First Post: Help analyzing my OSCAR data & other questions

Hey guys, first post in here, hopefully I did it all right, but I’d love to get some Insights/analysis, settings advice, and questions answered. I know this first post is a bit long but I wanted to give as much of the picture as possible, but if there is something you guys need to know to help further just let me know. Excited to try and help myself with your guys help.

Gear:
Machine: ResMed VPAP Auto IPX1 (Model: H5i)
Humidifier attachment: ResMed: Model S9
Mask: Full Face Phillips Respironics
Tube: ResMed Climate Line (S180408)


Background:

I’m a bigger guy 6’7” ~390lbs, so Obese, High Blood Pressure, past Heart issue, and Sleep Apnea, I’m the perfect storm. I’m actively working on the weight part of the equation and now actively working on the Apnea part of the equation.

I did a sleep study about 20 years ago because my partner at the time wanted me to address my snoring and breathing issues, I was reluctant, but they diagnosed me and gave me a machine. I don’t recall the details of the diagnosis or the machine settings. I was young and dumb. The straps on the mask after about a year’s worth of usage triggered an outbreak of psoriasis on my scalp where the bands were. The whole experience made me throw it all away, pissed that I now had a second disease because of this first disease. So I spent years just snoring away and ignoring it.

Fast forward to probably 7 years ago, I had a heart incident that put me in the hospital and as part of that they gave me a Variable CPAP machine in the hospital to help me rest and ease my heart. After I got out of the hospital I immediately bought a second hand version of the same machine they had me on, got a mask, heated tube, and used it for a few months during my recovery. Was early in a marriage and ended up falling off of using it, mostly for insecurity reasons.

Fast forward to now, my heart doc asked me to reconsider and get back on it because it’s good for my heart even though I’m better. I can tell my sleep is bad, my snoring is bad, and while I don’t recall my original diagnosis or settings, I feel pretty confident I still have sleep apnea based on well every partner who’s shared a bed, and the fact I’ve recently woken myself up gasping for air, sometimes loudly and dramatically. I am waiting for an appointment to do a new sleep study to help dial this in even further and probably upgrade gear, but meanwhile I’m taking some of this into my own hands, hopefully with some help from y’all with my old gear.


Night 1 (1/18/24):

Settings:
Humidity: 4 (after first rain out, OFF)
Tube: 86
Ramp: Off

Advanced Settings:
Mode: CPAP
Set Pressure: 15
Max Ramp: 25 min
Start Pressure: 7
EPR: Off
EPR Level: Off
Mask: Full Face

CPAP Settings: https://i.imgur.com/4TU5L9b.jpg
Options Settings: https://i.imgur.com/sPIMCRv.jpg

Overview: After deciding to get the machine back out, I did a lot more YouTube and message board reading and feel alot more educated this time around and learned about Oscar, which got me back on the saddle because I wanted to see how crappy my charts would be. Overall it was rough, lots of waking up through the night, rainout reasons, mask leak reasons, needing to pee in the night reasons, uncomfortable reasons, trying to find the right position or pillow situation. I woke up not feeling refreshed but still determined and I wanted to see the data. Things that stood out to me, I thought I’d see where my pressure settled in, maybe like a 12.3 or 14.6 or something weird and I’d use that to dial in the pressure to a less wide of a range. Instead I saw 15 flat-lined all night. From what I understand on how CPAP is suppose to work is you have a Start Pressure, say of 8 (and maybe a ramp up to it, but I have that off). Then you have a Max Pressure, say of 20. It would get to 8 then each time you have an event or snore it increases the pressure, slowly, then worst case it may get to 20, but if 12.6 stops the events then it would spend most the night around there. My settings have a Start Pressure, a “Set Pressure” and a Max Ramp. I thought Set Pressure would be the “Max Pressure” and set it to 15. I don’t have a Max Pressure setting in CPAP mode on my machine. What I don’t have is a Max Pressure setting. So instead of working it’s way up, it just went to and stayed at 15. But I wasn’t sure yet if that’s because my body needed something more than 15 and decided to take it to the max tomorrow.



Individual Breaths: https://i.imgur.com/X1kWZzc.png


Night 2 (1/19/24):

Settings:
Humidity: 0.5 (after first rain out, Off)
Tube: 86
Ramp: Off

Advanced Settings:
Mode: CPAP
Set Pressure: 20
Max Ramp: 25 min
Start Pressure: 7
EPR: Full Time
EPR Level: 3
Mask: Full Face

Overview: My Main changes was to attempt to start with the lowest possible humidity setting to see if that would allow some humidity but not soak me (didn’t work). I left the Ramp setting off, but brought back EPR and set it to 3. My logic here was after looking at the Flow Rate individual breaths on the first night I was seeing flat caps at the top of the breath and after watching some videos on how EPR helps get that more towards a normal curve, I thought I’d just make that the main change to see if that worked (it seems to have, see below). The only other main change was move Set Pressure to 20, I still wasn’t sure if it was a coincidence that I spent the first night at 15 the whole time, or maybe my body needed more, say 16.3 but couldn’t get there and I’d see it work as I expected it to where it just goes as high as it needs and not more. So I set it to 20 figuring maybe it doesn’t get there. (Turns out I was wrong, spent the night at 20, more on that in Questions section). Overall though, it was a better night of rest than night one. I only recall getting woken up twice, mostly due to noises and/or water splashing my face, if I could get that under control and find where my pressure should actually be, I feel like I’d be getting somewhere. I think the EPR experiment was successful. I was going to try backing it down to a 2 in a future experiment to see if my breaths still curve out well. But that can wait if I’m moving to VPAP tonight. I don’t want to many variables and I want to get to something close to right by the end of the weekend because I want to stop making so many tweaks without giving them more time over a week or two before adjusting because I know it’s not good to keep adjusting because you could develop other issues. Which is why I’m trying to get into the right ballpark quickly so we are at least playing ball instead of spending 2 weeks in the wrong area. I left Mask Pressure chart up on Oscar screenshot, because maybe I just don’t understand the Pressure Chart and Mask Pressure has better data on where my settings should be? I also left Snore on because I have a question about it below.



Snore & Mask Pressure: https://i.imgur.com/cBGIrLQ.png
Individual Breaths: https://i.imgur.com/RRxrbor.png

Questions:

1. I have 3 modes on my machine (CPAP / S / VAuto). I set it to CPAP to eliminate variables at first. After my experiments night 1 and 2 confirmed that “Set Pressure” is indeed not the same as “Max Pressure” and it seems my CPAP mode doesn’t have a Max Pressure, and spending the whole night on say 15 or 20 does not seem like how I should be doing this, I don’t want to just stay at either a high setting or the wrong setting all night if my body didn’t need it. My question is, should I move to VAuto mode because this machine doesn’t operate like most others do in CPAP mode because it’s a VPAP even though it has a CPAP setting? Because it has a Min EPAP setting and Max IPAP setting. If yes, can you help me understand what the settings should be, particularly the weirder ones like PS, TI Max, TI Min, Trigger, Cycle, etc.

VAuto Settings 1/2: https://i.imgur.com/gqwxw07.jpg
VAuto Settings 2/2: https://i.imgur.com/GBGeXEz.jpg

2. I have a Climate Line: S180408 heated hose. Is there a way to tell if the heated hose is actually working? I have it set to Manual in the settings (other options: Patient and Auto). I have the temperature set to 86 F (highest possible). It’s not even warm to the touch and I’m not sure that it’s suppose to but even with humidifier off, I’m still getting a lot of moisture in the tube and mask (which I assume is from my breath) and am getting woken up at least 2-3 times. I feel like maybe it’s not heating or I botched a setting. Anyone know the difference between Manual, Patient, and Auto, and which one I should be on? I’ve been on Manual but tried Patient for first part of night 2 thinking maybe that setting means use the setting set by the Patient in the basic Settings on Home Screen. Neither seems to be helping keep droplets out, my thought was trying Auto tonight unless someone can help me triage this.

3. Is it wild that my AHI is under 1, even on my awful first night? I don’t know what I expected, but it wasn’t a number that low. Let’s be real

4. Is it weird that even on night two with such a high pressure setting that I’m still snoring? Or I assume I am because I see so much activity on that chart, but maybe that’s normal even if you are not snoring? I have not recorded the audio of the room while I am sleeping yet to verify this but am I legit snoring all night even with all this…

What is the ambient bedroom air temperature?

Are you sleeping on your back? If so is that normal for you and do you ever sleep on your side?

Are you experiencing any nasal congestion at night?

GBRinATX wrote: ↑

Sat Jan 20, 2024 3:04 pm

should I move to VAuto mode because this machine doesn’t operate like most others do in CPAP mode because it’s a VPAP even though it has a CPAP setting? Because it has a Min EPAP setting and Max IPAP setting. If yes, can you help me understand what the settings should be, particularly the weirder ones like PS, TI Max, TI Min, Trigger, Cycle, etc.

I suggest VAuto mode as a starting point.

When in CPAP mode the machine is working as designed for a fixed pressure machine. It is working like any cpap fixed single pressure machine. It is working normally. When you set it to 20 that is what you get all night if not using the ramp.

The settings that I highlighted in red....use the factory defaults. They work very well for the majority of people using this machine. Don't go screwing around with them just yet. BTW I use a slightly newer version of this machine so I am quite familiar with it.

GBRinATX wrote: ↑

Sat Jan 20, 2024 3:04 pm

Is it wild that my AHI is under 1, even on my awful first night? I don’t know what I expected, but it wasn’t a number that low. Let’s be real

No, not wild and doesn't surprise me with the fixed cpap pressure settings you have been using which are quite high....you probably don't need that much pressure. Overkill probably at least in terms of the OAs and hyponeas.
Not sure about the snores or flow limitations at this point. Need some data to get a better idea what is going on.
That much snoring and FLs isn't normal unless maybe the water in the hose/mask is making the machine think you are snoring.

May I make some suggestions for tonight's VAuto settings that I think will do a better job for you?
Mode...VAuto
Minimum EPAP....7
PS....4
Maximum IPAP....25 (it won't go there without a good reason)

Those "weird settings"....that I colored red above...use the factory defaults and if you don't know them or have changed something and don't remember there is a setting choice in the menu to "restore factory defaults"...do that and then go in and make the EPAP min at 7 and max IPAP at 25 with PS at 4.

Go here and read posts number 2 and 3 where I talk about various ways of dealing with rain out in the mask or hose.
http://www.cpaptalk.com/viewtopic/t9403 ... -road.html
And the heated hose won't necessarily feel all that warm to touch because even at the max of 86 degrees it is still going to be cooler than your body so it is going to feel cool because your body is at least 10 degrees warmer.
More about the rain out situation once I know you bedroom temp.

First, thank you so much for taking the time to read and respond to help me out, I truly appreciate it!

What is the ambient bedroom air temperature?

Just measured next to the bed and it's 71 F, I don't change the thermostat overnight so it should roughly be like that through the night. Right now my hose temp is set as high as it can go (86 F), I'd love to get humidity back on, but last night at the lowest setting (0.5) it was still an issue. So I'll take any advice you got. I could bump the thermostat up another degree or two since it is kinda cold, but typically I keep things around 70, winter or summer so I'd like to get it working around that temp.

Are you sleeping on your back? If so is that normal for you and do you ever sleep on your side?

Predominantly I am a side sleeper and flip flop between sides. It's rough on my arms and hips, sometimes as after many hours it gets uncomfortable. So I do mix in some back sleeping if I'm masked up. So I'd say last two nights I spent a decent amount of time on back, and both sides. When on my back though, I go down to 1 pillow, I'll swing a second pillow under my head if I'm going on my side.

Are you experiencing any nasal congestion at night?

Nothing note worthy, I'm a mouth breather and I'd love to just breath through the nose, and I may try to re-train things down the road. I do notice when I'm masked up I can breath much better via the nose, but while going to sleep and using the machine I feel like I'm not getting enough oxygen if I try to go to sleep with my mouth closed through my nose and after a few breaths my body freaks out a bit and I have to take a breath via the mouth. Sometimes when I first mask up and am settling in, I have to move my jaw to create a leak in the mask and take a more full breath with outside air a time or two just to get my body to settle down.

Other Notes:
1. Just finished reading article 2 & 3, I saw the recco for the barrel cozy for nose breathers. Is there something like that for full face masks like the AirFit F30i?

1. I also ordered a hose cover yesterday which should arrive before bed tonight and I'm going to get that on the hose too, at this point I'm trying anything and everything. Link: https://www.amazon.com/dp/B089QQBWBR?ps ... ct_details

2. I do have my machine on the floor, I have a night stand and the top is about level with the matress top, and there is an opening about a foot lower that could also hold the machine if you think I should move it to even with the matress or just below the matress vs on the floor. My primary thought around the floor was to get some of that water to drain down into the machine vs draining down into say a dip in the hose and collecting there until it accumulates enough to cause problems. But at this point I'll try anything.

3. When I side sleep towards the edge of the bed, hose is coming off the front of the mask and just heads down off the bed, When I'm flipped away from the edge of the bed, hose placement typically is above head, traveling across the top of the pillow towards the edge of the bed, then off towards the floor right now. When on my back, goes towards edge of bed between head and shoulder then down towards the floor. I'm looking at trying the ResMed AirFit F30i after I meet with the doctors and do my new study and am thinking about getting an AirSense 11 Autoset. I say all this as we are thinking about condensation, accumulation, and hose placements through the night. I don't use any kind of hose hooks off the wall or headboards currently.

One other note: I did the factory reset as you recommended because I did get it second hand a few years ago and unsure if the settings were changed.

One thing I noticed is on the home screen settings Climate and Humidity use to be two separate controls, now they are tied together into one and set to 86. Also Ramp is on, do you think I should turn Ramp off or leave it on for tonight's test?



Other question is should I change Start EPAP, default setting is 4.0. Below is the full settings as of now.

General Settings:
Climate CTRL: 86 F (No separate Humidity setting)
Ramp: 20 Min

Advance Settings:
Mode: VAuto
Max IPAP: 25.0
Min EPAP: 7.0
PS: 4.0
Ti Max: 2.0
Ti Min: 0.3
Trigger: Med
Cycle: Med
Max Ramp: 45 Min
Start EPAP 4.0
Mask: Full Face

Last night my ambient bedroom temp got down to 61 degrees and right now it is 63 degrees (we've been in the deep freeze all week). I got a little gadget that gives me a high and low temp reading (as well as current) along with a high and low humidity setting (as well as current).
I have my humidity set to max of 8 and I didn't have one drop of condensation and my machine is level with my mattress.
That old wives tale of setting the machine on the floor doesn't work so great for condensation at the mask level because most of the time the real annoying condensation is at the mask (our own exhaled breath moisture) level and usually that condensation just has some sort of up hill battle at the mask level and water can't run up hill. Take a hard look at where your hose goes...if there is uphill anywhere in the circuit the water will pool.

Do make absolutely sure to NOT overfill the water chamber. If you do the air going over the water in the chamber will blow the water right into the hose and at the pressures you have been using it can blow it clear up to the mask.

Make sure the hose is totally dry and not containing any moisture as well.

I do suggest NOT using the ramp because the settings I suggested should be quite comfortable with more air moving.
When people use that 4 EPAP (or ramp) they often feel air starved....they need more air moving. We won't suffocate at 4 cm but it sure can feel like we are suffocating.

General Settings:
Climate CTRL: 86 F (No separate Humidity setting)

Scratching my head on this one because you should have a humidity setting somewhere. I have used a S9 in the past but it has been years and I have forgotten exactly where it is or how to get to it. I need to do a bit of research on this unless someone else reading this has a better memory than I do.
Perhaps the humidity setting got turned off in the setup menu????? If it is off then it won't show up and you may need to go into the clinical setup menu to turn it back on.

Does your mask have some sort of short hose from the heated hose to the mask? If it does....take an old sock or two and cut a hole in the toe and run the sock over that short unheated hose. Secure with rubber bands on bread ties or whatever you can find to secure it in place. My mask has a 20 inch short unheated hose coming to the mask from the heated hose.
I have a hose cozy that is quite thick on it to help keep that air from cooling down.
A hose cozy on the heated hose is a waste of money but will save a little bit on electricity as all it can do is help maintain that 86 degrees in the heated hose.

More later...supper is calling.

I got a little gadget that gives me a high and low temp reading (as well as current) along with a high and low humidity setting (as well as current).

Love a link for that gadget, I was looking on Amazon at some of the ambient temp monitors because I was thinking that may help get more data in the mix here.

Does your mask have some sort of short hose from the heated hose to the mask?

No short hose, the heated hose goes from mask to machine. I do like the advice on filling the reservoir too full, it's possible I hugged that Max line too close, I'll back it down some tonight.

New Notes:

1. Ok found the setting to split the humidity from the hose temp. It was in the Clinical Settings under Climate Control. Default is Auto, and setting it to Manual split them back up.

2. Turned Ramp off from the general settings.

Settings questions for tonight:

1. Ok so Start EPAP: 4.0 setting under VAuto, should I leave this at 4 even though Min EPAP: is set to 7.0?

2. Now that I have split Tube temp and Humidity Setting: Should I go with Tube: 86 F and Humidity: 0.5? Or should I go higher on Humidity?

I'm excited to see data after tonight.

GBRinATX wrote: ↑

Sat Jan 20, 2024 6:26 pm

1. Ok so Start EPAP: 4.0 setting under VAuto, should I leave this at 4 even though Min EPAP: is set to 7.0?

You shouldn't be seeing 4.0 for minimum EPAP unless ramp is ON and to turn ramp off you have to go set the time for ramp to be at 0....that's how you turn ramp off ....set it to zero time.

GBRinATX wrote: ↑

Sat Jan 20, 2024 6:26 pm

2. Now that I have split Tube temp and Humidity Setting: Should I go with Tube: 86 F and Humidity: 0.5? Or should I go higher on Humidity?

Crap shoot on this one because I don't know why you are getting so much rain out.
With humidity set to 0.5 that is sure not much added moisture and it really makes me wonder if you are getting that much condensation from your own exhaled breath at ambient temp of 71 or if maybe you did over fill that water chamber.
But then you were using hurricane force wind pressure....
Try the setting of 2 and make sure the water level is just below that max line.
Maybe with the lower pressures used less chance of the air pressure blowing water into the hose...if that is where the water came from.

Was the rain out in the hose itself or just at the mask level? Did the hose make a lot of racket???

Let me go see if I can find that little gadget for humidity and room air temp. It was really expensive...like 9 bucks from Amazon but I have had it for years and years (been on cpap for nearly 15 years now).
Let me go check my past Amazon orders.

Found it. Bought it in 2015. Price has gone up a little but still not bad at all and it's still available which surprised me.
It's showing a little over 11 bucks but I am a Prime member...if you aren't a Prime member it will likely be a little more.

https://www.amazon.com/gp/product/B0013 ... UTF8&psc=1

You shouldn't be seeing 4.0 for minimum EPAP unless ramp is ON and to turn ramp off you have to go set the time for ramp to be at 0....that's how you turn ramp off ....set it to zero time.

Ramp is definitely off via General settings, but that min EPAP still there at 4. should I maybe just make it 7 to match the other setting Min EPAP?

Was the rain out in the hose itself or just at the mask level? Did the hose make a lot of racket???

Most of the noise was the mask joint to hose and around mask seal, but when I'd shift positions the water would come running from the hose itself.

I'll go with setting of 2 for humidity, I already made sure I was below max on reservoir and add the hose wrap for fun lol

Try to keep as much of the hose under your bed covers if possible. Let the covers help keep things warmer.

If you still doubt the heated hose working as it should you can try using a digital thermometer (like a digital cooking thermometer) and run the machine for about 15 minutes and then quickly remove the mask and stick the thermometer probe in the end of the hose where the mask was attached and try to catch the temp before it cools down. Gotta be really fast though because the machine will quit blowing pretty quickly once you aren't attached.

If the hose was used...I suppose it wouldn't be impossible for the heating coils to not be working. If it was a brand new hose it is highly unlikely that the heated hose isn't functioning properly.

Let's see how it goes tonight. I fully expect further adjustments are going to be needed but gotta start somewhere.

Good luck.

Pugsy wrote: ↑

Sat Jan 20, 2024 6:43 pm

Found it. Bought it in 2015. Price has gone up a little but still not bad at all and it's still available which surprised me.
It's showing a little over 11 bucks but I am a Prime member...if you aren't a Prime member it will likely be a little more.

https://www.amazon.com/gp/product/B0013 ... UTF8&psc=1

HA! was just going to link this as it's the one i have.

great minds and so on....

Thank you again for all the help yesterday, I'm back in my quest to fine tune this thing. Appreciate any help I can get on the journey.

Night 3 (1/20/24):

General Settings:
Climate CTRL: 86 F
Humidity: 1
Ramp: Off

Advance Settings:
Mode: VAuto
Max IPAP: 25.0
Min EPAP: 7.0
PS: 4.0
Ti Max: 2.0
Ti Min: 0.3
Trigger: Med
Cycle: Med
Max Ramp: 45 Min
Start EPAP 4.0
Mask: Full Face

Sleeping positions: Both sides, and back through the night.

Overview:
It was a rough night, pretty sure it took almost an hour or more to fall asleep. I had multiple disconnects due to condensation, sometimes I could just disconnect the hose, shake it out, spin it around like a cyborg cowboy and reconnect. Other times I had to shut down the machine, clear the tube and take the mask off and towel off myself and the mask. If all that wasn’t enough we introduced throat popping when trying to fall back asleep, I tried everything in my power to stop it but it seems involuntary and I cover it more in primary issues below. Long story short, I willed my way to 3:30pm to get as much data as I could and at least one section where I know I was for sure asleep then called it, took off the mask and slept without it just to get some sleep, adjust, and try again tonight.

Primary Issues:
1. What I will refer to as “pressure pops” in my throat. I don’t know how best to describe them but basically while trying to either fall asleep or fall back asleep after a disconnect like going to the bathroom, I’d breath normally for 2-3 breaths then randomly I’d feel a slight pop in my throat would make the mask jump almost like when pressure first comes on or goes off, sometimes it is a series of quick pops (like 2-3 in a row) that almost feels like how Chewbacca talks. It’s very had to fall asleep through. I noted some times down to look at the charts and I think I can see them data wise, you’ll see them below. My theory here is the pressure isn’t high enough and it’s something closing, probably when I’d normally snore.

2. Condensation issues persist. I started with Humidity on 1, Tube set to 86, Took the thermostat up to 72. After multiple times of having to disconnect the hose, shake it out, sometimes taking mask off and wiping it out, I took Humidity down to 0.5. I never got to the point of going to off because I gave up after about 3:30pm, but it would have been my next move. I think it’s probably more breath condensation than Humidifier but I don’t know how to get it to where I could get through 7-8 hours in a row. It’s by far the worst part right now.

The Deets:

When I was sleeping and caps looked the best
- IPAP: 20.72 (Red Line)
- EPAP: 16.78 (Green Line)



When I was sleeping but caps were flat
- IPAP: 19.78 (Red Line)
- EPAP: 15.74 (Green Line)



When throat had pressure pops
- When trying to fall back asleep after turning machine off, then back on
- IPAP: 11.18 (Red Line)
- EPAP: 7.18(Green Line)



Snapshot of entire night.

I am scratching my head over why you are having such a problem with rain out in the hose and mask.

It does make me wonder if the heated hose is working like it is supposed to.
You bought this equipment as used....was the heated hose also used or did you get a new heated hose by chance?

Until we can get you actually sleeping soundly for the bulk of the night and not fighting the rain out causing sleep disruptions it's really difficult to evaluate the pressure settings effectiveness and/or need for adjustments.

no I bought the hose new last time I was using the machine (few years back). I do think it's possible it's working as I'm not getting water build up in the hose to where let's say I tip the hose all the way south that a pool of water would come out. My current theory is I'm just breathing hot breath so heavily that it's building up. I'll be upgrading machines within a week or two once I get my appointment. I can live with the water wake ups more than I can not being able to get back to sleep because of the pressure pops. The new setup will have a new unit and a new heated hose so I can triage that more then.

Is there a way under the VAuto settings to just get the pressure to kinda be between say 16.5 and 21? There isn't really a minimum IPAP setting only a max.

Maybe the best I can do is just set the Max IPAP to 21 and the Min EPAP to 16.5 and then maybe adjust Start EPAP to say 16?

GBRinATX wrote: ↑

Sun Jan 21, 2024 4:05 pm

Is there a way under the VAuto settings to just get the pressure to kinda be between say 16.5 and 21? There isn't really a minimum IPAP setting only a max.

Maybe the best I can do is just set the Max IPAP to 21 and the Min EPAP to 16.5 and then maybe adjust Start EPAP to say 16?

You can try setting the minimum EPAP higher and you can set the maximum lower....like you mentioned above but you will need to lower the PS a bit if you want the machine to vary the pressure.

When minimum EPAP is say 16 and PS is 4 then you will get 20 on inhale and 16 on exhale.
PS gets added to EPAP to give you the inhale pressure.
The pressure won't vary all that much if the max is limited to say 21 but it can be done.