future machine.

chrisp · Post by **chrisp** » Tue Dec 21, 2004 4:48 pm

Topping for Fifi. Central apnea question..

Chris

Fifi · Post by **Fifi** » Thu Dec 23, 2004 5:10 pm

I see it Chrisp. But I cant help wondering:
Is there any medical evidence to support Puritan Bennetts claim. A good selling angle, I'm sure, as it gives their machines a different but possible important rescourse that the other machines at this moment in time do not posess.

Is it just talk on the part of B.P. Could it all be Bull? Well meant I 'm sure, they may just like/wish their machines have this additional function. Does it actually work, or is it merely at the theoretical stage? With no one able to prove or disprove it.

Is there any factual medical evidence that could possibly substanciate their claim, from an independent source, would be even better.

Not that I have a distrusting streak in me or anything.

Titrator · Post by **Titrator** » Thu Dec 23, 2004 6:41 pm

Hi Folks,

Nev is right on the money. The 420e is a very sofisticated autopap.

You can set the threshold of when it will stop reacting to apnea as well. All the others stop at 10cm. I had mine set to 14cm on the "Command on Apnea" setting.

Nev, you from Tennessee?

Ted

SWS · Post by **SWS** » Thu Dec 23, 2004 9:45 pm

The AutoSet Spirit uses a paddle actuated hall effect sensor rather than a more sensitive pneumotach. Because The Spirit A10 algorithm elected to limit apnea response to 10 cm (as part of a best statistical fit across the apneic population), there really was no reason to deploy a more sensitive pneumotach sensor. A firmware upgrade will not enable the Spirit's paddle-actuated hall effect sensor to ever detect a resident heart-pulse pressure wave. I don't think ResMed has incentive to, either, as that A10 algorithm is a great statistical fit for so many apneic patients.

The RemStar uses a pneumotach sensor as well, it will respond to apneas with up to two pressure increments before backing off for fear of inducing runaway (pressure induced) central apneas. What I have not yet heard specifically about the RemStar Auto is that it will limit its command on apnea to only 10 cm. That is a surprise to me, as their non-responsive apnea approach combined with a sensitive pneumotach should not impose a technical "command-on-apnea" limitation of only 10 cm. It is very specifically ResMed that elects to do this with their statistically savvy A10 approach.

While the 420e attempts to sense cardiac oscillations as an indication of central apneas, it only does so with a specificity rating somewhere in the low eight-some-percent range. That's the best home-PAP technology can do without a respiration "effort" belt as the PSG employs. But at a specificity rating in the low eighty-some-percent range, I am not surprised that other manufacturers have elected to NOT use this as central apnea detection criteria.

In summary here are the three manufacturers' approaches to central apneas:

1) PB=cardiac oscillation detection
2) Resmed=A10 statistical approach with a 10 cm limit
3) Respironics=2 non-responsive pressure increment attempts

-SWS · Post by **-SWS** » Thu Dec 23, 2004 10:14 pm

Sorry for this typo in my above post: "While the 420e attempts to sense cardiac oscillations as an indication of central apneas, it only does so with a specificity rating somewhere in the low eight-some-percent range."

That's an eighty-some-percent specificity range---NOT eight-some-percent!

Wow! That typo alone is enough to cause cardiac osscillations! Sorry...

chrisp · Post by **chrisp** » Thu Dec 23, 2004 10:29 pm

Thanks SWS,
One more question. Which unit would be best for a patient with central apneas and hypopneas with no obstructive apneas and no mixed apneas ? I'm am wanting to purchase another . I have a Spirit (broken at resmed) and a 420E. What is the best choice for my situation ?

Cheers,

Chris

Nev · Post by **Nev** » Thu Dec 23, 2004 10:33 pm

Hi Titrator

Sorry to disappoint you - I'm in Queensland, Australia not Tennessee!

Have you got Frys over there? I've heard your burgers come with fries in USA - ours used to come with chips but McDonalds have changed that!!

Best wiwhes

Nev

-SWS · Post by **-SWS** » Thu Dec 23, 2004 11:13 pm

Well, Chris, Titrator is a very good expert to listen to regarding this topic. The Spirit is a superb machine in general (perhaps even the best all-around machine for the apneic population as a whole---who knows). However, the 420e is a better machine in my opinion for a patient that is known to have mixed and central apneas that are not significant. In my opinion any patient having significant central apneas should steer clear of any AutoPAP and go for a BiLevel machine that is specifically designed to address central apneas.

Again, Titrator is really the seasoned veteran regarding this particular topic. He be the man from TN!

-SWS · Post by **-SWS** » Thu Dec 23, 2004 11:15 pm

Sorry, Titrator! I know you're not from TN---it's KY!

I think we're even since you once confused me for a teacher.

Titrator · Post by **Titrator** » Thu Dec 23, 2004 11:44 pm

Hi SWS,

I grew up in Oak Ridge, Tennessee. Dad was a scientist. I live in KY now.. only about 200 miles from my hometown. Several years ago when I worked as a technical trainer, I was transfered to Louisville, and met a gal from Frankfort, so here I am.

Nev, I know a guy named Nevin, and he is a bright guy, I thought you might be him.

SWS, thanks for the compliments, but you seem to express your technical knowledge much better than me. Not bad for a teacher.

What amazes me iis the brotherhood that we all share. The communication is great, and the people are sincere.

One thing i have learned from the year of sleep studies that I was allowed to do, is that cpap, bipap, autopap are all good ways to treat sleep apnea.
i try and stay open minded about all the equiptment, because they all end up at the same result. a sound nights sleep and better health.

Ted...

Cardiac oscillations Question