Sierra

Yes, flow limitation and obstructive events are related. Flow limitation often precedes an obstructive event. I think your basic problem in getting a prescription for a BiLevel machine is that your current machine is getting your AHI below the standard 5 level which is considered acceptable treatment. It is struggling a lot to do it, and frequently is hitting the 20 cm limit of the APAP, but the average AHI is still reasonable from a medical treatment perspective. So, the AHI is the weak point of your argument for a BiLevel machine. Your strong points is the duration of time that the machine is at 20 cm of pressure. I would expect that is not all that comfortable and may impact your sleep, and she should be told that (if it is true). The big advantage of the BiLevel for you is not the maximum pressure increase, it is the Pressure Support of up to 10 cm that would be of value to you. She should know that Pressure Support is what is needed in the case of flow limitation issue. Again you would need to convince her that flow limitations are a problem affecting your sleep, and need to be reduced independently from reducing the frequency of obstructive events. It is a bit of speculation on my part, but I would expect your overall pressures would go down if you had more than 3 cm of pressure support. What you really need is breathing support from a bigger differential between IPAP and EPAP. This addresses flow limitation on both inhale and exhale.

The other evidence you could give here is a zoomed in shot of your flow rate during these times of flow limitation. Not sure what yours looks like, but my wife has higher flow limitation than I do, and here is an example when FL gets up to 0.5 or so. You can see that the tops (peak inhale flow) of the breaths are flat topped and irregular. If yours are similar, that would be something you could take an image of an show her.

From the look of the flow chart it would appear my wife suffers more from flow limitation on inhale (up direction) compared to exhale.

Here are your options to control pressure in the VAuto mode, and a description how it works.

To make the machine as close as possible to what you had I would set the Max IPAP at 20 cm, Min EPAP at 5 cm, and the Pressure Support at 3 cm. This is assuming your EPR was set at 3 cm. And now with the AirCurve machine this Pressure Support can be set higher than 3 cm and as high as 10 cm. And of course the IPAP can be set higher with a max of 25 cm.

I have a pdf copy of the Clinical Manual for this machine, but no good way to get it to you, unless you are willing to post an email, and then I could send it to you.

I can't reply for some reason to your post about changing your device in OSCAR. Perhaps because you did not put anything other than the title of the post? Not sure. In any case I think all you need to do to change your device in OSCAR is just download the data from the new device into OSCAR, using your same ID as with the old machine from the new SD card. If OSCAR is like SleepyHead it will recognize the new device and just add it on to your existing data. Under the Statistics Tab there should be the new machine listed and the date when you first used it. This way you will be able to compare your data from the old machine to the new machine.

What do you mean by "I want to increase the amount that I exhale"? Do you want to reduce the exhale pressure or EPAP by more than the 3 cm that the A10 was capable of with EPR?

The best thing you could do is download OSCAR to view your results in detail. If you have your SD card from the A10 machine, download the data from it first. Then download the data from your A11 machine. OSCAR is smart enough to store your old data, and then start displaying the data from your new machine. This will allow you to compare what was happening with the old machine compared to the new. You will need a PC or Mac and a SD card reader to do this. And if you have a full SD card from your A10 it will take some time for it to download all the data, as I believe it stores up to a year on the standard card. And, if you do not have the old card, just post your current Daily screen here. Press F12 on a PC and then watch where it saves the file. Use File Explorer to find the screenshot and then left click on it and drag it into a full width window of a post.

Yes, I am familiar with Alstom. One power plant in our company had GEC turbines and Combustion Engineering boilers. Alstom ended up buying both of these companies so we depended on them for service.

Interesting. I spent about 35 years in electric power generation, starting with Ontario Hydro, and later in Alberta. My experience is primarily in thermal generation, and in the later years also some smaller hydro and run of river hydro.

Keep in mind that I am not a medical professional. Like you I am a retired engineer with sleep apnea that is now pushing 73! Your summary is basically correct. My theory is that you need breathing assistance more than just higher pressure. Breathing assistance is gained with more pressure differential between IPAP and EPAP. My hope would be that with more differential, your IPAP would not need to be so high. The reason is that you don't seem to be having a high obstructive apnea frequency, and it is flow limitation that is causing your CPAP to raise pressure, when what you really need is more differential.

Engineers like graphs. This section of the VAuto Clinical Manual may help in understanding how they work.

It can be confusing as for some reason ResMed and others changed the vocabulary from the APAP machine to the BiPAP. Let me give a go at trying to explain each:

APAP - "Pressure" is assumed to be the IPAP (red on OSCAR). You set this pressure with a minimum and maximum. In your example 6 cm minimum, and 15 cm maximum. The machine will automatically increase and decrease the pressure (IPAP) within that range during the night. Independent from this you can set a pressure reduction on exhale EPR of up to 3 cm. So for example if the machine is asking for 10 cm of inhale pressure, and you have EPR set at 3 cm, it will give you 10 cm on inhale and 7 cm on exhale. On Oscar this is the red and green trace respectively.

BiPAP - For strange reasons that I don't understand they have assumed the convention that "Pressure" is now the exhale pressure or EPAP. This is likely for marketing and hype purposes. You can set a minimum and maximum range of that EPAP pressure just like in an APAP machine which it will adjust automatically during the night. Again separate from this you can set a "Support Pressure". This is like the EPR on an APAP, but is an increase instead of a decrease. This pressure support can be as much as 10 cm. If you have it set at 10 cm, and the machine wants an EPAP of say 8 cm, You will get 8 cm on exhale, and 18 cm on inhale.

The key difference is than on an APAP the maximum differential between EPAP and IPAP is 3 cm and is set with EPR. In a BiPAP the maximum differential is 10 CM and is set with the Pressure Support. Both EPR and Pressure Support create a differential between inhale and exhale which assists in breathing, but the Pressure Support on a BiPAP provides much more.

To get considered for a BiPAP or BiLevel machine like the ResMed AirCurve VAuto you should show your doctor the graphs where pressure is hitting the maximum level of 20 cm of pressure, with flow limitations still spiking high. That is a strong indication that a PAP device with a maximum pressure of 20 is not enough for you.

And I am not sure that this pressure maximum is the the most important issue. It could also be that the 3 cm of pressure relief is not enough. You may need more than a 3 cm difference in pressure to adequately assist breathing and reduce flow limitations. The VAuto can go up to 10 cm of pressure support (differential between IPAP and EPAP). It is possible with a higher pressure support your maximum IPAP pressure could be reduced to a level lower than 20 cm. Just for example you may get away with a maximum pressure of 15 cm, but with a 10 cm pressure support. Then the machine pressure will alternate between 15 cm on inhale and 5 cm on exhale. This could be much more effective and more comfortable than what you are getting now, which is 20 cm on inhale and 17 cm on exhale.

Here is a short article BiLevel Positive Airway Pressure to look at.

In Canada the AirCurve 10 VAuto seels for about $2300 compared to the A10 or A10 AutoSet at $1300.