Auto SV, Encore and SpO2 questions

[BiPAPBefuddled]

Hi to all,

And thanks in advance for your help.

After a year, I'm still struggling. Dr. and RT of little help with the following questions ... in fact, not very helpful at all.

1. What is the functional / theraputic difference between EPAP < IPAP minimum and EPAP = IPAP minimum on Respironics BiPAP Auto SV? Does an EPAP = IPAP setting automatically disable this machine with respect to treatment of central or mixed apnea?

2. The higher the IPAP Maximum setting, the faster the blower runs(same machine). Does the higher "pressure support in waiting" allow the machine to function more efficiently or is it just wasting electricity. if one's maximum IPAP demand never exceeds, say, 14 cm H2O, is it necessary to have the IPAP max set at 21 cm for an EPAP setting of 11 cm ? (Per the recommended differential of 10 cm H2O rule)

3. Re: the EncoreViewer data, specifically on the Daily Details page: It seems that when just one apnea event is flagged on the Sleep Therapy line, it wrongly adds a full value of one to the AHI instead of doing the "per hour math."

4. And are the EncoreViewer flags indications of events that were successfully treated by the machine or of events that occurred in addition to those treated by the machine?

5. I have had good SpO2 readings, but sometimes dozens of pulse events according to my recording pulse oximeter. (MS50SE) Resting HR mid-50's, not an athlete. Of what significance is a pulse event anyway?

New to the forum and so thankful you are willing to help,

Paul

[HoseCrusher]

I don't know about your machine settings, but a pulse event is usually a drop in heart rate of 6 beats per minute lasting for a period of 8 seconds. This can precede a desaturation event, or simply be the result of settling down after a change in position. Variations in heat rate can also trigger pulse events.

There is a loose correlation between pulse events and arousal's, but there are usually more pulse events than arousal's. This indicates that not every pulse event results in an arousal.

If you have ever worn a heart monitor that automatically records events, it triggers on a change in heart rate in the 15 - 30 beats per minute range over a period of 30 - 60 seconds. This is from a cardiologist who is using pulse data in part to evaluate heart function, if I understood him correctly.

When I hand over my pulse oximetery data to my cardiologist, I set the parameters to score a pulse event with a change in 15 beats per minute lasting for a period of 30 seconds, and he is pleased with that information. Of course, without the corresponding ECG data, the pulse data is only seen as "interesting..." He is actually more interested in the O2 saturation data. I was given quite a lecture on all the bad things that happen to your heart when your O2 drops below 90%.

[JohnBFisher]

... After a year, I'm still struggling. Dr. and RT of little help with the following questions ... in fact, not very helpful at all. ...

Unfortunately, ASV units are fairly new devices and seldom employed. As a result the doctors and respiratory therapists often know very little about them at a detailed level. But don't worry. Their knowledge will grow.

... 1. What is the functional / therapeutic difference between EPAP < IPAP minimum and EPAP = IPAP minimum on Respironics BiPAP Auto SV? Does an EPAP = IPAP setting automatically disable this machine with respect to treatment of central or mixed apnea? ...

EPAP < IPAP is BiLevel mode. EPAP = IPAP is CPAP mode. That is if the Exhalation pressure is less than the Inhalation pressure it means the unit is providing two different pressures during normal breathing. Thus, it operates as a BiLevel Positive Airway Pressure (BiPAP) device. If the pressures are equal, then it provides Continuous Positive Airway Pressure (CPAP) therapy.

... 2. The higher the IPAP Maximum setting, the faster the blower runs(same machine). Does the higher "pressure support in waiting" allow the machine to function more efficiently or is it just wasting electricity. if one's maximum IPAP demand never exceeds, say, 14 cm H2O, is it necessary to have the IPAP max set at 21 cm for an EPAP setting of 11 cm ? (Per the recommended differential of 10 cm H2O rule) ...

Normally BiLevel devices are set with a 4cm H2O spread between the EPAP value and the IPAP value. It might be spread a little further, but not all that much. If the pressure difference is more than that, you might want to talk with your doctor and/or the sleep lab about that.

*IF* you have a Respironics BiPAP AutoSV unit (and not the advanced unit), then the device has two different IPAP values. IPAPmin and IPAPmax. The difference between EPAP and IPAPmin normally would be about 4cm H20. This is the BiLevel pressure. The IPAPmax sets the upper level when it detects a flow rate that will not match the previous three minutes. It then bumps the pressure upto the higher IPAP value (IPAPmax). This helps sustain your breathing during either a central apnea or the low point of periodic breathing.

During this higher pressure state, the motor will increase, the power demands will also increase. But it's perfectly normal. It is not wasting electricity. It is adjusting itself to meet your breathing needs. This is the Adaptive Servo-Ventilation (ASV) mode in operation.

By the way, you can read more about your unit at:

http://www.healthcare.philips.com/main/ ... efault.wpd

Here is the Setup Guide for your unit:

http://global.respironics.com/UserGuide ... 043629.pdf

And here is the Users Guide for your unit:

http://global.respironics.com/UserGuide ... 040200.pdf

... 3. Re: the EncoreViewer data, specifically on the Daily Details page: It seems that when just one apnea event is flagged on the Sleep Therapy line, it wrongly adds a full value of one to the AHI instead of doing the "per hour math." ...

Let me see if I understand this correctly. Let's say you sleep 10 hours. You have one apnea. It says you have an AHI score of 1? There are two components of the AHI score. Your Apnea index. In this case it would be 10 hours / 1 apnea ... or ... 0.1 AI. However, the AHI score also includes hypopneas (decrease or restricted breathing). If that is close to 1 events per hour, then you would have 10 hours / 10 hypopneas (for the entire time) ... or ... 1.0 AHI. In the case of an AHI of 1.0 with an AI of 0.1, we know your hypopnea index is 0.9.

By the way, that is an EXCELLENT number.

... 4. And are the EncoreViewer flags indications of events that were successfully treated by the machine or of events that occurred in addition to those treated by the machine? ...

It flags events that the machine could not address. It is VERY proactive in addressing breathing problems. On an ASV unit, it is VERY rare to have an AHI over 5.

... 5. I have had good SpO2 readings, but sometimes dozens of pulse events according to my recording pulse oximeter. (MS50SE) Resting HR mid-50's, not an athlete. Of what significance is a pulse event anyway? ...

See the previous note on that.

... New to the forum and so thankful you are willing to help, ...

Paul, welcome to CPAPtalk.com. Please register. When you register, you can list your equipment. This will help us better answer your specific questions. We can address issues with the machine, mask and humidifier that YOU have, not just using general terms. Here's a pointer on how to register your equipment in your user profile:

wiki/index.php/Registering_Equipment_in_User_Profile

[OutaSync]

3. Re: the EncoreViewer data, specifically on the Daily Details page: It seems that when just one apnea event is flagged on the Sleep Therapy line, it wrongly adds a full value of one to the AHI instead of doing the "per hour math."

You are right about the way Encore scores AHI on a SV. If I have only one apnea OR hypopnea during the night, it will score my AHI as 1.0. On the daily reports it never gives an AHI below 1 if you have had either an apnea or a hypopnea. It can't do simple math, but it will keep me breathing all night.

Bev

[BiPAPBefuddled]

Thanks for your responses.

PAP decreasingly effective and causing some side-effects. Trying to tweak things a bit. Too fatigued to think/write clearly sometimes. I'll get my profile up very soon.

Paul

[Bons]

I'm glad for your questions because I'm learning things I didn't know. I have one of those DME's that don't seem to know much, so I have an appointment in early Nov. with the head of the sleep clinic at one of the teaching hospitals in Philly. Figure if he doesn't know anything about the machine, no one in the area will. I actually emailed Phillips Respironics and they coached me through a tweak to solve one of my problems with the machine.

[Bons]

Hey John,
What is the advantage or disadvantage of the PR bipap autoSV vs the "advanced" version?

[Bons]

I've heard a lot about Auto SV, I heard it was better than cpap but no one says why it is better. Why is it better?

Amy,
There's a difference between Auto SV, and an auto setting on the cpap. An auto setting on your cpap lets you set a range for your pressure, so that you only get the amount of pressure that you need at a given time - lower when you are doing fine, rising to deal with an apnea occurance. An SV ( adaptive servo-ventilation) is a different kind of machine altogether and is designed for people who have problems with central or complex apneas - it learns your regular breathing rhythm and then tries to help you maintain it. It has a setting for a minimum number of breaths per minute, for example, and definitely lets you know when it thinks you need to take a breath with a quick blast of higher pressure.
Others can tell you a lot more about both machines.

[JohnBFisher]

... What is the advantage or disadvantage of the PR bipap autoSV vs the "advanced" version? ...

Questions, questions ... Let's tackle this one first.

The biggest difference between the earlier version and the "advanced" version is that the advanced version provides auto-titration of the BiLevel pressures. That is, it uses a range of pressures from a low to high for the exhalation pressure. It then adds a pressure support value to get the inhalation pressure. So, let's say your exhalation pressure need ranges from 8 to 12. Then on top of that a prescription may call for an inhalation pressure of 4 above that value. That is the pressure support. So, your inhalation pressure would range from 12 to 16, depending on the number of apneas and hypopneas observed.

And of course on top of that the Auto Servo-Ventilation support kicks in as needed to address either periodic breathing or central apneas.

In addition the Advanced model improves on the measurements it takes. This improvement can help you better manage your condition. Of course, bring the information to your doctor and discuss any changes with your doctor. I am pretty adamant about involving your medical team before making changes on an ASV unit. This is especially true for someone with heart issues.

Hope that helps.

[JohnBFisher]

... I've heard a lot about Auto SV, I heard it was better than cpap but no one says why it is better. Why is it better? ...

Greetings AmyHarper! I've not had the chance to yet welcome you to the forum! Hope you find answers and help here to make your journey toward better sleep more effective and easier.

For those of us who need an ASV unit, it is usually a Godsend. But better? Not unless you need it.

If you don't mind, I'll back up a bit and provide an overview of some of the different xPAP (various Positive Airway Pressure) devices.

We all know about CPAP. That provides a Continuous Positive Airway Pressure. As the name implies it provides just one pressure that is continuous. Most people (80% to 90%) can take CPAP without any problem.

But in fact CPAP has one big downfall. It only provides one pressure. When we are on our backs we generally need more pressure than on our sides. When we are in REM sleep we generally need more pressure than in other stages of sleep. To address this need, researchers developed CPAP machines that adjust their pressure based on the needs of the patient. This Automatic CPAP units are generally called APAP units.

But some people have difficulty exhaling against a single pressure. Almost 18 years ago I had a sleep study where the sleep tech found that my sleep was disturbed while breathing against a constant pressure. So, he tried shifting me to a BiLevel Positive Airway Pressure (BiPAP) support. That did the trick. You could see in the graphs that the number of interruptions of my sleep fell off dramatically when I slept with BiPAP. So, a BiLevel PAP (BiPAP) unit provides a lower exhalation pressure than the inhalation pressure. This helps a smaller number of people than CPAP. Due to the difference in pressure and the need to sense the breathing of the user, these machines cost more. So, they are prescribed only as needed.

As with CPAP, researchers found that BiPAP did not address all needs, so they developed an automatic mode of BiPAP. Usually just called BiPAP Auto. In that case, the exhalation pressure is defined as a range of pressures (let's say from 8 to 12cm H2O) and the inhalation pressure is defined by a pressure support value. Let's say the sleep tech finds that you breathe best with a pressure support of 4cm H2O, then your inhalation pressure would range from 12 to 16cm H2O. This inhalation pressure is based on the CURRENT exhalation pressure. So, if you current exhalation pressure is 9.5, the inhalation pressure is 13.5 (9.5 plus 4).

There are some people (due to various reasons, including problems with the heart, problems with the lungs, problems with the central nervous system, problems with drugs) who find they just have problems regulating breathing during their sleep. Some people have central sleep apnea. There is NO effort to breathe at all. This is not due to an obstruction. It is just a failure to breathe. Some people develop what is know as periodic breathing. Most commonly this results from heart problems, though it can occur due to other issues such as living at a high altitude. Some people develop central apneas in the presence of increased pressure. So, CPAP or BiPAP induce the central apneas. This is Complex Sleep Apnea.

In all of those instances, there is a common underlying problem that occurs. For various reasons the body fails to regulate the breathing. Essentially, the body fails to breathe normally. The breathing is either very shallow or ceases. This is the 'undershoot' part of the cycle. In that case, the CO2 levels increase until the body senses the need to breathe. The body then races to compensate. The breathing rate increases. The body then blows off the CO2 in the blood. However, for these users, their bodies tend to blow off too much CO2. This results in the overshoot portion of the cycle. This waxing and waning (overshoot/undershoot) of breathing can not be solved through a normal CPAP or BiPAP. Researchers found that when the undershoot cycle occurs, the cycle can be broken if breathing is supported during that part of the cycle. So, they developed Adaptive Servo-Ventilation (ASV) units. These units almost like a ventilator during the undershoot part of the cycle. Because it helps maintain the O2 levels and helps the body expel CO2, it helps regulate breathing.

Resmed was the first company to research and develop an ASV unit. It is their Resmed VPAP AdaptSV unit. Respironics developed their BiPAP Auto SV unit. They essentially provide the same support. There are differences, but they both provide the adaptive servo-ventilation during that low point in this cycle.

As you might imagine, the complexity of these units is quite astounding. They need to track the breathing rate over the past few minutes, determine if the current breathing rate will fall short of the normal need and adjust the pressure to provide the adaptive servo-ventilation in case it does not meet the average need. This means that these units have many, many more settings that can be adjusted. Worse yet, improper adjustment of those settings can cause serious harm, especially for patients with heart issues.

So, are they better? Not really. They just provide a different type of breath support for those users who need it. In fact, if all I needed was a CPAP unit, I would be much happier with that. It's MUCH cheaper. Much smaller. And better understood by everyone.

Hope that helps answer your question.

[Bons]

Thanks, teacher John. I wouldn't dream of changing my ASV without consulting a doctor, except for lowering my minimum breaths per minute. He had that set at ten, and I was only doing 6-7 when awake,so the machine and I were pretty much at war. I moved it down to six figuring it couldn't hurt me too much. Since I was put on the machine without being titrated for it, and my current sleep doctor refuses to discuss any of the settings with me, I am going to a teaching hospital next week for a consult with the head of their sleep clinic.

[JohnBFisher]

... I wouldn't dream of changing my ASV without consulting a doctor, except for lowering my minimum breaths per minute. He had that set at ten, and I was only doing 6-7 when awake, so the machine and I were pretty much at war. ...

Yikes! That's quite a difference. The lower rate will be certain you don't slow too much. If I am not mistaken, the AutoSV Advanced and an "Auto" mode for the breaths per minute. That might be a better option in the long run.

... Since I was put on the machine without being titrated for it ...

Ugh! This is EXACTLY why I think it is valid that we look to the experiences of others to help us guide our own therapy. We each must be our own advocate. But we need to know what we need to know to be able to be effective. Sounds illogical, and it feels like that. To make the system work, we need to know which questions to ask to help guide the process. But until we learn what those questions are ...

This is just my opinion, but you should NEVER be put on an AVS or AVAPS system without proper titration. At the best, it would mean you are at war with the machine. At worst, if you had cardio-pulmonary problems, it could make things worse.

... and my current sleep doctor refuses to discuss any of the settings with me ...

Some doctors are overwhelmed by patients who ask questions they can not answer. If that happens, it's generally an indication you need to see a specialist. If your doctor does not request you see a specialist, this is when you need to be your own advocate and request a specialist.

... I am going to a teaching hospital next week for a consult with the head of their sleep clinic. ...

As you are doing! Hope that consult goes well.

[BiPAPBefuddled]

Hi again,

And thanks so much for your responses.

Still have a few questions:

First, I really want to register. In fact, I already did. Well, sort of ... A few weeks ago, I completed the form – email address, “yes, I am a human” etc. – everything except a username. Couldn’t think of anything clever, so I started to type in “NeedSleep.” Unfortunately, the dog nudged my right elbow after the “d” which caused me to accidentally hit the “enter” key which means my username is “Need.” It’s pretty lame - and needlessly meaningless.

I have tried to undo it, but to no avail. Seems one can change anything in one’s profile except the username. I also tried to register a new username. No luck with that either because “[my] email address is already associated with another username.” Any ideas? Is there an administrator or moderator who can wave a wand o’er the database?

Second, does anybody know how to set the time on the Respironics BiPAP Auto SV / SmartCard / EncoreViewer? While the date is correct, the time displayed on my data is approximately 35 minutes slow. That is, if I start the machine at, say, 10:49 pm, the time will show up on the next morning’s screen/printout as 10:14 pm. Same thing for shutdown in the morning – it’s also off by the same 35 minutes. It’s not a big deal, but it would make correlation with the SpO2 and “ZEO” sleep data a little easier.

Third, after being on the Auto SV for a few months, it began to turn on me – at least that’s how it feels. Just as a couple of others have reported on this forum, the machine often seems to take on a mind of its own. The machine’s breath rate and pressure escalate without cause. I try to sync my breathing with it, but it won’t give in. If I turn the machine off and right back on, the rate returns to “normal” for a few breaths. But then the same scenario recurs. The feeling is frightening. Can’t breathe, in or out. When I’m halfway through an inhale, it seems to stop the flow … almost sucking the air out. Same thing when I exhale … except that it seems to try to pop or push the air back in. To say that it wakes me up is an understatement. And it also can happen before I’ve fallen asleep.

I suspect that this behavior is rooted in the machine’s “three minute programming” - that it somehow over-reacts or ends up in an over-compensation endless loop. I’ll try to provide more details after I get registered. Meanwhile, any thoughts?

Thanks,

Paul

[Baby's Daddy]

Please excuse one more dumb question from a "newbie" but I'm not sure I totally understood everything stated above.
If the LCD indicates 8 Hours sleep and the AHI indicates 6.0, does that mean AHI of 0.75 or 6.0 per hour?
Thank you again for all the valuable information from very nice people.

[Bons]

Paul,
Can you check and change your minimum breaths per minute that the machine is programmed for? Reducing mine helped reduce the number of fights that I have before falling asleep. I think the other issue is "rise time" but I don't know how to change that.
I'm counting the days til I see my new sleep doctor and getting some answers and advice. Have you asked your RT or someone from the DME about dealing with the forced breathing? Any advice I can get through you will be appreciated!
Screaming into the face mask in frustration can sure make the hose bounce!!