Questionable advice from Pulmomologist

Guest · Post by **Guest** » Sat Mar 19, 2005 2:59 pm

Thanks Ted,

My hypoventilation is due from the weight too. And I'm on added oxygen (the oxygen rose to normal levels within a week of starting the oxygen).

You explanations make me feel better about my doctor's choice of machine. Always good to hear it from more than one source. Thanks.
You're great at describing things.

wading thru the muck! · Post by **wading thru the muck!** » Sat Mar 19, 2005 3:16 pm

Thanks Ted,

I understand and agree with every post you make on the CPAP/BiPAP subject. I get very frustrated with understanding the points of view of many of the posts in between yours.

My issue, without regard to the science of BiPAP function, is that Docs are switching people titrated with CPAP to using BiPAP machines as an alternative approach in an effort to improve comfort and thus compliance. If this switch results in exposing them to higher pressures rather than just lowering the EPAP pressure then I think this is a faulty strategy.

As a forum of (mostly) xPAP users who aren't medical profesionals, Our expertise is in the areas of comfort and compliance and not the intricasies of air splint modification of obstuctive airway geometry.

This is certainly interesting conversation, but again my concern is in the area of preventing mistreatment that results in non-compliance. This question was the focus of the post originating this and other threads on the subject

Titrator · Post by **Titrator** » Sat Mar 19, 2005 3:23 pm

Hi Wader,

I am with you on the compliance/comfort side of the fence. I am not only work for the hairclub for men, I am a client. LOL.. I think you guys get the picture.

Ted

rested gal · Post by **rested gal** » Sat Mar 19, 2005 4:48 pm

I agree with Wader that when doctors prescribe bipap for people who have difficulty breathing out against pressure but who DON'T have an overriding health reason (as described by Titrator) to be put specifically on a bi-level machine, the doctors are skipping a step that could possibly give them two ways for relief from pressure in the long run....an Autopap WITH C-Flex.

I'm not a doctor, but I'd venture a guess that most patients who can't tolerate straight cpap because of exhalation pressure would do fine on an Auto with C-flex. Seems to me that autopap with C-Flex would be the best "next step" for most (again, unless there were a definite underlying health problem) rather than subjecting the patient to a steady high pressure from a bipap, even though the patient was getting relief on exhalation.

It's very possible that the amount of relief on exhalation that C-Flex would give them might be enough relief - for most. At the same time, they might also spend most of their sleep at the lower pressures in general that an autopap can deliver as needed, to proactively keep the airway open.

I'm with you in that regard, Wader, when talking about people in general who have no very special need to be on bi-level machines. Besides some doctors' distrust of autopaps in general, I doubt that many of them are even aware there's now an autopap that can give relief on exhalation at the same time. Right now, only one autopap is available which can be set to operate that way - the Respironics REMstar Auto with C-Flex.

FL andy · Post by **FL andy** » Sat Mar 19, 2005 5:17 pm

[quote="Titrator"]
Bilevel machines use software just like auto machines. The data is comprehensive, you get tidal volume and minute ventilation, respiratory rate. These are parameters you do not get with 99% of all autopaps.
Ted

Andy follows:
I don't have tidal volume and minute ventilation or respiratory rate on my Respironics BibPap Pro 2 using the latest Encore software.

Ted, what manufacturer did you see this on?

Andy

FL andy · Post by **FL andy** » Sat Mar 19, 2005 5:39 pm

rested gal wrote:I agree with Wader that when doctors prescribe bipap for people who have difficulty breathing out against pressure but who DON'T have an overriding health reason (as described by Titrator) to be put specifically on a bi-level machine, the doctors are skipping a step that could possibly give them two ways for relief from pressure in the long run....an Autopap WITH C-Flex.
.

rested gol,

Are you saying that C-Flex on an AutoPap can/does lower the expiration pressure to the same degree that a BiPap machine with BiFlex does? If so, could you please point me to some documentation. If not, I do not understand what you are saying.

Can a C-Flex reduce expiratory pressure four or more points?

I mean this post in the most polite and respectful manner possible. You have far, far more experience AND expertise than I do. I simply haven't read that in any authoritative source (yet). If you are correct I truly would like to read about it.

Andy

rested gal · Post by **rested gal** » Sat Mar 19, 2005 6:03 pm

I understand your question, Andy...I'd be asking it too, if I were you. No, C-Flex cannot give the type of precise "set this number for exhalation pressure" that a bi-level machine can give. I'm sorry if I gave that impression.

No one really knows what degree of expiratory relief C-Flex can give, but I seriously doubt it would ever give as wide a range between inhale/exhale that bi-level machines can be set for. C-Flex can't be set for an exact "this many cm's". Even Respironics doesn't try to say how many cm's each of the three C-Flex settings represents....apparently the degree of relief C-Flex gives on each exhalation varies from patient to patient, and from exhalation to exhalation within the same patient.

That's why I said, for people who have a specific health reason, like the reasons Titrator mentioned, a bi-level (bipap) would be better. But for the general OSA patient who simply wants the comfort that "less pressure on exhalation" can give, I really think doctors should have them try an autopap (but only if it has C-Flex) first.

Hypoventilation and being on supplemental oxygen would quite likely fall into the category for needing bi-level exhalation relief rather than C-flex's more "vague" (can't think of a better word at the moment ) exhalation relief, but there's no way to know that for an individual patient unless both types of machines were tried.

-SWS · Post by **-SWS** » Sat Mar 19, 2005 7:42 pm

As a forum of (mostly) xPAP users who aren't medical profesionals, Our expertise is in the areas of comfort and compliance and not the intricasies of air splint modification of obstuctive airway geometry.

This is certainly interesting conversation, but again my concern is in the area of preventing mistreatment that results in non-compliance. This question was the focus of the post originating this and other threads on the subject

I think the entire topic of sleep apnea, xPAP therapy, even titration is fair game for us. Admittedly some threads will wander a bit from their original post. It's kind of like getting cardiac patients together for a group discussion. It would, indeed, be fair game for them to discuss and attempt to understand their surgeries---even though surgical technique is not close to being within the realm of their exterpise.

And poor Ted! When he comes out to answer questions he gets beseiged! You have answered my question in a nut shell, Ted. Thanks!

Guest · Post by **Guest** » Sat Mar 19, 2005 8:05 pm

Rested Gal wrote:For a long time I had thought that it took more pressure to deal with apneas than with hypopneas. But when you really think about the simplest definitions:

apnea = full closure of the throat
hypopnea = partial closure of the throat

...then one can see where it wouldn't take as much pressure to open the throat a little bit. Voila' - it's no longer an apnea! The throat is partially open now, so it now meets the definition of an hypopnea. But to get the throat FULLY open so that it no longer can be considered a hypopnea or a limited air flow - it takes even more pressure to push those tissues back completely out of the way.

Great explanation, Rested Gal. Thanks! Indeed, a partially corrected apnea is but a hypopnea. Think of any single full-blown apnea simply as "sleep event A". Now think of yet a different sleep event that is a hypopnea in that same part of the airway. That second sleep event is but a partial closure, yet physiologically identical to "sleep event A" in every other respect. So think of that second obstructive event as "sleep event B". Indeed it will take more pressure to fully correct "sleep event A" than it will to correct "sleep event B".

Yet, if you change names or labels at some midpoint through correction then "sleep event A" is labeled an apnea at onset, yet is labeled a hypopnea at: a) some midpoint in correction, or b) if left in a partially corrected state.

-SWS · Post by **-SWS** » Sat Mar 19, 2005 8:06 pm

"guested" above!

rested gal · Post by **rested gal** » Sat Mar 19, 2005 8:51 pm

SWS, you wrote:

Yet, if you change names or labels at some midpoint through correction

Well, I've been known to switch horses in midstream before...lol!!

Got hypopneas? Ummmm, those are really apneaettes.
Got apneas? Nah, those are really appopneas.

Good thing I'm not the one coming up with definitions or criteria or titrations or prescriptions. I'd be sending everyone home from sleep clinics with a spiffy little autopap/C-Flex, a heated humidifier and a heated hose.

No, that's not a buttonless mouse - it's a "card reader".
No, the CD doesn't have music on it, even if it does say "Encore".

That second booklet? It tells you what allllllll the buttons do.

Here are four masks for ya. Wear whichever you wish, but keep all of them, anyway.

If you have any trouble, call a real doctor and hope for the best!

Titrator · Post by **Titrator** » Sun Mar 20, 2005 10:23 pm

An obstructive apnea is a total cessation of breath for at least 10 seconds, with continued respiratory drive. (The diaphram still moving but no air comming in due to obstruction)

A central apnea is a complete cessation of breath for at least 10 seconds, without respiratory drive. (The diaphram is not moving. No attempt to breathe is being made by the body)

A hypopnea is at least a 30% reduction in airflow with a 3% desaturation.

-SWS · Post by **-SWS** » Sun Mar 20, 2005 10:37 pm

A hypopnea is at least a 30% reduction in airflow with a 3% desaturation.

When you think about it, there are quite a few ways the human airway might achieve a 30% reduction in airflow. The scoring of a hypopnea does not really get into the underlying physiological failure. A soft palat partially closing can cause a hypopnea. So can crowded tonsils, other cranio facial crowding characteristics, etc. cause hypopneas. CPAP inflates the airway to correct obstructions, and an underinflated airway can turn a fully closed obstruction into a partially closed one---or a hypopnea. A constricted airway "high" also yields the same end scoring result as a constricted airway "low"----regardless of obstruction point.

Resmed and PB both recognize some hypopneas to be obstructive in nature while other hypopneas to be central in nature. I'm not sure how or even if the two hypopnea types (central versus obstructive) are distinguished in a PSG. My hunch is that hypopneas are sleep discordered breasthing's great underdifferentiated sleep event.

ozij · Post by **ozij** » Mon Mar 21, 2005 1:56 am

In my PSG I had a band around my diagphragm, which reported diaphragmatic effort, or lack of it. It seems to me central are very easily identified under these conditions.
This measurement is something we don't have when we sleep at home, which is why, imho, xPAP machines cannot distinguish obstructive from central apneas. They have rules of thumb to keep them from blowing air into an otherwise open airway, not because they have identified a central, but because, not having diaphragm info, the can't tell. The rule of thumb is most probably based on a combination of the probability that the airway is actually open, and the risk of blowing into a open airway. It could be (I have no idea if it is or not) that the prbablity of the first is low, but the danger of the second high - in which case you'ld have a lot of false positives - i.e. the machine behaving as though the apnea was central because that is the safest thing to do and not necessarily because that is the most probable interpretation of the data.

-SWS · Post by **-SWS** » Mon Mar 21, 2005 7:11 am

In my PSG I had a band around my diagphragm, which reported diaphragmatic effort, or lack of it.

Yes, I agree full-blown central apneas versus obstructive apneas should be easy to differentiate using this method . But how about partial respiratory effort resulting in what would score as a hypopnea? That would be respiratory-based versus obstruction-based with some intermediate muscular effort registering on the respiratory effort belt. I have seen plenty of patients report in that they have obtructive apneas, central apneas, mixed apneas, and hypopneas. I don't recall any patients ever reporting respiratory-drive based hypopneas, though. I would think that "gray zone" of partial muscular respiratory effort is a very difficult thing to score----but I could be wrong.

PB and Resmed both mention in their published literatire that hypopneas can be central in nature. Yet we just don't hear patients reporting this hypopneic distinction after their garden variety PSG studies. I would even venture to guess that some patients with obesity-related hypoventillation get hypopneas scored with no differentiation (by some/most sleep centers?). I'm sure contrasting hypopnea etiologies are studied and researched, but to what degree are they routinely diagnosed in the field?