In search of leaks

[Warning: may be TL;DR for many]

Note: Many of us have chased leaks at some time. These are some notes from my ongoing quest to understand them better.

I have been seeing strange consistent 7 cmH2O leaks for a while. I’ve chased it more from an academic perspective than concern, as PaleRider has said in another thread it is well within the acceptable leak range.

Quick background. I have two CPAPs, one in the bedroom and one in the media room (where I tend to sleep when the boss is sound asleep already or I just fall asleep watching real football). Both are Resmed AirCurve 10 VAuto bilevels with similar hours. When I use the one in the bedroom it shows in OSCAR a 95% leak rate of 0.0, but the one in the media room shows a 95% leak rate of 7.0. As I said, I am not concerned about it, but I’m curious why.

So, what is going on? Putting on my best Sherlock Holmes outfit, the game is afoot! One thing I did learn early with the VAuto is when pressure is on and you go to the “Sleep Report” screen, there is at at the top of the screen something that says “Sleep Report 1/3”. What I realized is if I turn the main button one click or more you can get to the other screens there. On screen 2/3 you can see a realtime leak rate, along with other stats.

Off to test by swapping some pieces between the two machines…

• Mask swap = same result

• Hose swap = same result

• Water chamber swap = same result

Bugger it all. So nothing is leaking from the easily replaceable pieces. Now what? Either live with the 7 cmH2O difference between the two machines or continue debugging.

Debugging it is…

The only parts of the leaking CPAP that (in theory of course) could possibly allow leaks are one of the three components I already tested for leaks. It could possibly have an internal leak, but that seemed unlikely, so what else could it be?

The remaining logical place for leaks is from the humidifier chamber air outlets. There are no obvious cracks or separations, so I tried different ways to insert the water chamber. Lo and behold! When I used a bit more force to insert the chamber there were no more unexplained leaks. Voila!

Now, how to deal with it. I found on our sponsors site cpap.com a replacement humidifier chamber air outlet for around $10 USD. I will replace the air outlet when I place my next order from cpap.com.

The moral of this story is that sometimes CPAP leaks are real leaks. Remember to check the bloody obvious before getting too into the weeds of changing settings, mask, hose, chambers, etc.

Le Fin.

Unless you uses both machines at exactly the same time, in exactly the same place, the comparison is useless.

LSAT wrote: ↑

Sat Dec 10, 2022 12:46 pm

Unless you uses both machines at exactly the same time, in exactly the same place, the comparison is useless.

Completely agree. Not at the same exact instance in time of course, but I did switch between them within a few seconds. During the testing when I switched the outlet port from the 0 cmH2O leak unit to the 7 cmH2O leak unit and vice-versa, the leaking unit leak went to 0 cmH2O and the non-leak unit showed a 7 cmH2O leak. Given the only variable (other than the physical CPAP machine) that changed was the outlet port, it appears to logically point to it being the causation. I’ll know for certain when I get a new outlet port.

I should have put that in the original post. Thanks for the suggestion.

Argh! Spoke too soon. The backup machine continues to have baseline leaks of 7.0 during sleep even though it records 0.0 during brief testing. There must be something leaking somewhere as all external connections (mask, hose, water chamber) when placed in my primary machine records leaks of 0.0. I've tried using tissue paper to find any external leaks and nothing so far.

Back to the drawing board, but I may have to send it out to acbio for a checkup. I would not normally be bothered by it, but my AHI is ~4x (2 vs 0.5) what it is on the primary machine and sleep is not as restful. It seems worthwhile checking it out as it only has around 3600 hours on it.

If there are any other thoughts it would be most helpful.

Are both units set to the same mask setting?

lazarus wrote: ↑

Mon Dec 12, 2022 10:36 am

Are both units set to the same mask setting?

Both are identically set up, at least as far as every parameter available in clinician mode. I've even tested multiple nights on each using the same external connections (mask, hose, water chamber) and the 6-7 cmH2O leaks remain on the backup machine while the primary is 0 cmH2O leaks.

All I can think of is there is something leaking inside the unit, but before I take it apart or send for service I am wondering if anyone has other suggestions.

So they are both set to "Pillows"? On my machine it is in "My Options," not the Clinician settings.

lazarus wrote: ↑

Mon Dec 12, 2022 11:35 am

So they are both set to "Pillows"? On my machine it is in "My Options," not the Clinician settings.

It's in both places on the VAuto, though I have not checked on a Resmed non-VAuto. If you change it in "My Options", it changes it in the Clinician settings, and vice-versa.

Jlfinkels wrote: ↑

Sun Dec 11, 2022 9:03 am

There must be something leaking somewhere

No, there doesn't *have* to be a leak somewhere, there could be something wrong with the sensors.

Even if there was a leak of approximately 7??? (cm of H20, or LPM), that is nothing, and the device would easily adjust for that. There would be no net change in pressure.

Have you compared the Mask Pressure to Pressure?

You also not comparing AHI on one machine to AHI on the other. You are comparing the spare machine and sleep environment (media room) to your nightly machine and bedroom. What are you sleeping on in the media room a couch? A four fold increase in AHI is better explained by the change in sleeping arrangement than a change in leak amount. Adding to the list of missing information; how statistically significant is your comparison of the "leaky* machine to the bedroom machine?

Some things to try:

• Actually use your "leaky" machine in the bedroom for a month, then compare AHI.
• Post some graphs, comparing the "leaky machine", 2 AHI nights to the non-leaky 0.5 AHI nights.
• Post the OSCAR statistics of the one machine to the other, this way we can actually determine the therapy differences and statistical significance. Perhaps see other potential oversights you've made.
• Post some comparison graphs of Mask Pressure vs Pressure

Jlfinkels wrote: ↑

Mon Dec 12, 2022 11:40 am

lazarus wrote: ↑

Mon Dec 12, 2022 11:35 am

So they are both set to "Pillows"? On my machine it is in "My Options," not the Clinician settings.

It's in both places on the VAuto, though I have not checked on a Resmed non-VAuto. If you change it in "My Options", it changes it in the Clinician settings, and vice-versa.

The availability of the Mask Settings in My Options is not related to AirSense vs AirCurve, it's dependent on the Essentials (On/Plus) setting.

Dog Slobber wrote: ↑

Mon Dec 12, 2022 11:52 am

Have you compared the Mask Pressure to Pressure?

Brilliant. I never thought of that. I’ve attached recent graphs of pressure and mask pressure. Not quite sure what I should be looking at here..

Dog Slobber wrote: ↑

Mon Dec 12, 2022 11:52 am

You also not comparing AHI on one machine to AHI on the other. You are comparing the spare machine and sleep environment (media room) to your nightly machine and bedroom. What are you sleeping on in the media room a couch? A four fold increase in AHI is better explained by the change in sleeping arrangement than a change in leak amount. Adding to the list of missing information; how statistically significant is your comparison of the "leaky* machine to the bedroom machine?

I have done this before and things were consistent on the DUT (Device Under Test) regardless of which room was slept in that night.

Not sure what you mean about a statistically significance of the two machine.

Dog Slobber wrote: ↑

Mon Dec 12, 2022 11:52 am

Some things to try:

• Actually use your "leaky" machine in the bedroom for a month, then compare AHI.
• Post some graphs, comparing the "leaky machine", 2 AHI nights to the non-leaky 0.5 AHI nights.
• Post the OSCAR statistics of the one machine to the other, this way we can actually determine the therapy differences and statistical significance. Perhaps see other potential oversights you've made.
• Post some comparison graphs of Mask Pressure vs Pressure

Roger dodger. I’ll collect more data over the next few weeks and post some results.

Thanks very much for the suggestions!