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Wisp mask - interesting leak results
#1
I picked up a Wisp from my DME on Friday, so now have just two nights of data, but something interesting is happening with the leaks. The Wisp is my ninth mask. For several months previously I used a Pilairo, which I still love for its comfort, but the leaks were typically near or above the maximum you are supposed to have. With the Wisp my leaks for Friday and Saturday nights were:

Min Med 95% Max
00.00 12.00 25.87 31.20
00.00 10.80 33.60 43.20

For the week preceding, using the Pilairo, the 95% leak rate was 50.16 and the Max leak rate was 55.20. It has been only two nights with the Wisp, but so far it is providing a significant improvement.

Now, here's the interesting part: The S9 Autoset is going to much higher pressure with the Wisp than it ever did with the Pilairo or any previous mask. I view this as excellent, because one of my complaints with both my S9 Autoset and my previous PRS1 is that they did not respond fast enough, and thus never gave me the pressure I really needed to avert an event.

My machine is currently set at 11-15. For the past two nights with the Wisp my pressures were:

Min Med 95% Max
11.00 13.22 14.78 15.00
11.00 12.64 14.50 14.96

The averages of the pressures for the preceding week with the Pilairo were:

Min Med 95% Max
11.00 11.64 12.40 12.47

In addition, looking at every night for the last two months with the Pilairo the 95% pressure never went above 13.10 and the Max never exceeded 13.65. It has been only two nights with the Wisp so far, but it sure looks as though the improvement in the leak amount has also improved the response of the machine.

Indeed, the fact that I hit 15.00 on Friday night tells me that I ought to bump the maximum up to 16, or maybe even more. I'm going to watch this for a week or so first, though. (My AHIs are still <2.0.)

I don't know why it did not dawn on me a long time ago that the leaks were probably why my machines were not going high enough. After all, gases can be compressed, and the pressure in the hose is all the machine really has to go on. The greater the leak the greater the "squishiness factor"*.

*A new scientific term that I just invented. You heard it here first! Smile
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#2
Hi JJJ, Interesting post, thank you.
I have seen adds for the wisp mask but I forgot if that is a nasal mask.
trish6hundred
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#3
(01-20-2013, 03:25 PM)trish6hundred Wrote: I have seen adds for the wisp mask but I forgot if that is a nasal mask.

Yes, the Wisp is brand new on the market. It is a nasal mask, not a nasal pillow mask. The online suppliers still list it as "coming soon," but my DME is a large organization and usually gets stuff before other suppliers. My respiratory therapist has had a Wisp to test himself for over a month.



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#4
(01-20-2013, 01:47 PM)JJJ Wrote: With the Wisp my leaks for Friday and Saturday nights were:

Min Med 95% Max
00.00 12.00 25.87 31.20
00.00 10.80 33.60 43.20

For the week preceding, using the Pilairo, the 95% leak rate was 50.16 and the Max leak rate was 55.20. It has been only two nights with the Wisp, but so far it is providing a significant improvement.
still leak is on the high side
try to add chinstrap
chinstrap can helps minimize mouth leaks




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#5
(01-20-2013, 01:47 PM)JJJ Wrote: Now, here's the interesting part: The S9 Autoset is going to much higher pressure with the Wisp than it ever did with the Pilairo or any previous mask. I view this as excellent, because one of my complaints with both my S9 Autoset and my previous PRS1 is that they did not respond fast enough, and thus never gave me the pressure I really needed to avert an event.

Hi JJJ,

Regarding pressure, the reason for higher presure with the Wisp might not be that the machine is responding faster. A possible reason may be unconscious changes in sleep position, such as the angle of your neck or if more time is now spent on your back, etc.

Quote:It has been only two nights with the Wisp so far, but it sure looks as though the improvement in the leak amount has also improved the response of the machine.

Part of the reason for lower reported Leak may be reporting error because of a possible difference in mask "resistance" (how much air goes through the mask vent holes as a function of mask pressure).

This is because the AutoSet also measures (in addition to the pressure at its output) the amount of air entering the blower, and any amount over whatever is estimated by the machine to be intentional vent is assumed to be Leak. If the actual mask resistance is lower than assumed by the machine then the actual amount of air going though the mask vent holes will be underestimated by the machine, resulting in overestimation of Leak.

For example, for times when the machine is delivering the same mask pressure, and if the Pilairo actually vents more air (has lower "resistance") than the Wisp, the machine will estimate higher Leak with the Pilairo, in comparison to its estimate of Leak with the Wisp.

The actual mask resistance for both masks may have been lower than assumed by the machine, in which case the actual Leak for both masks may be better (lower) than reported by the machine.

By the way, what settings are you using for Mask Type?

Take care,
---Vaughn
Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
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#6
With all the full face masks I have run into the manual has a graph of pressure vs LPM venting rate.
If the machine is working right it should be seeking the right pressure to keep the airway open in spite of whatever the mask venting rate is. I have a feeling that what is being logged by the S9 as a 'leak' is going to be any sudden pressure drop with a surge in flow rate. This would show up as a larger value in standard deviation for pressure variations from baseline.
A boost in cu. ft. per minute delivered by the CPAP would then compensate for the leak ie: bring the pressure back up to therapy levels. (...unless the leak is too large. At least that is how it SHOULD be doing things)
The fact that two different masks are coming up with different pressures for therapy levels does not sit well with me.
Any engineers out there to weigh in on this?

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#7

Hi Shastzi,

(01-20-2013, 09:14 PM)Shastzi Wrote: If the machine is working right it should be seeking the right pressure to keep the airway open in spite of whatever the mask venting rate is.

Agreed. I think it's probably delivering the needed pressure correctly, and the needed pressure is actually changing.

And I think the Pressure is probably being reported accurately.

(The accuracy of the reported Leak is a different matter, however, and depends on how closely the actual mask resistance matches the resistance assumed by the machine.)


Quote: I have a feeling that what is being logged by the S9 as a 'leak' is going to be any sudden pressure drop with a surge in flow rate.

Leak does not at all need to be sudden. For example, if the cap is left off an oxygen feed port on the mask, the leak will be always be there. And the machine will accurately determine how big the leak is by subtracting the calculated intentional vent airflow from the measured total airflow. Accurate, that is, as long as the resistance of the mask is what the machine assumes (based on Mask Type setting), and as long as the mask pressure is what the machine thinks it is. The mask pressure is the measured pressure at the machine, less the product of the measured airflow times the assumed hose resistance (based on Hose Type setting).


Quote:The fact that two different masks are coming up with different pressures for therapy levels does not sit well with me.

I think it is likely that the reported pressures are accurate, since the calculation of mask pressure is fairly straightforward, just measured pressure less the pressure dropped in the hose, and the pressure dropped in the hose is just the measured airflow times the resistance of the hose.

I think it likely that an unnoticed change in sleep posture or some other change may somehow be causing the change in needed pressure.

Take care,
--- Vaughn
Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
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#8
Thanks to all for the observations.

I should add that before using the Swift the first night (Friday) I changed the mask type setting in my S9 Autoset from "Nasal pillows" to "Nasal."

Regarding the observation that my leaks are too high, my (admittedly dim) understanding is that the S9 Autoset reports only total leaks, and therefore one should subtract "intentional" leaks to find the real leak figure. At my pressures, the "intentional" leaks should be about 37.5 L, therefore the leak figures I posted for the Wisp are pretty good, and even for the Pilairo, not outrageous. But I may have misunderstood what SleepyHead and the S9 Autoset are reporting for leaks.

My AHIs are below 2.0, so there is no need for me to be in a hurry to make changes. I am going to ride with 11-15 and my other current settings for a week or so and see what develops. I still think my leaks are less with the Wisp over the Pilairo, and the lower leak rate is causing the S9 Autoset to adjust the pressure more adequately, but we'll see what a few more days' data reveals.

Stay tuned! Smile
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#9
I don,t use SH
S9 display 95% percentile unintentional leak
what the S9 sleep report showing for last night leak

edit: last night data still shows on the sleep report as long as you took no nap during the day

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#10
Last night was my fifth night with the Wisp. I can now report that the leak and pressure data that I reported previously for the first two nights is continuing the same, that is, the S9 Autoset is going to higher pressures than it did with any previous mask, and the leak rate is less, although still a bit high, hovering around 30 L at 95%.

So now I am trying to figure out a way to cut down the leaks. I am going to adjust the headgear a bit starting tonight, but I suspect that I will get better results only when I go to a nasal mask liner. Unfortunately, I can't find any nasal liners that list the Wisp in their sizing data, since it is brand new on the market. I e-mailed RemZzzs just now, but I bet they respond that they have no idea which of their liners to use.

If anyone has used the RemZzzs liners (or any other liners) with a nasal mask, it might be helpful to compare the size. I am using the medium cushion with the Wisp and its dimensions are exactly two inches at its widest and two inches at its maximum height. The width of the flange that touches the face is about 3/8" all around. The shape is a rounded pinched triangle that is the same contour as other nasal masks that I have used. The big difference is that the size of the cushion is much smaller. In fact, I'll bet that if I ordered the smallest RemZzzs nasal liners that they have the liners would fit pretty well.

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