Flow Rate Waveform Examples using a Nasal Mask

[Jay Aitchsee]

Consolidated From Other Threads as Indicated

Nasal Mask Waveforms: viewtopic.php?f=1&t=113502&p=1095402#p1095379

This image contains examples of the various kinds of breathing that can be done while wearing a Nasal Mask. Flow Rate waveforms generated while wearing a nasal mask can be confusing. Flow Rate is just that, the machine is measuring the Rate of Flow past the sensor which is located in the machine remotely from the patient. With a nasal mask, the only Flow the machine can measure directly is that which flows through the hose into or out of the nose. Flow that enters or leaves the lungs by way of the mouth can not be measured directly because the hose is not attached to the mouth. So with a Nasal Mask, Flow Rate means Nasal Flow Rate, we are looking at the Nasal Flow (which BTW, includes leaks through the nose and out the mouth, or around the edges of the mask).
Below we see how the inability to directly sense mouth flow affects the shape of the Flow Rate Waveform. The sample is about 8 minutes long, done when I was awake and runs through a series of nasal/oral breathing combinations. The zoomed portions are about 1 minute in length and run consecutively starting at about 16:15 to about 16:20.

• From the top, in order:
  • Flow Rate : The Sample Segment
    Flow Rate 1: Nose In, Nose Out; Normal Breathing;
    Flow Rate 2: Nose In, Mouth Out; Commonly seen
    Flow Rate 3: Mouth In, Mouth Out; Flat line. The machine is unable to sense approximately 12 breaths and scores a 47 second apnea. Occasionally seen as a break in therapy.
    Flow Rate 4: Mouth in, Nose out; seen often as a flat line between two exhales, an inhale by mouth.

• From the top, in order:
  • Flow Rate : The Sample Segment
    Flow Rate 1: Nose In, Nose Out; Normal Breathing;
    Flow Rate 2: Nose In, Mouth Out; Commonly seen
    Flow Rate 3: Mouth In, Mouth Out; Flat line. The machine is unable to sense approximately 12 breaths and scores a 47 second apnea. Occasionally seen as a break in therapy.
    Flow Rate 4: Mouth in, Nose out; seen often as a flat line between two exhales, an inhale by mouth.

Sleep Wake Junk: viewtopic.php?f=1&t=113409&st=0&sk=t&sd=a#p1094245

People often ask, "what about all these CAs?" And the reply is often that it looks like Sleep Wake Junk (SWJ). Sleep Wake Junk is characterized by irregular Flow Rate waveforms followed by a CA's or sometimes OA's. It is most often seen in the early morning hours.
Some examples below. These are NORMAL waveform segments. The the OA's and CA's would not count toward AHI in a lab sleep study.




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Below is an example of a disturbance or arousal of unknown origin.
The machine scored a 16 second Obstructive Apnea (OA); however, we can see that there is sharp increase and irregularity in the Flow Rate Waveform immediately preceding the event, indicating a likely arousal. Additionally, we can see that the pulse rate and the oxygen level actually increase during the event. With an actual OA, it would be typical to see the O2 fall during the event and then rise with an increase in pulse after.
Likely, I changed positions or rolled over and held my breath for 16 seconds while doing so. The small break in the Pulse Oximeter trace reinforces the supposition that this was movement related.
This event would not be scored as an OA in a lab sleep study.




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CA Examples:

Mouth Leaks with a Nasal Mask: viewtopic.php?f=1&t=112758&p=1085906#p1085906

Flow wave examples of mouth breathing wearing a nasal mask:
23:43:30 to 23:44:00 Normal Breathing; Nose In, Nose out.
23:44:00 to 23:44:44 Total Mouth Breathing; Mouth in, Mouth out. 44 second apnea scored at resumption of nasal breathing, no leaks scored.
23:44:50 to 23:45:20 Exhalation by Mouth: Nose in, mouth out, scoring a leak of about 8L/min

Note: With a nasal mask, Flow is only that which passes through the hose connected to the nose. The machine can not directly measure any flow through the mouth. The machine determines leak by measuring the outflow compared to the inflow. If outflow is greater than inflow, ignoring mask vent rate, there is a leak. When exhaling through the mouth, some outflow is lost (to the hose) and the machine scores a leak. When inhaling through the mouth, inflow from the machine is reduced or stopped and the machine registers an apnea.

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Below:
Normal sleep breathing on top, expiratory mouth breathing on the bottom in large leak (shaded area)
Notice the flattening of the expiratory portion of the wave with exhalation by mouth.

Edit: Times corrected

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Knowing whether leaks are from the mouth or mask could be helpful. The sample below contains two sets of flow waves from the same night taken during periods of over threshold high leak as indicated by the shade. The expiratory portion of the top set has the rapid rise and relatively flat run typical of a mouth leak. The bottom sample does not.
Since the over threshold leak is present with or without mouth leaks, I can assume it to be a mask leak and my pillows or headgear need attention.


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Classic mouth leak plateau shaped waveforms



Mouth Leaks Defined: Patent Application

In some cases, pressurized air flows through the velopharyngeal sphincter (i.e. between the lateral pharyngeal walls and the soft palate) into the oral cavity and then out through the lips, resulting in a mouth leak. When a mouth leak occurs, pressurized air does not reach the lungs and does not contribute to ventilation, thereby rendering the treatment less effective or ineffective. In addition, because of the one-way airflow through the nasal passages, mouth leaks tend to dry the mucosal surfaces resulting in nasal congestion after only several hours of use. In some applications, the CPAP system will apply a higher pressure through the nose mask when a mouth or mask leak is detected to compensate for the leak which only exacerbates the problem. In many cases, the side effects are often so severe that the patient is no longer able to tolerate treatment.

[Grace~~~]

W W!!!

I just got home and checked CPAPTALK (man has *my* life changed)
and saw this wonderful thread ~~~

Thank you so MUCH for posting this thread, Jay.

I cannot wait to try and comprehend it.


I did quickly skim the pictures and didn't see my brand of ugly at first glance but I will really try and work
on understanding everything that is here.

~~~exhausted after a rough day and might need to start fresh in the morning.

So exciting!

THANK Y U

so would xoxoxox be too much?

[Jay Aitchsee]

so would xoxoxox be too much?

No, just right

I did quickly skim the pictures and didn't see my brand of ugly at first glance

I think many people's brand of ugly is really wake breathing, which is very irregular. Wake breathing while on a machine will produce many false events. False because events only count when we are asleep. Have a look under the Sleep Wake Junk heading above. These examples include wake breathing, like from 04:46:30 to 04:50:30 in the top chart and 06:00:40 to 06:03:30 in the bottom.

[zack243]

Thank you for all your obvious work and time. Your thread has greatly helped me understand my personal wave forms. This is an amazng amount of information in one dedicated post!

Now if I can only figure out how to save this.

Zack

[avi123]

Jay, I am using a nasal mask. What do I need to know from your examples and why is it important?

[Jay Aitchsee]

Avi, thanks for your response. I don't have time, now, to engage in a long discussion about the waveforms. I am leaving for an extended trip. Just let me say that an understanding of the Flow Rate Detail could help one decide what type of remedial action should be taken, if any.

For example, contrary to what you posted here: viewtopic.php?f=1&t=113723&p=1098817&hi ... h#p1098793, "The only way we can tell if a leak is a "mouth leak" is by the shape of the Leak graph", the shape of the flow wave will also yield a clue, as in this example from above:

Knowing whether leaks are from the mouth or mask could be helpful. The sample below contains two sets of flow waves from the same night taken during periods of over threshold high leak as indicated by the shade. The expiratory portion of the top set has the rapid rise and relatively flat run typical of a mouth leak. The bottom sample does not.
Since the over threshold leak is present with or without mouth leaks, I can assume it to be a mask leak and my pillows or headgear need attention.

Additionally, knowing where CA's are falling in relation to flow wave distrubances could help decide what action to take. Are they a result of arousals? Or, are they truly central in nature? As in this example:

CA Examples:

[Grace~~~]

Hello Jay ~~~

I had not seen this video until today and I thought it would be nice linked in to
this thread.

also, watch this: https://www.youtube.com/watch?v=-gie2dhqP2c
(copied from palerider)

I am sure most who have been around here awhile have seen it, but maybe
newbies like *me* have not?

*I* was on the edge of my seat.
Poor sleep disordered model! (in video)
I felt terrible watching the struggle to breath.
...and worse when I saw what it made his flow rate chart look like

..but it ends with such a gorgeous family picture.
So "Happy Ending".



Thank you again for this educational thread, Jay.

~~~grace

[riley525]

Lots of great examples and that video was very educational as well. Thanks for posting this!!

[JimW159]

I had not seen this video until today and I thought it would be nice linked in to
this thread.
...watch this: https://www.youtube.com/watch?v=-gie2dhqP2c
(copied from palerider)

I, too, had not seen this until now. Overall, an excellent explanation of SDB in lay terms. It did raise a couple of questions for me, though. If this should fall into another thread, let me know and I will move it. Within the video, some sort of distress in the normal air flow pattern always corresponds to a change in the heart rate and produces some countervailing reaction. While an example only, I note the resting heart rate while sleeping to be in the 50-60 bpm range; during an apnea it drops significantly to the 40s. However, during the period following an hypopnea event the heart rate escalates to about 70bpm and following an OA, it raises to the 80s. The question these perambulations in heart rate raise for me is "what happens if these heart rate changes do not occur?" Specifically, if one has a pacemaker as I do the heart beats at a fairly regular rate, any lowering of the heart rate is met with a trigger to maintain the regular rate. AFAIK, any increase is met with a countervailing trigger that modulates the increase and keeps it fairly well regulated. Dramatic heart rate increases typically seen during exercise rarely occur with a pacemaker. While I am certain heart rate is a following characteristic of SDB and not a causative event, my questions are: Are there any changes in the reactions to distress events if the heart rate doesn't change appreciably? and if so, what are the net effect of these changes?