Hypoventillation / Low Minute Ventillation - AutoSV

I have complex apnea and finally got tired of my AutoSV waking me up in the middle of the night with a low pressure support warning (the PRS1 AutoSV has an alarm which cannot be disabled via configuration), so I did a bit of surgery and disabled the buzzer and it is now completely silent.

My first night in this state actually transpired without an alarm, but after my second and third nights I woke up to see a red light on the machine indicating that it had alarmed during the night. This is probably the first three-night series in the last two years that I've managed to sleep without getting out of bed. So, overall I'm happy with the change.

However, I did pull up the data in SleepyHead to see what was happening. My third night had the most interesting results. There were a few periods where the machine was ramping the pressure support up until the machine hit its max 25cm output. One of them lasted about 15min. During that period of time the EPAP was 8cm and the IPAP was 25cm, and my breathing was obviously shallow just looking at the flow chart. Inspiration/expiration time was normal, tidal volume was about half normal, and my minute ventillation was less than half normal, at maybe 3.75L/min or so for that whole period of time (8-9 seem to be more typical for me at rest).

I don't have any way of monitoring my SpO2 at night, but obviously I'd be curious as to what it was during those periods.

I guess my question is whether this is something I should be concerned with. I couldn't find a lot of information online about hypoventillation. As far as I can tell the prolonged low-volume period did not end with my waking up or anything like that - it looks like my breathing just picked up again. My AHIs seem to be around 1.75 - all hypopnea with maybe 1-2 snore detections in a typical night. The 8cm of EPAP seems to address all my obstructive issues completely.

Thoughts? I know there are a few with complex apnea around here.

rich0 wrote:I don't have any way of monitoring my SpO2 at night, but obviously I'd be curious as to what it was during those periods.

you can pick up an excellent wrist mounted oximeter for under 100$ from aliexpress.com... the cms50i, sleepyhead imports it's data directly.

if you're concerned, it might be worth the peace of mind, or, it might let you know you need to pick up an oxygen concentrator.

Have you been diagnosed with hypoventilation? Are you very overweight?

Hypoventilation takes a different kind of machine. I don't thing the ASV machines treat hypoventilation. That requires an AVAPS or iVAPS machine. There are also some more complicated machines, some called "ventilators" that have more complex therapy settings.

BTW, I'm not very familiar with hypoventilation, but I do know it's considerably different from the more common OSA/CSA conditions, especially in how it's treated.

There were earlier threads that addressed this issue. Perhaps they contains information that will be helpful.

Low-pressure-support-alarm-in-BIPAP-AUTO-SV

ASV-low-pressure-support-error-and-alarm

From the dates, the earlier one might be referring to a 950 ASV machine rather than the 960 which is the current model.

Edit: In the User manual for the 950 ASV machine is the following:

This could be caused by an excessive leak or blockage or a device malfunction. Press the Alarm Silence/Indicator button to silence the alarm. Remove your mask. Check for the following: dirty inlet filters, blocked air intake, excessive leak in the patient circuit. If the alarm continues, contact your home care provider.

This a warning from an ASV diagnostic procedure that I got online.

archangle wrote:Have you been diagnosed with hypoventilation? Are you very overweight?

I have not been, and I'm overweight, but not excessively so, and I sleep on my side.

I don't think it is a machine issue either, as the machine does reach 25cm which is its max pressure. If it were really a leak problem I'd think that it wouldn't be able to achieve the pressure setpoint. I suspect that the alarm just means that the minute vent is low even when the machine is administering max pressure support.

I'm sleeping fairly well so right now I'm inclined to ignore it. But who knows, maybe I'll end up on a ventillator someday.