complex sleep apnea and BiPaP use.

What SAG is politely telling us is that we plebs are walking where angels fear to tread when it comes to meddling with these machines without serious clinical support from a respiratory specialist (respiratory physician).

We at times come across as the historical image of a line of people walking through the landscape, each with one of their hands on the person in front & all walking in the blind knowledge that someone we believe knows where they are going, is leading us somewhere we would like to be

But thanks to the glimpses we get from people like SAG, some of us may eventually get there

DSM

(& some of us may not - perhaps a flip of a coin is the most accurate way to figure out our own likelihood of a succesful journey )

Assuming I read dsm's last comments correctly, I'd like to second his thanks for SAG's participation here. I'd be very surprised if SAG were not an experienced sleep disorder specialist. I find his comments extraordinarily useful, civil, and witty, all welcome additions to this forum.

kinnerstreet wrote:I know when I have a bad apnea (I assume it is centralized) because I wake up feeling dizzy and like my body is in a panic ... vibration feeling from head to toe etc. I know this sounds weird .. but it's true.

Brian, I'm surprised nobody else pointed out to you that the feeling you are describing is identical to that which results from hyperventilation. (Physicians often misdiagnose this as panic attacks as well.) During hyperventilation, you simply exhale too much of the carbon dioxide in your blood stream.

However, hyperventilation could be caused by the machine forcing you to breathe too rapidly, or it could result from overcompensation subsequent to an apnea.

My point here is simply to make you aware that if moving the machine timing in one direction doesn't solve your problem, then don't be reluctant to move it back the other way.

Regards,
Bill (who, unfortunately, has experience with hyperventilation)

cwsanfor wrote:I'd be very surprised if SAG were not an experienced sleep disorder specialist.

Indeed! SAG's comments for the entire time I've participated in this forum have displayed such insights. I was glad to note that he finally decided to register recently.

Regards,
Bill

cwsanfor wrote:Assuming I read dsm's last comments correctly, I'd like to second his thanks for SAG's participation here. <snip>.

You did


My comments really are as much self parody as anything so I hope no one feels they are any target for this brand of humour.

What keeps coming back to me is how we here stray across the line that divides medical advice versus common user experience advice.

I fear some of us (myself included) have at times strayed over the line into the realm of offering public medical advice in areas we are simply novices in. The old saying a little knowledge can be dangerous comes to mind.

What SAG does for us (IMHO) is remind us of just what a specialised field the areas of respiratory complications are when outside the realm of straight cpap needs.

I am glad he does this in such an uncluttered and easily understood fashion because it can be such a complicated topic.

I am going to try to keep to the areas of discussion of how cpap works or might work & how we can improve our own lot & try to help others in their use of what has been prescribed to them.


DSM

NightHawkeye wrote:

kinnerstreet wrote:I know when I have a bad apnea (I assume it is centralized) because I wake up feeling dizzy and like my body is in a panic ... vibration feeling from head to toe etc. I know this sounds weird .. but it's true.

Brian, I'm surprised nobody else pointed out to you that the feeling you are describing is identical to that which results from hyperventilation. (Physicians often misdiagnose this as panic attacks as well.) During hyperventilation, you simply exhale too much of the carbon dioxide in your blood stream.

However, hyperventilation could be caused by the machine forcing you to breathe too rapidly, or it could result from overcompensation subsequent to an apnea.

My point here is simply to make you aware that if moving the machine timing in one direction doesn't solve your problem, then don't be reluctant to move it back the other way.

Regards,
Bill (who, unfortunately, has experience with hyperventilation)

Bill,

Very astute (IMHO) - I saw that possibility but credit to you for honing in on it.

Cheers

DSM

Thought this simple summary of 'Hypocapnia' might be helpful. (I realaise there are other threads on the topic but just wanted to add this simple definition).

DSM

http://en.wikipedia.org/wiki/Hypocapnia

Sorry for the confusion. I meant that I wasn't made aware of having centralized apnea until after my second session where they used a machine. As such, I am not sure if I had a significant number/amount of centralized episodes until after I was tested with a breathing machine (first test is done without a Cpap/Bipap machine ... the second is with a Cpap/Bipap).

Regarding CO2: They had trouble keeping my O2 levels above 85 during the test/study, and so that is probably why they upped the rate of breaths.

I appreciate the info on comfort vs effectiveness. My goal is to breath as normal as possible during sleep without waking up having the feeling that I need to tear this strange object (which I am convinced is one of those aliens that jumped out of an egg like structure and has wrapped itself around my head with the intent on smothering me while trying to implant some creature into my abdomen which will later burst out of my chest cavity while I am stuffing my face in front of a bunch of people at work) off my face ....

I need to have my oxygen levels up because they were running pretty low during the test/study. B4 using the machine I'd have major nightmares and panic dreams, and wake up feeling like I was vibrating inside with this horrible feeling of dread .... oh, and a feeling like there just wasn't enough air on this planet to quench the desire in my lungs. The first night on the machine, I had dreams and those dreams were wonderful. I woke up refreshed for the first time in many years.

I do note, however, that I wake up about every hour or two when I use the machine. I wake feeling like I am trying to take a breath and I can't because something is covering my mouth (claustrophobia feeling). If I wait a second or two, I can take some breaths but not enough to fill my lungs and I feel a kind of panic .. thus it wakes me. I take the mask off ... rub my face ... and go back to sleep. This still gives me a better sleep than without the machine .. but if I can find a way to sleep the night through AND not jeapordize the centralized apnea 'cure' ... I would like to do that. I guess I'm just wondering if setting my Insp/IPAP to 1.5 instead of what the lab had it set at (which was 1 sec) am I at risk of losing the optimal prevention of Centralized apnea.

Again, I appreciate all comments. I am in 'learning mode' here. I realize how annoying a noob can be. I've been on the net for over 16 years (started when you had to use a mainframe to log onto an irc server in order to chat because there was no such thing as a Web client that displayed GUI (graphic user interface) and well, not many could config X windows over Unix. I have run many groups over different types of servers .. etc. The point; I empathize with you all for the tolerance you exercise in addressing someone like me who is new. I suppose we've all been new at some time or another ... and boy, don'cha just hate freshmen sometimes?

Hey, thanx again to everyone... I mean that sincerely.

StillAnotherGuest wrote:Perhaps a better starting point would be to ask what the heck it is you're trying to fix. In your opening comment, you said

kinnerstreet wrote:It is funny though, I don't know if I showed signs of centralized during my first study (without a machine)... I'll have to check on that.

And getting all the way up to BiPAP in S/T Mode if you didn't have any central or mixed apneas on diagnostic opens up a whole new discussion. You might want to investigate that before you wing them dials around too much.

Rise time is discussed in this thread:

Rise Time in the Synchrony S/T

Where it is noted:

While changing rise time on BiPAP machines may give you a feeling of additional comfort while you are awake, the effect it has on breathing while you're sleeping may be something you don't necessarily want. Keeping in mind that the BiPAP S/T is designed primarily to address respiratory failure, sleep apnea as a hobby, and two kinds (at least) of sleep apnea at that, not all adjustments are interchangeable.

To illustrate this, here's a range of rise time settings (1, 3, and 6) for a Respironics Synchrony BiPAP S/T. The Inspiratory Time is set at 3.0 seconds (a little long, but it'll show the effect a little more clearly) and it is allowed to trigger in the Timed Mode.



The effect of rise time is to gradually increase the pressure over period of time. Feels comfortable, yes, but reduces the time spent at peak (effective therapeutic) pressure. If you're using this to overcome the effect of hypopneas, this may not be an issue.

If you're using it to address central apneas, however, a change in rise time could significantly change the effect of trying to generate a reasonable facsimile of a normal breath. Using BiPAP in this case is trying to create a volume breath, and the volume delivered is based on the flow rate times the duration of flow. By prolonging rise time, flow rate is reduced for a significant portion of the breath, resulting in a lower tidal volume (the infamous "area under the curve" concept).

Using BiPAP to overcome central apnea is frequently not completely effective. Adding a lengthy rise time may further compromise the ability of the machine to treat CSA.

BiPAP can be used to address obstructive events, in which case it is used chiefly as a comfort measure (especially if the baseline CPAP requirement is over about 13 cmH2O).

BiPAP S/T can be used to address central events (also respiratory failure, but let's skip that for now). In this case, one of the chief goals is to control pCO2 (usually to try to get it a little bit higher, as contradictory as that sounds). Long inspiratory times, high rates, and rapid rise times are all contrary to that goal.

If that's what your goal is.
SAG

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, bipap, CPAP, CSA

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CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, bipap, CPAP, CSA

kinnerstreet wrote:Regarding CO2: They had trouble keeping my O2 levels above 85 during the test/study, and so that is probably why they upped the rate of breaths.

I wouldn't doubt it, Brian, but simply upping the breathing rate can replace the slow death apnea/hypoxia problem with quick death from hypocapnia. (As stated in DSM's link, hypocapnia can quickly be fatal.) As others have recently posted about, supplemental oxygen may be the right therapy in this circumstance rather than increasing breath rate.

I'd recommend you not ignore the hypocapnia symptoms you are experiencing, Brian. Your physician needs to be made aware of these as soon as possible. (Also, you need to make sure that your physician understands what hypocapnia is and its implications, otherwise get another physician.)

It sounds like xPAP therapy has helped you a lot already, Brian, but it also sounds like further adjustments are in order.

Regards,
Bill

StillAnotherGuest wrote:Perhaps a better starting point would be to ask what the heck it is you're trying to fix. In your opening comment, you said

kinnerstreet wrote:It is funny though, I don't know if I showed signs of centralized during my first study (without a machine)... I'll have to check on that.

And getting all the way up to BiPAP in S/T Mode if you didn't have any central or mixed apneas on diagnostic opens up a whole new discussion. You might want to investigate that before you wing them dials around too much.

Brian, it might be helpful if you ask the sleep lab where you had your study, or your doctor, for a copy of the reports from your sleep study. Both nights if it was a two night study. At any rate, ask for more than just a one page summary report. Ask for the complete report, which should be at least several pages, up to about a dozen pages. A complete report that includes the sleep architecture chart, the titration chart...lotsa' charts/graphs. For both PSG studies - baseline and titration.

When you get those, post 'em here and on the sleep studies forum of apneasupport.org Perhaps sleepydave over there or StillAnotherGuest here will take a look at your study data and be able to give you a better idea about "what the heck it is you're trying to fix." That really is an absolutely essential first step to understanding what's going on with your sleep disordered breathing during sleep. Might also provide more insight into what machine/what settings are likely to work well for you if the sleep professionals you are going to don't have the time or are not responsive to your questions.

This question is directed to SAG.

In seeking to understand 'Mixed Apnea', how does the following simplified definition sound ...

1) An Apnea that starts out as a Central but becomes an Obstructive Apnea due to the airway blocking while the Central was in progress and characterized by the extra breathing effort required to resume breathing

2) A pattern of Obstructive Apneas that become Central Apneas due to excessive CPAP pressure being applied by a CPAP device.

I realise this goes a little beyond the earlier discussion & examples but am wondering how accurate this description is.

Tks

DSM

Mixed apnea:

If both central and obstructive apnea occur during the same episode, this is termed Mixed Apnea.

Snoredog,

In most publications, that is how it is characterised (as you stated it). But SAG raised a very interesting point - that Mixed Apnea (in the context we started discussing it), only existed as a Central that became Obstructive & he produced charts to illustrate this.

I was trying to figure out where pressure induced Centrals fit in the picture as there seems to be conflicting opinion around the industry about what that kind of Apnea is classified as. OSA occurs, Auto raises pressure, if it is raised to high it can induce Centrals. What is the accurate classification. Some say Mixed Apnea. I was interested in SAG's definition (plus the hope he will produce another very helpful chart
)

Cheers

DSM

The mechanism for mixed apneas was described 20 years ago in

A possible mechanism for mixed apnea in obstructive sleep apnea
C Iber, SF Davies, RC Chapman and MM Mahowald Chest, Vol 89, pp. 800-805

Hypopneas or pauses in respiratory effort frequently precede episodes of obstructive sleep apnea resulting in mixed apneas. We studied five subjects after chronic tracheostomy for obstructive sleep apnea. During stable non-REM (NREM) sleep, subjects breathed entirely through the tracheostomy. Tracheostomy occlusion caused experimental obstructive apnea which lasted 13.9 +/- 4.7 sec and ended with transient arousal and pharyngeal opening. At the end of the apnea there was marked hyperventilation (inspired minute ventilation rose 21.6 +/- 3.5 L on the first breath) followed by hypocapnia, hypopnea, and pauses in inspiratory effort as the subjects resumed NREM sleep. Hypocapnia was greater before inspiratory pauses lasting at least 5 sec than before shorter pauses (PETco2, 4.2 +/- 1.8 mm Hg below baseline vs 1.2 +/- 2.5 mm Hg below baseline). In three patients, pauses in inspiratory effort following experimental obstructive apnea were prevented by administration of 4 percent CO2 and 40 percent O2 inspired gas. This study suggests that: hyperventilation with hypocapnia occurs at the termination of obstructive apneas, and hypocapnia may be responsible for the attenuation or cessation of respiratory effort initiating the subsequent cycle of obstruction.

This comes back to the issue of disruption of controller gain as the cause of the central component. The obstructive component of mixed apneas should be corrected by positive pressure, so you should at least give CPAP a shot if you've got a bunch of mixed apneas. Course, the central component could also get worse.

Interestingly, these guys used enriched CO2 to address that. Hmmm, that sounds vaguely familiar...
SAG

dsm wrote:SAG raised a very interesting point - that Mixed Apnea (in the context we started discussing it), only existed as a Central that became Obstructive & he produced charts to illustrate this.

Although the two mixed apneas on the chart might appear that way, my understanding of what SAG said was this:

StillAnotherGuest wrote:It's probably better conceptually (and realistically) to consider that a mixed apnea starts out as both obstructive and central. The airway is probably closed, but this is not fully realized until effort brings it to the forefront.
SAG

To me, that's a little different from "only existed as a Central that became Obstructive".

But perhaps I'm quibbling. SAG did say "probably closed" (underscore mine).

Seriously, this stuff is difficult to understand.