SH chart - what is happening here?

[Jay Aitchsee]

Wouldn't that show up as a leak on the leak chart? Her is some of my flow. Is it the same? or different? I seek to be educated here. This flow had no flow restrict or leak show up with it either.
educateme.png

It looks to be the same or similar.

And yes, I would think you should see some leak result, but not necessarily huge. Leaks are reported in L/min as are Minute Ventilation (Volume). Typical Minute Ventilation while sleeping is around 8L/min. If none of this normal expiration was being sensed and measured, i.e, all exhalation through the mouth while using a nasal interface, then the calculated leak would be equal to the calculated Minute Ventilation, or around 8L/min.

Check your leak line (adjust the Y scale if necessary) and see if there is not a corresponding leak with your "abnormal" Flow Rate wave.

I think it should be noted that mouth leaks can occur throughout the respiratory cycle (during inhale as well), in which case, the calculated leak could be greater.

[Spot123]

Hmm. I'm thinking it could it be a leak elsewhere besides mouth? But I don't recall a leak that night. Although I see a very low leak on the leak chart.
I have a history of grinding my teeth so don't think an open mouth is a typical problem for me.
This chart in question is from Tuesday, which would have been the 3rd or 4th night since I switched to nasal pillow, so possibly the night I woke in the dark with a slightly dry mouth on one side. It was not as bad as I've had before so I gulped some saliva and went back to sleep. So I guess either is a possibility.

But I will say that I've opened my mouth with the machine on the last couple of mornings, just to see what it would feel like and felt all sorts of weird pressure building/blowing around inside my head. I have not had that feeling at night so if it was a mouth leak, it would have been very low.

[Miss Emerita]

“Typical Minute Ventilation while sleeping is around 8L/min.” What I’ve read suggests that resting MV of 8 would be on the high side. Here is some information from U. Michigan (MV) and U. Indiana (TV):

Minute Ventilation. During quiet breathing at rest, an adults" breathing rate averages 12 breaths per minute (about 1 breath every 5 s), whereas tidal volume averages about 0.5 liter of air per breath. Under these conditions, the volume of air breathed each minute (minute ventilation) equals 6 liters.
Minute ventilation (VE) = Breathing rate x Tidal volume
6.0 L•min–1 = 12 x 0.5 L

Tidal volume. The tidal volume is the amount of air inspired (or expired) during normal tidal breathing. At rest, tidal volume in healthy adult men is approximately 500 ml, and about 400 ml in women. Tidal volume increases with activity to accommodate increased need for gas exchange.

[Jay Aitchsee]

Hmm. I'm thinking it could it be a leak elsewhere besides mouth? But I don't recall a leak that night. Although I see a very low leak on the leak chart.
I have a history of grinding my teeth so don't think an open mouth is a typical problem for me.
This chart in question is from Tuesday, which would have been the 3rd or 4th night since I switched to nasal pillow, so possibly the night I woke in the dark with a slightly dry mouth on one side. It was not as bad as I've had before so I gulped some saliva and went back to sleep. So I guess either is a possibility.

But I will say that I've opened my mouth with the machine on the last couple of mornings, just to see what it would feel like and felt all sorts of weird pressure building/blowing around inside my head. I have not had that feeling at night so if it was a mouth leak, it would have been very low.

Well, as I pointed out above, a leak only from the mouth and only on exhale would only be about 8L/min, or less. What does your line indicate? Put the cursor over it and it will read out at the top left of the leak chart. It could be a leak from somewhere else, but the machine is sensing very little flow from your nose on exhale. If the leak were somewhere else, likely there would be more exhalation flow shown.

As far as the feeling goes, if you were inhaling thru your nose and exhaling through your mouth, it may not of felt weird if the soft palate stopped the inflow from the machine on exhale (Which it looks like it did). It really shouldn't feel much different than breathing in through the nose and out through the mouth while not wearing a cpap. Try it. And, most people can exhale easily through clenched teeth. Try that, too. It's one of the reasons chin straps are often ineffectual.

Remember, the machine can sense flow only through the hose, which, in the case of a nasal interface, is connected only to the nose. If one breathes in and out through the mouth while wearing a nasal interface, the machine will not detect any breaths and will score an apnea if the condition continues longer than 10 sec.

[Jay Aitchsee]

“Typical Minute Ventilation while sleeping is around 8L/min.” What I’ve read suggests that resting MV of 8 would be on the high side. Here is some information from U. Michigan (MV) and U. Indiana (TV):

Minute Ventilation. During quiet breathing at rest, an adults" breathing rate averages 12 breaths per minute (about 1 breath every 5 s), whereas tidal volume averages about 0.5 liter of air per breath. Under these conditions, the volume of air breathed each minute (minute ventilation) equals 6 liters.
Minute ventilation (VE) = Breathing rate x Tidal volume
6.0 L•min–1 = 12 x 0.5 L

Tidal volume. The tidal volume is the amount of air inspired (or expired) during normal tidal breathing. At rest, tidal volume in healthy adult men is approximately 500 ml, and about 400 ml in women. Tidal volume increases with activity to accommodate increased need for gas exchange.

Thank you, Miss.

I just took a stab at it from memory. If the poster's MV was but 6L/m, then the associated leak calculated due to mouth exhale would ony be about 6L/min. In any event, these metrics vary by individual and thoughout the night. Spot MV can be seen by examining the SleepyHead MV chart.

The point I was trying to make was that the leak associated with a mouth exhale could be relatively minor.

[palerider]

Wouldn't that show up as a leak on the leak chart? Her is some of my flow. Is it the same? or different? I seek to be educated here. This flow had no flow restrict or leak show up with it either.
educateme.png

It looks to be the same or similar.

And yes, I would think you should see some leak result, but not necessarily huge. Leaks are reported in L/min as are Minute Ventilation (Volume). Typical Minute Ventilation while sleeping is around 8L/min. If none of this normal expiration was being sensed and measured, i.e, all exhalation through the mouth while using a nasal interface, then the calculated leak would be equal to the calculated Minute Ventilation, or around 8L/min.

I'm pretty sure it doesn't work that way.

Leaks are measured based on the total volume of air that flowa out of the machine, not with a "hey, where did some of that air go?"

I'd have to experiment to say for certain.... But I'm pretty sure.

Edit: I'm at least somewhat wrong, pure mouth exhales do show up on the leak chart.

[palerider]

Hmm. I'm thinking it could it be a leak elsewhere besides mouth? But I don't recall a leak that night.

You don't recall, because you were asleep.

If the leak we're somewhere else, you'd see normal respiration on the flow line, and higher leak.

The only way you'd get a result like you have is if that leak started and stopped in perfect time, and amount with your exhalations.

[Jay Aitchsee]

Wouldn't that show up as a leak on the leak chart? Her is some of my flow. Is it the same? or different? I seek to be educated here. This flow had no flow restrict or leak show up with it either.
educateme.png

It looks to be the same or similar.

And yes, I would think you should see some leak result, but not necessarily huge. Leaks are reported in L/min as are Minute Ventilation (Volume). Typical Minute Ventilation while sleeping is around 8L/min. If none of this normal expiration was being sensed and measured, i.e, all exhalation through the mouth while using a nasal interface, then the calculated leak would be equal to the calculated Minute Ventilation, or around 8L/min.

I'm pretty sure it doesn't work that way.

Leaks are measured based on the total volume of air that flowa out of the machine, not with a "hey, where did some of that air go?"

I'd have to experiment to say for certain.... But I'm pretty sure.

Yes, please do (experiment). I have.

And you are right, of course, total volume and rate of flow. I'm pretty sure when I have conducted the experiment the result was as I described. However, I could be wrong. I am occasionally

I'll try to find my data to verify, meanwhile, why don't you try it. We're looking to set up with no mask leaks, nasal inhale and oral exhale. And I think it takes a certain amount of time to produce valid calculations.

[palerider]

I do have a leakless mask available

[Jay Aitchsee]

I realize this is not definitive, but it does lend credence to my supposition:
Note the 8 L/min leak during the nose in, mouth out segment

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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viewtopic/t114197/Flow-Rate-Waveform-Ex ... l#p1104979

[Jay Aitchsee]

So here's my experiment from last night for your consideration, PR. It wasn't as controlled as I'd like and while it doesn't show that leak equals MV as I suggested, it does show the two are related. Perhaps not being able to hold the exhale at the zero level skews the results?
Three periods of mouth exhalation with nominally decreasing leak values from left to right corresponding to nominally decreasing MV values. Leak values of 7.8, 7.2, and 6.0 compared to MV values of 6.0, 5.3, and 5.2 respectively, the difference between Leak and MV being close to a constant 1.8.
Edit: Or, the 1.8 difference could be due to vent rate. See discussion below. I'm using the N30i for this.

leakvsMV.JPG

[katestyles]

So here's my experiment from last night for your consideration, PR. It wasn't as controlled as I'd like and while it doesn't show that leak equals MV as I suggested, it does show the two are related. Perhaps not being able to hold the exhale at the zero level skews the results?
Three periods of mouth exhalation with nominally decreasing leak values from left to right corresponding to nominally decreasing MV values. Leak values of 7.8, 7.2, and 6.0 compared to MV values of 6.0, 5.3, and 5.2 respectively, the difference between Leak and MV being close to a constant 1.8. leakvsMV.JPG

I love science!

[katestyles]

So - question. Here is a section of my flow from last night.

screenshot-20190316-105525.png (139.34 KiB) Viewed 905 times

I see the waveform that says I have no exhalation through the machine. I am using the bleep mask- so any leak has to be mouth, not mask. There is no leak recorded, not even the 8L/m. Does this match the flat line of a "fake" apnea that you created by breathing solely through the mouth? Am I mouth exhaling? If I am, there should be a leak according to Jay's experiment.

[Jay Aitchsee]

I'm going to guess here that the ResMed adjustment for mask vent is hiding the leak. ResMed subtracts a value from the flow based on the machine mask setting to account for mask venting in determine leaks. If the actual vent rate of the mask used is much lower than that for the setting used, it will mask small leaks. I have no clue what the vent rate is for the bleep, perhaps it can be found in the documentation that came with the mask.

ResMed mask vent rates are around 37 L/min at 10-12 cmH2O pressure.
https://www.resmed.com/us/dam/documents ... er_eng.pdf

[Pugsy]

I have no clue what the vent rate is for the bleep, perhaps it can be found in the documentation that came with the mask.

I did an experiment using some really high pressures while awake...no leak at all...using Respironics so I could see the total leak/vent rate and it's extremely small at high pressures....like less than 25 L/min

I didn't get any official paperwork with my product but the vent rate is available at the website under a downloadable brochure.