Need Help from a ResScan Graph Expert

[fredn]

Hello again ....

I'm still going over my Graphs picking up what I can in understanding all of the details they provide. I'd like someone that is VERY Knowledgeable with these graphs to tell me if I'm right or wrong in what I believe is going here.

Here's the section of a chart that I'd like to start with ...



What I am trying to do is understand what is going on at the time of the pictured obstruction

OK ... so take a look at the flagged obstruction. It took place a approx 22:08:46 ....and it lasted for 27 seconds.

The Obstruction flag is placed at "THE END" of the obstruction ... when it cleared. It would have to be otherwise there is no way of knowing the duration (27 seconds)

So look to the left of the obstruction flag .... on the "FLOW" graph .... at approx 22:08:18 I began to inhale. Show by the flow moving in a positive direction (upwards)

At approx 22:08:20 ... flow goes flat line ... this is where the obstruction begins .... it stay flat until approx 22:08:46 ... where the obstruction clears so the flow (inhale) picks up again .... hence the line again moving in a positive direction.

Note that 22:08:20 till 22:08:46 is 26 seconds .... just about the 27 seconds reported ....

There are no significant leaks at this time to explain the no change in "sensed flow" ....

So .... do I have it right so far? I'm asking this because of something else that I am seeing .... and my "deduction" is not correct if what I thought took place isn't true.

I'll post the next part tonight .... after I find out if I'm right so far.

Thanks for the help ... Fred

[Pugsy]

Looks to me like your reasoning is sound.
I couldn't really understand if there was a question in your thoughts.
Obstructive events don't always have to be 100% reduction in air flow...there can be some air movement still going on.
Looks to me like the tidal volume is maintained through a majority of the recorded event and only finally gives up the ghost nearing the end of the flagged event.
Does the sudden drop indicate the beginning of breathing on your own and thus the end of the apnea?

[fredn]

Looks to me like your reasoning is sound.
I couldn't really understand if there was a question in your thoughts.
Obstructive events don't always have to be 100% reduction in air flow...there can be some air movement still going on.
Looks to me like the tidal volume is maintained through a majority of the recorded event and only finally gives up the ghost nearing the end of the flagged event.
Does the sudden drop indicate the beginning of breathing on your own and thus the end of the apnea?

Hi Pugs ....

I just wanted to make sure I was reading things right ... the reason why is if I look at my "pressure graph" for the same period of time I am NOT seeing an increase ... which I "thought" I should if the machine was trying to "get past" the obstruction. I'm at work now so I can't upload anything or even look at anything else.

I'll be home in around 5 hours and I'll get everything uploaded then .... Shouldn't I see an increase in pressure at that time?

Fred

[Pugsy]

the reason why is if I look at my "pressure graph" for the same period of time I am NOT seeing an increase ... which I "thought" I should if the machine was trying to "get past" the obstruction. I'm at work now so I can't upload anything or even look at anything else.

I'll be home in around 5 hours and I'll get everything uploaded then .... Shouldn't I see an increase in pressure at that time?

Ahh, that's the question...why no pressure increase seen when there is an obvious reduction in flow?

These machines are designed to respond to the warning signs of an impending apnea event...snores and flow limitation with an increase in pressure.
If an event sneaks past the defenses (like maybe didn't have any warning signs..comes in out of the blue quickly) the machine can't/won't respond.
Once an event is actually in progress these APAP machines just sit by and twiddle their thumbs. They can't/won't try to blow through the obstruction...that would be working like a ventilator and these machines don't do that. That belongs to the ASV category of machine.

This is why we need a decent effective minimum pressure in some form...hopefully to prevent these sudden out of the blue apnea events...we can't stop them all so a few random "frank" apneas we just sort of ignore. We can't expect to prevent every single apnea that might happen unless we want to use extremely high pressures all the time to hold the airway open and even then I am not sure everything would be prevented.

So these machines with auto adjusting pressures aren't designed to respond just to the event itself. They respond to event precursors (warning signs) instead. Once an event is actually happening...they simply won't respond at all..they sit back and twiddle their thumbs waiting for it to end and then they re-evaluate things. It's the way the algorithm is designed.
They aren't ventilators and simply can't do it. If you ever see a pressure increase right at the time of a full grown apnea event...it is because of a snore or flow limitation being sensed. It's doubtful that you will ever see that happen very often if at all.

So your graphs show the machine doing what it is designed to do. Nothing to worry about. No malfunction.
Now if you see a lot of these obstructive type of events....that's when adjustments are made in the lower pressure settings..in your case EPAP...in the case of someone using APAP machine then we would increase the minimum a bit in hopes of doing a better job of preventing the collapse.

The whole idea is prevention of the situation where a collapse of the airway occurs....and not "fixing" an event by blowing the airway open with more pressure.

[fredn]

Pugsy,

I'm so glad you're on this Board .... I had nightmares about "How am I gonna find someone that not only knows this crap but is willing to take time to explain it" ..... something tells me this was gonna be over the head of my Respiratory Therapist FOR SURE and maybe even my Sleep Doctor.

Tonight will be my 7th night ..... I don't think compliance will be an issue .... I'm doing 7-8 hours per day ..... feeling pretty darn good .... on the verge of feeling like I've had extra cups of coffee without drinking any extra .... I'm even getting thing done on my "Honey Do" list .....

Fred

[Pugsy]

When you get through your Honey Do list...I have a few things on mine.

There's a lot more I could have gone into about the algorithm and how and why these machines do what they do but I tried to keep it as simple as I could and I am short on time this morning.

All of what I have said I gleaned from old posts where the guys that really had studied the algorithms had explained it.
Lots of reading and re-reading of stuff till I could wrap my brain around what was being said.

Frank apneas (any kind) coming out of the blue can happen and we have to shrug our shoulders and move on unless there are too many of them. Remember even people without the OSA diagnosis can and will have a an occasional apnea...they just don't have as many of them as we do so they don't present much of a problem.

Often people think these machines work like ventilators....they don't and can't. They can't deliver enough pressure to blow the airway tissues open even if they wanted to.
It's all about prevention and not about "fixing" once something gets broken or in this case collapsed.

[khauser]

All of what I have said I gleaned from old posts where the guys that really had studied the algorithms had explained it.
Lots of reading and re-reading of stuff till I could wrap my brain around what was being said.

What would you suggest I look for to find these posts? I am an intensely curious person by nature, and techy.

[Pugsy]

What would you suggest I look for to find these posts? I am an intensely curious person by nature, and techy.

Man.....that was probably back in the summer and fall of 2009. Back when I was spending hours and hours a day reading all sorts of stuff.
I would just start reading posts and go to links and read some more.

I can't even say search through my posts because most of the time I didn't comment.

I am short on time today...later when I have time maybe I can look back and see if something stands out that would help.
A lot of the posts were from SWS so you might search his posts.
Might search for discussions about algorithms...find a thread with a lot of discussion and see if it contains useful information or not.
It's hit or miss though.

Mainly it was just read every post I could and as the weeks and months went by some of the information stuck.
On days when the forum was slow...I would just go back through the old days with unread stuff and pick stuff that sounded interesting. I would spend hours and hours reading every day.

Unfortunately not any one source that had all the good stuff in one location.

[DoriC]

Look through posts by Rested Gal, Wulfman, Robysue, Delta Dave,(and his aliases Muffy and NotMuffy), Hawthorne and I know there are many other "experts" that really know their stuff! I've learned so much from all of them. I'll probably be adding you to the list pretty soon!

[idamtnboy]

OK ... so take a look at the flagged obstruction. It took place a approx 22:08:46 ....and it lasted for 27 seconds.

The Obstruction flag is placed at "THE END" of the obstruction ... when it cleared. It would have to be otherwise there is no way of knowing the duration (27 seconds)

So look to the left of the obstruction flag .... on the "FLOW" graph .... at approx 22:08:18 I began to inhale. Show by the flow moving in a positive direction (upwards)

At approx 22:08:20 ... flow goes flat line ... this is where the obstruction begins .... it stay flat until approx 22:08:46 ... where the obstruction clears so the flow (inhale) picks up again .... hence the line again moving in a positive direction.

Note that 22:08:20 till 22:08:46 is 26 seconds .... just about the 27 seconds reported ....

You pretty much have it. Don't get wound up about where the apnea flag is with respect to the end of the apnea. There are some data recording oddities in the S9, or at least used to be unless the newer ones have fixed them. The flag can appear several seconds before or after the flow restarts. This has to do with the processing time and recording time of the S9. The data does not record an actual time stamp. What is recorded is the date and time a particular file was started, and then an elapsed time from there to the event. For whatever reason the S9 sometimes has a significant variation in the record start times for the various files. Second, I have never been able to determine where exactly on the flow curve the start and end times are tagged for an apnea so it's pretty much futile to correlate exactly what you see on the flow graph with the duration number on the flag. Also, the flow curve is recorded at 25 times per second, but the duration is recorded in whole seconds. You are going to see rounding errors between the graph and flag. The flow and flags are in two different data files.

You see the small saw tooth in the pressure graph during the apnea? That is the flow oscillation the S9 uses to determine if an apnea is a central, or open airway, or an obstructive apnea. It also starts a few seconds after the flow stops.

As Pugsy has said, the S9 in APAP mode changes pressure after the fact in response to obstructions and flow limitations. The more often and closer the apneas the more the pressure goes up. Then, after a period of no apneas it starts ramping down. There are some discussions in the literature that continued use of APAP is not good. A good CPAP pressure setting is somewhere near the 95 percentile level of the APAP mode. Then it can be adjusted as you have seen discussed here in many threads.

Since you are new, here is one bit of advice. Be patient! This process of apneas and avoiding them is extremely variable. DO NOT place credence in changes from one night to the next. Watch the average trends over many days and look for changes over weeks and months. Night to night variations can be incredibly extreme at times. Why? No one knows. That's just the way we're made!

[mollete]

So look to the left of the obstruction flag .... on the "FLOW" graph .... at approx 22:08:18 I began to inhale. Show by the flow moving in a positive direction (upwards)

Negative [insert chuckle here]. Everything above the red line is inhalation, below exhalation. Consequently, at approx 22:08:18 you are not begining inhalation, you are at peak exhalation.

Also, "IMHO", the apnea is exactly 27 seconds.

[fredn]

So look to the left of the obstruction flag .... on the "FLOW" graph .... at approx 22:08:18 I began to inhale. Show by the flow moving in a positive direction (upwards)

Negative [insert chuckle here]. Everything above the red line is inhalation, below exhalation. Consequently, at approx 22:08:18 you are not begining inhalation, you are at peak exhalation.

Also, "IMHO", the apnea is exactly 27 seconds.

Me thinks you are "splitting hairs" ..... in either case I am done with exhale and beginning inhale .....

Fred

[mollete]

Well, you asked:

I'd like someone that is VERY Knowledgeable with these graphs to tell me if I'm right or wrong in what I believe is going here.

[idamtnboy]

One thing I have found kind of fascinating when you look at the flow graphs is how the flow rate during inhale is so different from exhale. Inhale is often a smooth up, over, and down curve, while exhale is fast for awhile and then tapers off to no flow just before the next inhale begins.

[mollete]

I would think mostly because inspiration is active and expiration is passive, resulting in a (normal) I:E Ratio of 1.0 : 1.5 - 2.0.