[Equipment] A new ResMed AirSense 10 fails to do Smart Stop when at higher altitude.

[mountaincat]

I have my Air Sense 10 set to provide Smart Start and Smart Stop. It consistently starts on its own. Although at lower altitude it stops within four seconds of mask removal (as my S9 did), at higher altitudes (Flagstaff, Santa Fe), it never stops even if I let it run for an hour.  Is this a known issue?

[Sleeprider]

I have not personally had problems at altitude up to 7000 feet (Steamboat Springs and Santa Fe). There seems to be variation in these units and the masks being used. We havel Colorado members that have not reported an issue.

[mountaincat]

Thank you, Sleeprider.  The actual data points I have for it not smart stopping are in the 7000 foot ballpark (at home at 7500 and on the train passing through Arizona more like 6800). Previously during a couple weeks in California the smart stop  worked everywhere.  I gather from your reply that it is not a known issue that has to be lived with. I can experiment with different masks to see whether that has affected its reading. 
I like the convenience of the smart stop but the more serious concern is that the device might not be reading the change in pressure or flow correctly if it doesn’t know that the mask has been removed.  It is a new device so I want to exchange it if might have a hardware or software defect, but not without responsibly checking it out myself.

[DigitalMan43]

I live at 7000 feet in Colorado and have never had a problem with auto start or stop on my previous Airsense 10 or my current Airsense 11. I've used the AS10 up to around 10,000 feet in the mountains without problems. Even though I had no problems, I learned they're not rated for that high. I don't recall the exact numbers, but do remember that the AS11 was rated higher than the AS10, so that's one reason I got it over another AS10.

[mlmollenkamp]

Since yours is a new machine this may not apply.  
My AirSense 10s auto start/stop stopped working.  It would start on its own and not turn off.  This started rather suddenly.   The machine is 6 years old with 16K hours on it.  It took some doing but I  convinced Medicare to replace it. The new machine is another AirSense 10, basically identical but with a modem that works and newer firmware.  
It was obvious after the first night that the new machine was working better. Its almost certain that something happened to the airflow sensor on the old machine.  The new one consistently registers higher tidal volume than the old, about 25% averaged over the night.  Most of the time the old one would ramp up pressure to the maximum and rarely come down.  The new one is working much better, it lives in the middle of the range most of the time, moving up and down as you would expect.  It clearly responds to CA's with increased pressure, and ramps down the pressure when everything is stable.  
Its telling that the average tidal volume on the new machine on average reads about 25% higher, i.e. the old one saw lower airflow than the new one.  Hence auto start didn't work, and the ASV ran the pressure higher than necessary..  I have complex apnea so my centrals were through the roof.  With the new machine I have very few of either and feel a lot better.  

If auto start stops working on a Resmed AirSense machine it's probably not just that feature that's affected, the therapy probably is as well.  The auto start feature relies on the airflow sensor to know when you put on or take off the mask so auto start issues are most likely to be related to airflow sensing.

[mountaincat]

Digitalman43, thank you.  It sounds as if it should work at 7500 feet if it has worked regularly for you at 7000 feet. But thanks for mentioning about the rating.  I should try to find out what elevation that mentions.

[mountaincat]

Thank you, mlmellenkamp.  My smart start has continued to work, but I am concerned that the failure to smart stop at least home at 7500 feet indicates a problem with the air flow sensor which could be affecting therapy in other ways. Your info and comments will help me explain why I want to replace the unit under the warranty.