ResMed S9 VPAP Auto - unexpected shutoff while sleeping

[McSleepy]

A few days ago, in the morning, my machine suddenly shut off while I was sleeping and I woke up immediately and turned it back on and went back to sleep. This had never happened before - not with the S9 nor with the S8 before that, nor with any of the other machines I've had. They have all been set to auto start/stop, so my first thought was that this mechanism somehow kicked in. Here is the graph of that event:
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S9 shutoff 1.png (94.33 KiB) Viewed 393 times

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The data shows a significant leak developing right before, so this is an option worth pursuing. The last recorded leak flow was 84 L/min.

I tried a test where I'd plug the outlet and increase the leak until it stopped in order to measure the flow. Unfortunately, the S9 does not record the data with a sustained flow level and a great leak, so I tried with breathing normally and slowly removing the mask until it stopped. Once again, the data stops well before the shutoff occurs, but it was able to record a leak level of 97.2 L/min:
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S9 shutoff 2.png (75.08 KiB) Viewed 393 times

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I use an elaborate head-gear that keeps the mask tightly to my face, but it is hard to contain 22 cm H2O, so I can't quite exclude that explanation (especially with the rise of levels leading up to the event), but I can't be sure. I've read here that people have had their machines shut off spontaneously and it was related to a malfunction, so I'd like to consider that option, too. Obviously, since this had never occurred before, it is a very low-probability phenomenon and I can't do experiments of the "try this and see if it happens again" kind. So I hope to collect some personal experience: has anyone (preferably with the same machine) had this happen to them, and if so - under what circumstances?

McSleepy

[Posey]

I had a similar experience- twice -and for me it was high leak rate that shut off the unit. I verified it on Sleepyhead. I changed masks and haven't had any further problems. If your mask seems pretty good, be sure the hose isn't leaking from a tear or at the connections. Good luck.

[McSleepy]

I had a similar experience- twice -and for me it was high leak rate that shut off the unit. I verified it on Sleepyhead. I changed masks and haven't had any further problems. If your mask seems pretty good, be sure the hose isn't leaking from a tear or at the connections. Good luck.

Thanks! I'm leaning towards that explanation, too. The machine has over 11K hours, but it should still be good. There is a small leak at the swivel connector of the mask's hose as there is some off-axis force applied, but it is negligible by comparison to the mask exhaust. The mask is heavily modified or it wouldn't stand a chance of staying on my face (I sleep face-down). I must have leaned and dislodged the mask pillows for a moment. I'll only worry about it if it happens again. I can always disable auto-start/stop; it's just a convenience for starting the machine.

McSleepy