Squishing the belly increases AHI

NotMuffy · Post by **NotMuffy** » Fri Oct 08, 2010 7:31 am

split_city wrote:
NotMuffy wrote:
split_city wrote:Nah, that 1439 is not correct. Mine says 04:09 i.e. about 4am. I don't know why yours is different.
Probably got messed up crossing the International Date Line. The point remains, then, that this guy can put up stable Duece.
Maybe something to consider....

Sleep. 2009 Mar 1;32(3):361-8.
Airway dilator muscle activity and lung volume during stable breathing in obstructive sleep apnea.

Jordan AS, White DP, Lo YL, Wellman A, Eckert DJ, Yim-Yeh S, Eikermann M, Smith SA, Stevenson KE, Malhotra A.

Division of Sleep Medicine, Harvard Medical School, Boston, MA, USA. ajordan@rics.bwh.harvard.edu
Abstract

STUDY OBJECTIVES: Many patients with obstructive sleep apnea (OSA) have spontaneous periods of stable flow limited breathing during sleep without respiratory events or arousals. In addition, OSA is often more severe during REM than NREM and more severe during stage 2 than slow wave sleep (SWS). The physiological mechanisms for these observations are unknown. Thus we aimed to determine whether the activity of two upper airway dilator muscles (genioglossus and tensor palatini) or end-expiratory lung volume (EELV) differ between (1) spontaneously occurring stable and cyclical breathing and (2) different sleep stages in OSA.

DESIGN: Physiologic observation.

SETTING: Sleep physiology laboratory.

STUDY PARTICIPANTS: 15 OSA patients with documented periods of spontaneous stable breathing.

INTERVENTION: Subjects were instrumented with intramuscular electrodes for genioglossus and tensor palatini electromyograms (EMG(GG) and EMG(TP)), chest and abdominal magnetometers (EELV measurement), an epiglottic pressure catheter (respiratory effort), and a mask and pneumotachograph (airflow/ventilation). Patients slept supine overnight without CPAP.

MEASUREMENTS AND RESULTS: Peak and Tonic EMG(GG) were significantly lower during cyclical (85.4 +/- 2.7 and 94.6 +/- 4.7 % total activity) than stable breathing (109.4 +/- 0.4 and 103 +/- 0.8% total activity, respectively). During respiratory events in REM, tonic EMG(GG) activity was lower than during respiratory events in stage 2 (71.9 +/- 5.1 and 119.6 +/- 5.6% total activity). EMG(GG) did not differ between stable stage 2 and stable SWS (98.9 +/- 3.2 versus 109.7 +/- 4.4% total activity), nor did EMG(TP) or EELV differ in any breathing condition/sleep stage.

CONCLUSIONS: Increased genioglossus muscle tone is associated with spontaneous periods of stable flow limited breathing in the OSA subjects studied. Reductions in genioglossus activity during REM may explain the higher severity of OSA in that stage. Increased lung volume and tensor palatini activity do not appear to be major mechanisms enabling spontaneous stable flow limited breathing periods.

He got the idea for that study from this poster:

viewtopic/p526909/viewtopic.php?f=1&t=1 ... em#p108817

Staying in some kind of arousal-free sleep (probably at least Stage 2) for even a few minutes increases the likelihood of getting to a stable NREM sleep state and sustaining it, and the tendency to periodic breathing will lessen dramatically. So anybody with sleep-onset centrals and/or a low arousal threshold is gonna have trouble.

AKA sleep instability begets breathing instability.

CollegeGirl · Post by **CollegeGirl** » Sat Oct 09, 2010 2:58 am

split_city wrote:
CollegeGirl wrote:Forgive my completely unscientific intrusion.

In the vast majority of cases, doesn't supine sleeping at least somewhat eliminate apneas? In a person with quite a lot of abdominal fat, wouldn't this position "squish the belly" quite a bit? If your hypothesis were true, shouldn't it make them worse?

I am a very large (no really... very large) woman with a whole lot of abdominal fat that gets compressed when I sleep on my stomach. Yet, I have far fewer apneas in this position. Obviously one person is anecdotal, but given what we know about supine sleeping meaning fewer apneas for many, I don't see how your hypothesis could be true.
Sorry, a little confused as you discuss both supine and prone (stomach). OSA is generally worse (not better) when you sleep on your back. Sleeping on your stomach would likely have different results. None of my patients slept prone so I am unsure whether the results from my study can extend to those who sleep on their stomach.

Oh, i do recall my supervisor telling me they tried to run a pilot study years ago (before I worked there), where they removed some of the slats in a wooden bed and had OSA patients sleep prone with their stomach sort of dangling through the hole in the bottom of the bed to see if OSA severity decreased. I don't think the study was very successful as patients were just too uncomfortable.

Sorry, you're absolutely right. I said supine when I meant prone.

Let me see if I can simplify my question.

You say abdominal compression leads to more apneas. Sleeping on the stomach leads to greater abdominal compression as your belly is pushed inward by the mattress. But we know sleeping on the stomach leads to FEWER apneas for most. This is what I'm trying to get at.

split_city · Post by **split_city** » Sat Oct 09, 2010 3:17 am

CollegeGirl wrote:
split_city wrote:
CollegeGirl wrote:Forgive my completely unscientific intrusion.

In the vast majority of cases, doesn't supine sleeping at least somewhat eliminate apneas? In a person with quite a lot of abdominal fat, wouldn't this position "squish the belly" quite a bit? If your hypothesis were true, shouldn't it make them worse?

I am a very large (no really... very large) woman with a whole lot of abdominal fat that gets compressed when I sleep on my stomach. Yet, I have far fewer apneas in this position. Obviously one person is anecdotal, but given what we know about supine sleeping meaning fewer apneas for many, I don't see how your hypothesis could be true.
Sorry, a little confused as you discuss both supine and prone (stomach). OSA is generally worse (not better) when you sleep on your back. Sleeping on your stomach would likely have different results. None of my patients slept prone so I am unsure whether the results from my study can extend to those who sleep on their stomach.

Oh, i do recall my supervisor telling me they tried to run a pilot study years ago (before I worked there), where they removed some of the slats in a wooden bed and had OSA patients sleep prone with their stomach sort of dangling through the hole in the bottom of the bed to see if OSA severity decreased. I don't think the study was very successful as patients were just too uncomfortable.
Sorry, you're absolutely right. I said supine when I meant prone.

Let me see if I can simplify my question.

You say abdominal compression leads to more apneas. Sleeping on the stomach leads to greater abdominal compression as your belly is pushed inward by the mattress. But we know sleeping on the stomach leads to FEWER apneas for most. This is what I'm trying to get at.

Yeah good point. I don't know the answer why there are fewer events. Obviously, the tongue and soft palate are in a more favorable position when you sleep supine. Abdominal compression via sleeping prone may have different mechanical effects on the upper airway then those which occur when sleeping supine.

A problem with my study is that I have no direct measurements of diapgragm position and it's resulting interactions with the lungs, trachea and upper airway following abdominal compression. I can only assume the diaphargm went upwards towards the head with abdominal compression. What effect this has on upper airway tension is not known either. A great study would be to image the lungs, trachea and the upper airway to see what's happening to the structures when in different postures.

-SWS · Post by **-SWS** » Sat Oct 09, 2010 9:17 am

NotMuffy wrote:
-SWS wrote:However, if you want to increase readership, the subject line needs to be reworked to something like: Subject: Did Occult/Repressed Sex Drive Confound Our Squished Belly AHI Results???
Maybe we can work Gloria into the header.

Ahhhh, Gloria...

Oops! My oversight... Okay:

Subject: Did Gloria's Occult/Repressed Sex Drive Confound Our Squished Belly AHI Results???
https://www.youtube.com/watch?v=Xi2EgyZo2Pw

Please continue with those MUCH more on-topic contributions than mine... Although Gloria once stopped by around midnight and squished my belly. So we're back on topic already it would seem...

NotMuffy · Post by **NotMuffy** » Tue Oct 19, 2010 5:12 am

BTW, your oximetry is like Flintstone:

You're acquiring at 1 Hz (you need to be sucking up at 16) and your values are rounded out to a full % (at the 0.5s) instead of doing 0.1s.

You got a guy with a notepad manually entering data? You need a cable and some electricity?

Do you have indoor plumbing?

Rogue Uvula · Post by **Rogue Uvula** » Tue Oct 19, 2010 9:48 am

As a fifty-something with a gut, but not extremely overweight (240lb at 6'-2"), I can tell you I become short of breath very quickly when I squat down. Since this scenario bypasses any sleep variables, it seems entirely reasonable to believe I am constricting lung expansion, by pushing some of this gut up, into my diaphragm.
Doesn't it seem reasonable that by lying down, gravity is no longer generously pulling the "gut mass" away from the diaphragm and breaths would tend to be more shallow, resulting in a tendency towards hypopnea?

tattooyu · Post by **tattooyu** » Tue Oct 19, 2010 10:45 am

Rogue Uvula wrote:As a fifty-something with a gut, but not extremely overweight (240lb at 6'-2"), I can tell you I become short of breath very quickly when I squat down. Since this scenario bypasses any sleep variables, it seems entirely reasonable to believe I am constricting lung expansion, by pushing some of this gut up, into my diaphragm.
Doesn't it seem reasonable that by lying down, gravity is no longer generously pulling the "gut mass" away from the diaphragm and breaths would tend to be more shallow, resulting in a tendency towards hypopnea?

First, awesome avatar!

Second, I completely agree. I am 37, 5' 6" and weigh 200 lbs. I have a 38" waist. Even sitting in my office chair, I feel it's more work to breathe, especially when I wear snug-fitting jeans. However, it varies from day to day. When I stand up, or sit comfortably on a couch, it's much easier to breathe.

split_city · Post by **split_city** » Tue Oct 19, 2010 11:37 am

NotMuffy wrote:BTW, your oximetry is like Flintstone:

You're acquiring at 1 Hz (you need to be sucking up at 16) and your values are rounded out to a full % (at the 0.5s) instead of doing 0.1s.

You got a guy with a notepad manually entering data? You need a cable and some electricity?

Do you have indoor plumbing?

We've discussed that oximeter signal before. We have two probes attached. That (poor) signal is from the ear, the other attached to the finger. The one from the finger is used for scoring. It's acquired from compumedics. You know how to split the compumedics sats signal to Windaq?

Gotta go. Off to NZ for a conference. Be back on Sunday

NotMuffy · Post by **NotMuffy** » Tue Oct 19, 2010 5:15 pm

split_city wrote:That (poor) signal is from the ear, the other attached to the finger. The one from the finger is used for scoring. It's acquired from compumedics. You know how to split the compumedics sats signal to Windaq?

But the SaO2 from Compumedics was collected at 1 Hz as well:

What am I supposed to look for if I convert it to WinDAQ?

NotMuffy · Post by **NotMuffy** » Wed Oct 20, 2010 3:15 am

This results in the SaO2 signal recording only whole numbers again:

Anyway, my point is, in this patient, who's more like a UARS patient (especially if one used the 2008 4A Hypopnea Rule), how many desats are missed because "rounding" of the high/low oximetry values result in missing the minimum desat (3%) level (desats are not listed in the report)?

NotMuffy · Post by **NotMuffy** » Wed Oct 20, 2010 5:23 am

A closer look at respiratory events reveals that many hypopneas are central in nature:

With a lack of increased activity in the Poes channel during this event (an increased downward deflection would indicate attempting to inhale against obstruction), and rather, an actual decrease in the downward deflection, this event is central in nature.

Consequently, in this patient, anyway, "squishing the belly" simply destroys sleep continuity.

Do you have a better example? Maybe somebody with some frank obstructive apneas?

NotMuffy · Post by **NotMuffy** » Thu Oct 21, 2010 3:33 am

In trying to assimilate this data, I have a couple more questions:

This patient seems to have spent the whole night on his right side. Was that planned (i.e., patient on side = less effect of abdominal contents on diaphragm at baseline)?

OTOH, it seems to me that there's a pile of information missing if you're not looking at the airway in the supine position while all this is going on.

Did you measure Lung Volumes (especially FRC) during changes in cuff pressures (prior to NPSG) in this state (on right side)(or better yet, right, left (account for the heart) and supine)?

Again, looking at that area of stable sleep (even while excluding SWS) it seems to me that this guy's biggest problem isn't "SDB", it's "S".

split_city · Post by **split_city** » Sun Oct 31, 2010 1:05 am

NotMuffy wrote:
split_city wrote:That (poor) signal is from the ear, the other attached to the finger. The one from the finger is used for scoring. It's acquired from compumedics. You know how to split the compumedics sats signal to Windaq?
But the SaO2 from Compumedics was collected at 1 Hz as well:

What am I supposed to look for if I convert it to WinDAQ?

Sorry for the late reply. I was busy with the NZ conference and also submitting other abstracts, travel awards etc.

Thanks for pointing out the sats sampling rate issue. I will check up on that.

split_city · Post by **split_city** » Sun Oct 31, 2010 1:08 am

NotMuffy wrote: Do you have a better example? Maybe somebody with some frank obstructive apneas?

I'll have to have a look. My aim was to only recruit patients who were diagnosed with mild-moderate OSA as we thought that abdominal compression would have little impact in those patients with severe OSA.

split_city · Post by **split_city** » Sun Oct 31, 2010 1:31 am

NotMuffy wrote:In trying to assimilate this data, I have a couple more questions:

This patient seems to have spent the whole night on his right side. Was that planned (i.e., patient on side = less effect of abdominal contents on diaphragm at baseline)?

This patient actually ws studied in the supine posture. There was no position sensor attached so it remained in its default state. We did study some patients on their side (either left or right). The initial aim was to study only those patients in the supine posture. However, we were finding it difficult to find patients who fit the AHI criteria e.g. while some patient's overall AHI was between 15-45, their OSA was much worse when they slept supine. So we changed our inclusion criteria to include anyone who had an AHI between 15-45 in at least one posture (supine or lateral) in which they spent at least 30mins of sleep during their diagnostic study. While obviously posture may be a confounding factor, we still believe the mechanics are the same i.e. squishing the stomach will still elevate the diaphragm and reduce tension on the airway, regardless of whether the patient slept supine or laterally. This is still something we will have to discuss in the methodological consideration section.

There is missing data in the example you put up (SWS stuff). Patient's were asked to buzz us if they wished to switch positions. We unplugged the pneumotach when they moved and we didn't analyze this data.

NotMuffy wrote:Did you measure Lung Volumes (especially FRC) during changes in cuff pressures (prior to NPSG) in this state (on right side)(or better yet, right, left (account for the heart) and supine)?

Yes we used magnetometers to measure changes in FRC with compression. We measured A-P and lateral dimensions of the chest and abdomen. I haven't analyzed this data yet and it's going to take a bit of work. In a perfect world, we would have liked to measure absolute FRC. This is in the "too hard basket" as this stage unless we get patients to sleep in a body box.

NotMuffy wrote:Again, looking at that area of stable sleep (even while excluding SWS) it seems to me that this guy's biggest problem isn't "SDB", it's "S".

Unlike you, not everyone can sleep with all the equipment attached. Sleep quality, even with the cuff deflated wasn't ideal, but that's what you have to expect with a study like this

But yes, the question of sleep quality with cuff inflation might be an issue. That's one reason why we only had 10 min periods.

Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI

Re: Squishing the belly increases AHI