Clear Airway Apnea = Central Apnea?

[rested gal]

And wouldn't it be cheaper to have effort belts (with a wireless link that runs on an AAA battery) included with every auto than to keep trying to deduce effort from a single channel for trending?

I dunno if supplying effort belts along with machines would be cheaper. But it would be more definitive.

I say that the day my sleep center doesn't need belts to differentiate centrals is the day I'll believe my home machine knows the difference without belts, and not a day before.

LOL!!! I'm with ya, there. Well, not "with you" literally at your sleep center...

Seems to me more is known about how bellies and chests move in the general population than how airways move, and the belly and chest are a lot easier to get to. If manufacturers really want to differentiate, it wouldn't be that hard.

Awww, Jeff -- you just want an excuse to show off your ripped abs to the cute l'il sleep tech the CPAP companies would have to send out a couple of times a night to check and see if the belt had loosened or slipped!!

If the manufacturers ever were going to send out an extra strap for anything, I vote they include the leg cut off a pair of pantyhose tights with every mask. (Seriously.)

[jnk]

And wouldn't it be cheaper to have effort belts (with a wireless link that runs on an AAA battery) included with every auto than to keep trying to deduce effort from a single channel for trending?

I dunno if supplying effort belts along with machines would be cheaper. But it would be more definitive.

I say that the day my sleep center doesn't need belts to differentiate centrals is the day I'll believe my home machine knows the difference without belts, and not a day before.

LOL!!! I'm with ya, there. Well, not "with you" literally at your sleep center...

Seems to me more is known about how bellies and chests move in the general population than how airways move, and the belly and chest are a lot easier to get to. If manufacturers really want to differentiate, it wouldn't be that hard.

Awww, Jeff -- you just want an excuse to show off your ripped abs to the cute l'il sleep tech the CPAP companies would have to send out a couple of times a night to check and see if the belt had loosened or slipped!!

If the manufacturers ever were going to send out an extra strap for anything, I vote they include the leg cut off a pair of pantyhose tights with every mask. (Seriously.)

I think one belt that would sense movement, regardless of where it slipped to, would be enough, or at least better than soundwaves, other airwaves, or other airway sensors. The fun part would be that we could post what kind of blue tape could be used at what location to hold it in place for the best data. What would make it cheaper would be the lack of need for R&D. The technology already exists and is proven. It would be easier than what Zeo is doing, I think, and might only be needed for patients that really need differentiation, like ASV people.

Thanks for fielding my newbie-wandering-mind questions, RG. I hope my wanderings in my wonderings are sufficiently related to the original poster's questions.

jeff

ps-The tech would have to bring an ultrasound if she wanted to find anything remotely ab-like, I'm afraid.

[dsm]

Muffy, -SWS I'm having trouble following this thread - could either of you post a glossary of all those short cuts you're using?
And what is "ballistocardiography" in words that a non-physicist can understand?

Thanks,
O.

Ozij,

I'll have a go at offering a simplified explanation.

Ballistocardiography is the 'science' of measuring the heart's pounding/pulsations from outside the body (that is, by non invasive means). In the posts here they are often using the acronym 'COs' (cardiac oscillations). I know you understand the way the Puritan Bennett machines look for heart pulses in the airflow & that I understand to be one approach to employing ballistocardiography (SWS pls correct this if wrong).

So, in this context, I understand it to be about being able to measure the cardiac oscillations through the open airway. There are issues to do with just how open / closed the airway is and also muscle toning affecting the ability to make clear readings and Muffy also pointed out that the type of sensor used can make a big difference. Restated: I understand Muffy is saying that the variation in quality of the sensors makes a very big difference in what can be interpreted and thus skews results.

When it comes to the part about using FOT to sense COs, I am not really following all that is being said. I know FOT is a technique of sending a pulsed air burst down the airway. I understand that the FOT burst can be analyzed when it bounces back, so as to look for COs ?. If no COs are detected/observed then the airway is deemed closed. If COs can be detected in the FOT return signal then the airway is deemed open. But I think we have been shown some examples where it is not so clear cut.

My understanding of the core of this discussion is in the accuracy in determining if an apnea is central or obstructive & up to now, there may not be agreement that it can be done to an acceptable level of accracy (which is what I understand Muffy is pointing out). Part of the discussion is around what technique the Respironics machine is using to make the CA vs OSA apnea determination. My understanding of that is that it is not using FOT ballistocardiography sensing & Muffy is making the point that the technique it is using lacks accuracy.

DSM

#2 From a little bit of extra research I see that most references to ballistocardiography highlight it as measuring the effects of the heart and blood pulsing on the surrounding body and in relationship to the body frame. I take this to be that the heart stroke and blood flow impacts the body around it and that this secondary impact is what is observed & measured. i.e. a Dr can observe a patients body 'vibration' caused by the heart beating & mass of blood flow. What the Dr is seeing is not the 'actual' heartbeat but the effect of a heartbeat and blood flow on the surrounding body. In most conditions the ballistocardiography signal will be in sync with the heart beat as shown on a heart machine.

[-SWS]

Does the airway have to be 100% closed for an apnea to be considered obstructive?

Kind of OT, but I would like to add to this. The below figure is from another thread. This patient demonstrates small bursts of expiratory flow without inspiratory flow i.e. continues to lose lung volume. I would be interested to hear how common this type of apnea is seen in other labs? Of note, flow was measured using a pneumotach which has increased sensitivity.

Greetings, Split. Unfortunately I don't work in either sleep or health. So I can't help with useful anecdotes or data. I will say that phenomenon of high gastric pressure during OA somehow producing unusual and extra expiratory effort is very interesting. I would be most curious if that extra expiratory effort is a slight reflexive response to the stimuli of aspired gastric fluids.

[-SWS]

Muffy, -SWS I'm having trouble following this thread - could either of you post a glossary of all those short cuts you're using?
And what is "ballistocardiography" in words that a non-physicist can understand?

Thanks,
O.

Oops! This thread is hard to follow because it has meandered among various "overly esoteric" technical topics. Sorry about that. Please email or PM me with a list of which terms you'd like to see, and I'll make up a glossary for an upcoming post in this thread.


And regarding "ballistocardiography"... I suspect biomedical purists would disapprove of the loose vernacular this term has received in our current discussion. In the context of this discussion, we have loosely applied that term meaning "heartbeat signals sitting in the patient flow channel". However, in "PSG vernacular", that same term might also loosely apply to intentionally or unintentionally transduced heartbeat signal residing in any relevant PSG channel:

http://www.sleepreviewmag.com/issues/ar ... -04_07.asp

Rather frequently, a false signal or ballistocardiogram artifact will appear in one or both of the effort channels. This can be identified as small to medium sized oscillations in the thoracic or abdominal movement channels. The cause of the ballistocardiogram is the force of the heart beat causing the chest to expand and contract slightly but at a rate exactly equal to the ongoing heart rate. Noting the almost perfect correlation between the oscillations in the effort channels and the ongoing electrocardiography (ECG) signal allows one to identify such ballistocardiogram artifact. The main point to recognize is that there is little or no movement in either the abdominal or thoracic movement channels for 10 seconds or longer. Again, such an event is considered by some to be clinically significant only if either an arousal of some sort and/or an oxygen desaturation follows it.

[split_city]

Does the airway have to be 100% closed for an apnea to be considered obstructive?

Kind of OT, but I would like to add to this. The below figure is from another thread. This patient demonstrates small bursts of expiratory flow without inspiratory flow i.e. continues to lose lung volume. I would be interested to hear how common this type of apnea is seen in other labs? Of note, flow was measured using a pneumotach which has increased sensitivity.

Greetings, Split. Unfortunately I don't work in either sleep or health. So I can't help with useful anecdotes or data. I will say that phenomenon of high gastric pressure during OA somehow producing unusual and extra expiratory effort is very interesting. I would be most curious if that extra expiratory effort is a slight reflexive response to the stimuli of aspired gastric fluids.

Maybe.

Alternatively, I reckon it's simply due to a "global" increase in respiratory drive. Genioglossus activity frequently increases towards the end of respiratory events in response to chemostimuli i.e. rise in CO2 and mechanstimuli i.e. rise in negative airway pressure (note: more so during hypopneas given the upper airway is still exposed to negative airway pressure. May/may not be true during apneas because the upper airway has collapsed, thus the mechanoreceptors in the airway may not be exposed to negative airway pressure. Really depends on the site of collapse).

The increase in those expiratory gastric pressure swings is likely a consequence of contraction of the abdominal muscles. For example:

[/quote]

You can again see the increase in expiratory gastric pressure swings in line with increase contraction of the abdominal muscles (EMGab trace). With sufficient intraluminal pressure (careful, Muffy might get upset when discussing the effects of increased abdominal contraction on airway pressure ), this could transiently re-open the airway and allow further decrements in lung volume below resting EELV. The precise role of expiratory drive in sleep is not known but may be similar to the orderly pattern of ventilatory muscle recruitment during exercise which likely contributes to a reduced EELV. Expiratory abdominal muscle contraction could place the diaphragm on a more favourable part of its length-tension curve and increase the contractile efficiency during subsequent inspiratory efforts. However, any increase in efficiency is only likely to be beneficial following inspiratory airflow restoration and may not be present if the diaphragm is over-stretched as is likely below resting EELV in obese patients already with an elevated diaphragm. In addition, in the context of upper airway obstruction, such a response likely exacerbates airway collapse, via further diaphragm ascent and reduced airway traction.

Anyway, I digress. But I guess the point comes back to an earlier question: Does the airway have to be 100% closed to be scored as an apnea. Does this mean closed for the entire duration of the apnea? Or only closed during the inspiratory phase of the apnea. The later would be my understanding.

But back to the topic of the thread......

[Muffy]

...careful, Muffy might get upset when discussing the effects of increased abdominal contraction on airway pressure...

Upset? When has Muffy ever gotten upset (other than the BYU thing)?

Muffy

[Muffy]

Okay, Beltran in the 2006 NLCS was right up there, too.

Muffy

[-SWS]

The only time I ever PERSONALLY saw Muffy upset was when Volvo decided to put ballistocardiography inside their vehicles... without asking his or her opinion of upgrading all the seat belts to respiratory effort belts... <Vaudeville drum roll>

Doctor Split, thanks for that alternate explanation... and your research!

[Muffy]

Then there was the 2007 Fiesta Bowl. That was pretty upsetting.

Muffy

[Muffy]

Of course, the tragic incident involving Cousin Claire was also very upsetting...



Muffy

[split_city]

The only time I ever PERSONALLY saw Muffy upset was when Volvo decided to put ballistocardiography inside their vehicles... without asking his or her opinion of upgrading all the seat belts to respiratory effort belts... <Vaudeville drum roll>

Haha, I'm only messing with the Muffster. I have thoroughly enjoyed our discussions.

Doctor Split, thanks for that alternate explanation... and your research!

Don't quite have the Dr in the title just yet . But I'm happy to play along

[Muffy]

Cousin Jebidiah had a similar end, but he didn't seem to mind as much:



Muffy

[-SWS]

Don't quite have the Dr in the title just yet .

Well, we're counting that festive occasion down in nanoseconds here in North America. Celebrate it as you may in Australia, Sir...

But I guess the point comes back to an earlier question: Does the airway have to be 100% closed to be scored as an apnea. Does this mean closed for the entire duration of the apnea? Or only closed during the inspiratory phase of the apnea. The later would be my understanding.

How about those borderline events sitting right around the flow-reduction demarcation for hypopnea/apnea scoring? My layperson's understanding is that some of those borderline obstructive apneas should entail a partially open airway... Obstructive hypopneas just above that flow-reduction demarcation should as well I would think.

The only time I ever PERSONALLY saw Muffy upset was when Volvo decided to put ballistocardiography inside their vehicles... without asking his or her opinion of upgrading all the seat belts to respiratory effort belts... <Vaudeville drum roll>

Did I mention there was automotive mayhem to pay after Volvo stuck to their guns with the ordinary seat belts...?


But looking at the previous page... I must say that Muffy's relatives were victimized by some rather beautiful culinary Sirens!

[ozij]

Thanks for all the serious replies, guys. That "ballisto" in the cardiography really threw me for a bit -- dsm and -SWS you've explained it perfectly.

That doesn't look like a Volvo to me, -SWS, rather more like like Chevy or a Subaru. Maybe Muffy was so upset he lost his aim.... going start reading again ans see where that leads me.

Thanks.

O.