A New Question on Pressure

[mars]

Hi

I have just been reading the thread on A Question of Pressure, and as I do not want to hijack that thread I am asking these questions separately, and I hope the wise will respond to this.

My Apap pressure is set at 8 - 12,5, with a Maximum Pressure for Command on Apnea of 11.5. Now on my Waveform Report I can start out at steady 8, and then the pressure will go up and down as time progresses.

However, I often get flat lines for between 30-60 minutes at a pressure of 9, or 10, and even up to 12. There is usually an event at the start of these straight lines, but not during them.

So what is happening during these 30 to 60 minutes of constant pressure. There have been occasional AH events during this time, but not often.

I have another question which you may be able to answer.

Can a hypopnea be an apnea which was forestalled by the machine, or is it always a discrete event in itself.

I recently had a night when the pressure got no higher than 9, with an AHi of 0.9. Mainly on 8 all night, with a couple of flat lines at 9. I find this peculiar, and wonder if it means anything.

cheers

Mars

[dsm]

A quick reply to the can a hypop be a forestalled apnea (will need to think about the other points).

But I believe yes. As pressure is raised, the airway is usually held more firmly open. Part of the
story is just how serious an OSA event is that is looming. i.e. what is causing it.

But as the machine responds to precursor signals (snores, hypops, flow lims (& flattening)) it can pre-empt and reduce the severity of what might have been a no-flow apnea. So a no-flow apnea can be turned into a hypopnea (in advance) if the machine was raising pressure in response to pre-cursor signals.

Cheers

DSM

PS the above reply recognizes you have a Sandman machine - the answer may have been slightly different (conditional) had you had an S8.

[ozij]

So what is happening during these 30 to 60 minutes of constant pressure?

You breathing is smooth, you're (I assume) sleeping well, and there's no need to raise the pressure.

There have been occasional AH events during this time, but not often

If the Sandman picks up the sound of your heartbeat while you have an apnea it will not respond to the apnrea by raising the pressure.
Similarly, if the Sandman identifies a hypopnea without indications of flow limitations, it will nor raise pressure in response that apnea.

The cardiogenic (=caused by the heartbeat) oscillation on the airway is an indication that the airway is open, i.e. a central apnea.

The above apneas will be reported as "apnea /cnt" and the hypopneas as "hypopnea /cnt".

Both kinds of /cnt events may be the result of your turning over, sighing, etc.

O.