[Treatment] PAC (Pressure Assist Control) Mode

[airbusA346]

Yours is an interesting and unique case.  Thanks for keeping us posted here at its a new approach.  The more we know about what leads to this recommedation, the more helpful this will be to someone that may have a similar problem in the future.  Thanks for sharing.

I'm not sure I like being such a unique case.  This all started in Oct 2014 when I was diagnosed with mild OSA and my local sleep clinic initially refused to treat.  Eventually they gave me an APAP and after several years of trying to get them to do something because treatment wasn't working, I transferred to the Royal Brompton in London in November 2017 where they diagnosed nocturnal hypoventilation and I was given my current machine in March 2018.  And I am at the current point where it has been decided my current machine isn't treating me successfully.

And to date I or the hospital don't know what the underlying cause is... and it wouldn't surprise me if I don't find out.

[airbusA346]

Bit of an update, I've now been switched to the Resmed Stellar 150. PAC Mode 32/12.

[Sleeprider]

Airbus, your therapy is outside the realm of most of our experience here. Does it give you relief from symptoms? That is a lot of pressure support (20 cm).

[airbusA346]

Airbus, your therapy is outside the realm of most of our experience here.  Does it give you relief from symptoms?  That is a lot of pressure support (20 cm).

Not yet... I've only been using it since Tuesday, so not sure how long I'm supposed to give it, before changes to settings etc maybe needed.

[Matt00926]

Pressure assist-control can be helpful in cases where an inhalation would otherwise be terminated prematurely. In PAC mode you set an inspiratory time and the inhalation will last for that programmed time on every single breath before the exhalation phase of a breath occurs. Maintaining an inhalation for the proper amount of time helps make sure their is enough time for gas exchange in the alveoli and helps make for more adequate and even tidal volumes.

My guess is the source of your nocturnal hypoventilation is the scoliosis. Scoliosis can cause a restrictive defect even when the lungs themselves are healthy. If severe enough it interferes with the ability for your lungs to fully expand because of the deformed chest wall.

What is your Ti min and Rise time set to when you used ST mode? From your other thread it looks like you are way overventilated sometimes hitting tidal volumes of 1000ml and minute volumes that are way higher than normal. It doesn't seem you sync well with the machine as set. Most important is optimizing the additional settings before going too crazy with IPAP and EPAP.

A pressure support of 20 is high but it isn't unheard of in actual studies dealing with respiratory insufficiency. Still 32 and 12 sounds abnormal and I'm surprised a mask can even stay on your face and seal well.

[SarcasticDave94]

Hope all is well airbusA346. My unique combo of COPD and Complex Apnea has me involved in a machine change with therapy needs more than what I believe my ASV is suited for. I feel I need time controls I can adjust like on an ST-A. It sounds like the Lumis you had is the AirCurve 10 Series ST-A with iVAPS mode I'm trying to get now. If it were up to my Apria DME medical equipment office, due to my COPD diagnosis, they'd issue a Respironics Trilogy, which is a ventilator.

I'm studying things involving my COPD derived therapy requirements, and I'd be happy to pass info learned that might help. I had researched some on the ResMed Stellar and Astral series devices. Yep these are extra rare here on Apnea Board.

I'm not sure I've got anything useful to help right now to pass on. As is, if I do pass anything that may help, it's an emphasis on machines not the medical reasons for the machines. Obviously, I'll defer to your doctor's medical directions. Don't let that stop you from asking. If it's a question I can answer, I would be happy to help.

It's possible it will take a little time to get comfortable with your Stellar therapy. But at the right time, I'd guess there will need to be setting edits to make it your best therapy. Maybe create a diary of the things you'd like therapy to improve on: this feeling of whatever that you'd like to note is good, bad, otherwise. At least you'd have notes to inform the doc.

[airbusA346]

What is your Ti min and Rise time set to when you used ST mode?

When I was on ST with a pressure of 26/9 with RR of 18 my Ti Min was 1.0 and Max was 1.8. I can't find rise time in ResScan.

Hope all is well airbusA346.

Not long after I got home with the Stellar, I decided to use my oximeter to see if things had improved. Unfortunately the results weren't good and I was still getting desaturations. After a short wait I was sent a remote access module for the Stellar, so the data could be sent to the hospital for them to monitor. They also sent me a oximeter module that plugs into the back of the Stellar. They also had Resmed send me a F20 AirTouch mask to try, so they could check it wasn't the FitLife causing the issues.

Apparently the F20 worked better with regards to ventilation and saturation, but like all other full face masks it causes damage to my nose and it also leaks like mad. So I've had to tell the hospital, even though the F20 gives better numbers, it isn't the solution and has to be discounted and the FitLife is the only mask to work with.

As of last night I am waiting for further discussions to take place between the consultant and chief physiologist on what happens now, because I am still getting desaturations into the 40, 50, 60, 70% range throughout the night, every night.

Oh and I get bloating every night. Quite often too my stomach/abdomen ends up rock hard.

[SarcasticDave94]

No fun being between rocks and hard places. Sincerely hope your team gets something figured out.

[Matt00926]

What is your Ti min and Rise time set to when you used ST mode?

When I was on ST with a pressure of 26/9 with RR of 18 my Ti Min was 1.0 and Max was 1.8.  I can't find rise time in ResScan.

Hope all is well airbusA346.

Not long after I got home with the Stellar, I decided to use my oximeter to see if things had improved.  Unfortunately the results weren't good and I was still getting desaturations.  After a short wait I was sent a remote access module for the Stellar, so the data could be sent to the hospital for them to monitor.  They also sent me a oximeter module that plugs into the back of the Stellar.  They also had Resmed send me a F20 AirTouch mask to try, so they could check it wasn't the FitLife causing the issues.

Apparently the F20 worked better with regards to ventilation and saturation, but like all other full face masks it causes damage to my nose and it also leaks like mad.  So I've had to tell the hospital, even though the F20 gives better numbers, it isn't the solution and has to be discounted and the FitLife is the only mask to work with.

As of last night I am waiting for further discussions to take place between the consultant and chief physiologist on what happens now, because I am still getting desaturations into the 40, 50, 60, 70% range throughout the night, every night.

Oh and I get bloating every night.  Quite often too my stomach/abdomen ends up rock hard.

Did they tell you why your EPAP is so high? Unless you have documented obstructive apneas it should be a lot lower. A high EPAP is hard to exhale against and could be increasing your work of breathing. It also requires your IPAP to increase as well in order to maintain the same level of pressure support. This is uncomfortable and clearly 32/12 means your mask is going to leak and you're getting a ton of air pushed into your airways. 

If you don't mind experimenting for a night, I could suggest some settings in the PAC mode to try for a night of sleep. I would then like to see your sleepyhead/oscar data and tell you some changes to make. 

I think as set your backup rate is probably way too high, hence why you're only spontaneously triggering like 2% of the breaths. This is uncomfortable and most likely causes asynchrony. If you have a bunch of breaths that get cut off the therapy isn't able to do what it needs to do. Sometimes they set the rate just above your natural rate to "capture" your breathing and control the ventilation more, but whatever they are doing is clearly not working well for you.

Rise time value you can see in the clinical menu on the machine itself, to see what it's set to. 

Anywho let me know if you want to trial some settings, I am very familiar with the bi-level modes of ventilation after having to teach myself everything since my local physicians are clueless when it comes to it. 

It would be helpful if you can list out all of your current settings in the clinical menu so we can get a better idea. 





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[GuernseyBunker]

Very interesting to read the prior posts about PAC

Although unrelated to the OP therapy requirements, as a Lumis 150 VPAP ST-A owner I have been testing a variety of therapy modes in order to optimise SpO2 concentrations (Nonin 2500A) with and without supplementary O2 should the (Covid-19) need for additional support arise.

What I have discovered is that PAC is the most effective and comfortable means of obtaining reliable and consistent +97% SpO2 based on the following personal settings and ambient air:

Therapy mode: PAC
IPAP: 20
EPAP: 5
Backup Rate: 10
Ti: 2.5s
Rise Time: 900ms
Trigger: Very High
Mask: Full Face

I am not suggesting a therapeutic modality - just posting personal observations based on having experimented with VAP on a Lumis 150 ST-A + Nonin 2500A Pulse Oximeter for SpO2 verification purposes.

What risks are associated with utilising PAC in this way for the purposes of short-term NIV?