Low pressure

[silvercarper]

Lately I have been waking up in the early hours with my APAP just putting out 4cm pressure. Also I have been sleepy in the afternoon.
I have been to the hospital to get the lower limit increased but instead I get fobbed off so its still running 4-20.
I know how to increase the lower limit but out of courtesy I have not ever touched that menu but now I'm very tempted to go into it to tweak it.

[shuckie]

Hi silvercarper!

I'm probably being very naughty here, but I would encourage you to gradually increase your starting pressure if you're being fobbed off by your clinic.

I went with the initial configuration of my CPAP, however it didn't work for me and I read threads about other people resolving similar problems by increasing their starting pressure. I figured out how to access the Clinical menu as I couldn't alter the pressure settings from the Patient menu, and I gradually increased the pressure to a point where I felt more comfortable.

I would like to point out - especially for any newbies - that I have not increased my maximum pressure setting as it is probably dangerous for an unqualified person to do so, and a sleep technician increased it yesterday to compensate for the pressure drop caused by EPR being enabled. I'm asleep by the time my CPAP has ramped up to the new maximum pressure so it doesn't bother me. I also slept better last night than I have done for the previous several nights.

Please let us know what you decide to do (or not do!) and how you get on.


Kind regards

shuckie

[Tigers Fan]

The theory is ....

i slvrcarper

Did the nigt fishing rig work out OK?

There is a world of difference between an APAP and a CPAP. Theoretically, the APAP should give you the pressure you need when you need it - so if it's delivering 4 cm (lowest setting) it has decided you are sleeping like a baby and you don't need PAPing. Then, when you have an event, the machine's program cranks the pressure up to take care of it.

What I found was that the low pressure allowed apnoeas to happen and the subsequent high pressure was what woke me - the APAP gale roaring away. My solution was to increase the low set point and to reduce the high set point - to narrow the band in which the machine operated. A higher low pressure prevented most apnoeas while a lower high pressure reduced the gale effect (and was insufficient to deal with a 'deep' apnoea, which happened only very ocassionally).

I found my settings by switching to CPAP mode and finding the pressure at which (most) apnoeas stopped - the pressure at which I got good sleep. WHen I was satisfied with that, I switched back to APAP, setting the lower pressure (the top of the ramp) to that at which I had CPAPed and the high pressure to 5 cm above that. The extra 5 cm still gave me gle problems so I reduced gradually and came up with a magic number (for me) of 2 cm above base or set pressure. In other words, I pretty much reduced my APAP to a CPAP. I also minimised the A-Flex setting (EPR look alike) to minimise pressure fluctuations.

Another magic number is 4 - make setting changes not less than four days apart. Move in small steps. This way you get accustomed to change and can assess the effect. With large, frequent movements you'll not know whether you are coming or going. If your machine has a smart card and you can access your stats, the easier it is to assess results and chase your AHI ever downward.

My body and my sleep take precedence over courtesy to people too busy to follow up my therapy. At my last clinic appointmentI let my nurse wag his finger at me for altering my settings - he felt satisfied, I sleep well, everyone goes home happy.

Good hunting!

TF

[silvercarper]

I have hardly been able to fish at all lately because of more health problems.
As for the CPAP I was having a bit of a rant.
Next month I'm due to see the consultant and my card might be downloaded
if there is still a technician there to do it.
I will wait till then before I start altering the settings.

[James @ Intus]

In the end of the day, Auto-CPAP is a computer algorithm, based on models written after research on other people. Like all computer models, they won't be 100% correct all of the time. I remember vaguely the figure of >95% that they get it right. When they get it wrong, it's usually no big deal. It either means it's too low, and you may get an apnoea or it's too high and you may get some discomfort from extra air.

So usually, indeed some tweaking can improve matters. It's interesting that Respironics put their machines on a default range of 4-20 whilst DeVilbiss adopt a 5-15 range. The latter seems to yield fewer issues where people either feel the lower pressure seems too low (they want more air) or the higher pressure being too higher (causing leaks/noise etc.).

With the help of your clinicial, it should be no problem to adjust this. If you consider that on a fixed pressure CPAP, most people are at or around 11, 4 is actually quite low. And 20 quite high. When they look at the recorded data, in particular at the 95th percentile and 90th percentile pressure, I'm sure that they'll be able and willing to cooperate and narrow down the range somewhat if appropriate.

[Tigers Fan]

That reminds me ...

Hi James

At my last annual review they discovered I was using 17 cm (an extra half because I use a Whisperer and I guesstimate a half cm drop because of it) rather than the 10 cm they set my machine at two years ago. I've been on 16.5 / 17 for months and months.

Nurse Carol sought advice "because we only usually let CPAP go up to 16 cm" Male Nurse Pate came in and decided to do a waggy finger rather than address the issue. As I didn't want them disturbing my perfectly - well, largely - good sleep by messing me about with a new machine or whatever, I let the matter slide.

Finally, I've remembered to ask the question. What would be the problem with CPAPing above 16 cm on a machine operating betweem 4 and 20 cm?

For background, I get on better with a CPAP than my own APAP. I discovered this by sleeping better away from home with my Apex III than at home with my 'M' Series Auto. Tested over three trips away.

TF

[silvercarper]

It looks like the technician who deals with CPAP machines has been given other duties so I wonder what sort of back up I'm likely to have in the future.

[James @ Intus]

I don't know of any clinical reasons why >16 may be scary or otherwise something to steer clear of.

There are standards and guidelines about the technical capabilities of CPAP machines that are set out to prevent them to ever deliver over a certian amount of air:

http://www.artp.org.uk/en/sleep/sleep-standards/index.cfm

Any modern machine will have such safeguards in place.

My guess would be that they may think a pressure of over 16 may impact the important balance of O2 and CO2 to such an extent that they'd rather not go there unless the patient has had a full lung function review. But that's just a wild guess.

Quite a few people at the higher range of a CPAP's pressure tend to be more comofrtable with a BiPAP, given its explicitly lower exhalation pressure (EPAP vs IPAP). And BiPAP is a lot more expensive. That could be another reason they'd rather keep you closer to the average.

[Tigers Fan]

The stuff you know, James!!

Thanks for that - a very interesting site - except for one thing. The information is so deeply buried in explanation and reasoning and back-covering.

I shall do a bit of wading when the rain comes over. Fingers crossed it stays away till I've got a second coat finger dry.

Curiosity killed the cat and will be the undoing of me. I'm happy CPAPing as I am so why do I need to know what they 'usually do' at >16 cm? But I do!

TF

[James @ Intus]

Admit it, you just like that dumbfounded look on the tech's face when you outwit them again on your next visit

[Tigers Fan]

I would love to!

To change the look of bewilderment to one of comfort in their knowledge would be wonderful! They know what they need to know to get a newbie out of the door and they give me no clue of greater knowledge after that!

If only Nusre Ali wasn't so busy being a Mum!

TF