Why Won't a Pressure Range of 4-20 on APAP Be Effective?

[upsman]

I regularly see people post things like "Don't worry about setting your pressure. The machine is automatic and will adjust as needed." 

I would like to explain to them that this isn't technically accurate. My understanding is that this pressure range is generally the default setting and considered "wide open" and not very effective for most patients. I've read that a minimum pressure of at least 6 cm is found to be most comfortable for most adults. How can I explain to these people that there needs to be a set range of pressure based on the degree of treatment needed? 

My basic understanding is that if a patient needs 7 cm to treat their apnea, then starting at 4 would require too much time to reach the effective pressure. There seems like there is more to this than that. I also understand that the max pressure is not as important unless the machine is consistently pushing it at or near that pressure. 

Any advice or guidance here would be appreciated.

[SarcasticDave94]

Default is the factory minimum and maximum settings. Maybe this is an interesting comparison, look at your vehicle. There's several brands, Goodyear, Bridgestone, Cooper, Michelin, etc. that your car could have installed.

My 2005 Dodge Caravan takes 225/70-15 in whatever PSI, say 35 just for a number. The sidewall of Goodyear all season something or other may say Max PSI 40. That's not saying I need to put 40 in the tires for mine. Suppose that there's a minimum PSI of 15, but my normal everyday on the road requirement then 15 PSI isn't right for my circumstance. 15 may be just fine for rock crawling or sand, but not around town pavement use.

Suppose this Goodyear tire has that range of pressure 15-40, somewhere in that area is my right pressure but it doesn't need to be 15 or 40 because that tire factory listed the default PSI range.

[NelsonM]

So I'm new to this and I'm sure the experts will come along.. But I started with an Resmed 10 Autoset about six weeks ago with the doctor's prescription of default 4-20 pressures and have been slowly adjusting based on advice in this forum. The machine has decided my median pressure is about 11.

I raised the minimum pressure to 7. The theory on this is that the EPR that lowers pressure by 3 when you exhale still has a minimum value of 4. So you have your choice of 4 to 4 at default settings, or 7 to 4 if you raise the minimum pressure to 7. The default 4 to 4 is basically just constant pressure, no EPR at all, so the 7 to 4 feels more comfortable. I also noticed with OSCAR that the machine pretty much never ran at just 4 for me, it was ramping up to 7+ anyway on its own all night as soon as it detected I fell asleep, so why not start there?

I've also lowered the maximum pressure gradually and am now at 15. Mostly based on the observation that the machine very, very rarely has gone over about 14 on its own for me. (Again, using OSCAR to see.) And the few times it did go over 15 were annoying enough to wake me up. In particular 18+ causes very large leaks with my mask and while I could probably tighten it further to hold a seal I made the guess that the high pressure was not really helping. So I decided it'd be better to limit myself to 15. Seems to be working better; I still have my apnea events being prevented or immediately reversed but now the machine never gets quite so aggressive to do it.

starting at 4 would require too much time to reach the effective pressure

The machine ramps up awfully fast, I'm not sure that's as big a deal.

[mrmagloo]

In the most basic terms, the idea is to set the goal posts on the minimum and maximum pressures to narrow the range that provides the best therapy. For instance, some people simply cannot get enough air on the low side. I have mine set at 10 cm with no ramp, which under every circumstance is the lowest acceptable level. However, on the high side, I know my 95% is around 17.0 cm, so I set the high end at 18 cm, knowing that above that, it's being caused by a mask leak. The greater the pressure over your 95%, the more likely a small leak will become a larger one that will not resolve itself. As such, it's all about fine tuning to help the machine stay within closer proximity to your average best therapy range.

[Gideon]

Honestly 4-20 does work for a very small group. That is not the norm. Proper settings also depend on the brand, actually the algorithms the brand used.
Reed is more aggressive and as such can be further away from what is needed than other brands. PR brand machines definitely tend to require higher pressures to achieve optimum results.

[Sleeprider]

We know auto CPAP works better and is more comfortable when set to a narrow range of pressure that is effective and does not disrupt sleep. Some additional interpretation is needed to assess why a machine may be increasing pressure or events breaking through in spite of optimization. Flow limitation and positional apnea are two significant influences to therapy efficacy that may need setting adjustments or use of positional aids, that can allow greater efficacy at lower pressure. The auto algorithms are a substitute for optimizing therapy. Fixed pressure or a narrow range of pressure (when done right), is usually much better than default auto settings.

[factor]

I regularly see people post things like "Don't worry about setting your pressure. The machine is automatic and will adjust as needed." 

I think most on this forum know the default settings are not good enough.  Its the DMEs and clinics that dont know they should change things.

[SarcasticDave94]

Yep, good point. OK then this needing to edit defaults is maybe geared more towards the RT at the DME or illegible scribble doc script writer pro 2.0.

Why don't they change it from defaults? Because they can pack in more signatures on the script pad for many duped PAP users on those oh so easy defaults than they could if they took an extra minute to decide something other than default would be good for Ralph My Lunch or Bill Payer III. The more scripts they send, the bigger the boat payment at month's end.

[ICEMAN]

https://www.resmed.com/en-us/healthcare-...echnology/

AutoSet™ algorithm
ResMed’s renowned and clinically proven AutoSet algorithm – one of the most clinically published algorithms in the field of sleep-disordered breathing – continually monitors each patient’s unique breathing pattern on a breath-by-breath basis, making automatic adjustments for comfortable therapy throughout the night.

When AutoSet detects an event, it doesn’t just apply a fixed pressure response, but instead assesses the severity of each event – whether it’s flow limitation, snoring or apnea – before determining and delivering the ideal, lowest pressure solution. After breathing stabilizes, AutoSet gradually decreases the pressure, while continuously monitoring for recurring events. Through it all, patients remain comfortable, receiving the pressure that’s right for them, at any given time – no more, no less.

And, because research shows that women with OSA experience more upper airway resistance and flow limitation, 1 we’ve designed a special AutoSet for Her algorithm that offers a more sensitive response. It also provides more subtle changes in pressure to minimize disturbance, and automatically adjusts the minimum pressure if multiple apneas occur below a certain threshold.


ICE

[Geer1]

It is pretty easy once you realize what makes these machines "automatic".

These machines are automatic in the sense that they adjust pressure on their own. They are programmed to raise pressure AFTER bad breathing occurs (apnea, hypopnea, flow limitation, snore etc) and then lowering pressure if no issues are present. These machines are not proactive and they do not determine an ideal setting and use it, they just increase pressure when your breathing is poor and try to reduce it when your breathing is good.

The premise of CPAP is simple, pressure helps hold your airway open. If you require 8 cm pressure for this to occur then using a machine that produces 8 cm no matter what will be more effective then a machine that produces 6 cm, increases to 8.5 cm because you are having apnea, then decreases to 7.5 then back up to 8.5 after more apnea and so forth.

Where APAP comes in helpful is that most people do not require the same pressure all the time. Pressure required depends on sleep position, sleep stage and other factors. APAP allows you to set a minimum pressure effective the majority of the time and then have the machine respond to deal with the rarer cases you need more pressure.

Using a wide open setting and not determining an effective minimum pressure means that part of the night is wasted with inadequate treatment as these "automatic" but stupid machines try to use pressures lower than what is effective. Maybe one day they will have artificial intelligence machines that determine an ideal setting and then use it but that is not what these machines do so that means a human still needs to interpret the data and determine ideal settings.