Problems w/ Electronic Continuously Regulated Pressure -Why?

[oldschoolcpap]

So this one might be hard to explain clearly...

Note: I am NOT talking about C-Flex, A-Flex, EPR "Easy Breathe" or any other sort of deliberate exhale pressure relief system.


What I am talking about is an anomoly caused by electronic pressure monitoring which causes the machine to "feel" as though it's backing off when you exhale. What it is really doing is continuously regulating the pressure and thereby reducing the pressure just slightly to compensate for the increase caused by my exhalation. Then the machine races to try and ramp up as I inhale and there is a sudden decrease in the monitored pressure.

The offending unit is a Puritan Bennett GoodKnight 420G.

I come from old school CPAP machines. I've reverted back to my old HealthDyne Tranquility Quests as my primary CPAP machine. The HealthDyne old style units is calibrated with a meter and by adjusting a screw. Then they forevermore pump forth the set pressure no matter whether you exhale, inhale, or leave the unit running with the headgear off. This causes the sensation that the pressure increases when you exhale. Simply put, your exhalation combined with the machines pressure equals a perceived increase in pressure (if not an actual one.)

Many people don't like the sensation of breathing against the machines push. Hence the rush to develop these newer generation machines with all kinds of deliberate breathing compensation. But for me, I am VERY used to the older type of machine.

A couple years back I decided I needed a small travel machine. I ended up with a Puritan Bennett GoodKnight 420G. unfortunately the PB GK 420G does not work for me at all! And I would like to figure out why for my own sanity and future CPAP purchases.

Now I didn't initially realize there was an issue because I used the 420G only when travelling. Note that I also have narcolepsy (yeah, great combo with sleep apnea) and I was not driving on my trip. So as per the Doc's instructions, I left the meds at home. Not surprisingly perhaps, I was rather tired on my trip. But I simply put it down to jetlag, the fact that we set a hectic pace, and that I was off the meds that usually prevent me becoming drowsy. When I got home, the machine went in the closet. Frankly I hadn't been terribly impressed with the way it felt in use. It heats the air passing through it uncomfortably and never really felt like it was giving me the same pressure as my older unit. But as I said, I really hadn't clued in that there was an actual problem yet. (Hindsight sucks.) I just thought it felt odd.

So a while later when my Heathdyne died, I was forced to turn to the PB GK 420G. Within 3 days using the 420G I was a complete zombie. Clear proof the machine was just not doing the job.

My equipment supplier managed to find me another Healthdyne thankfully and then fixed my old one. So I have a spare and my old faithful back. But they cannot last for ever unfortunately. I also still have the problem with the fact that they are a bit large to fit in luggage when travelling.

So now I put everything together and realised that I'd always felt like despite the fact that the 420G was saying it was putting out pressure, that it was just too easy to breathe. Generally I had an "is this thing on?" reaction. I even had the wild notion that my breathing was stronger than the blower in the 420G.

So then began the investigation. What was wrong with the PB 420G? My equipment supplier tested it (right on the counter in front of me) and even with me hooked up. It performed perfectly. The test meter and the unit both continued to indicate the set pressure while I breathed in and out. So given the fact that the unit was testing fine and I'd had it a while, they refused to take it back of course. This despite the fact that it does nothing for me.

One plausible explanation I was able to come up with was that when the machine slows slightly (regulating the pressure in compensation) during exhale, there is a void (or lag) before the machine can recover and then ramp up enough to compensate for the inhale pressure drop. That lag time may be causing the machine to be ineffective at the time I need it most. I have been unable to get a sleep diagnostic performed with me using the 420G to confirm that explanation. So it's a theory. But I'm still left with a question-mark.

I'm stuck with a CPAP that doesn't work for me. No actual (factual, real, tested, documented) explanation as to why. And I can't get ADP funding again for another couple years. I'd be much happier if I could just get some credible answers about why this machine (or type of machine) doesn't work for me. Also, I'm very afraid of purchasing a new unit because I don't know if they will present the same problem.

There is no doubt that I am part of the problem. For some odd reason, I can't handle that auto-regulation feature. That I can't adapt because I've been using the old machines so long. But I'd still like to understand why that's the case, so that I can hope to find a good solution next time I buy. My Doctor indicated that this was being studied, but has failed to provide any further information.

So there's 3 questions after all of this:
1. Does anyone else have this problem?
2. Does anyone have any credible explanations why this electronic-constantly-regulated-pressure doesn't work for me?
3. Anyone suggest a small travel unit that can emulate the old-style constant blower pressure feel?
Machines I'm curious about:
- AEIOmed Everest 2?
- ResMed Escape II (feature to turn off EPR) - but does that solve my problem or does it still auto-regulate it's pressure continuously?

I am really hoping to find a travel sized CPAP that can perform the same task as my trusty workhorse Heathdyne Tranquility Quests. I'm pressuming that I need a machine that only does an electronic altitude / power frequency / pressure test and calibration at startup and thereafter just dumbly pumps out the same rate.

Thanks in advance for reading and for any help.

Sincerely,
OldSchoolCPAP

[ozij]

I think you may be referring to this.
This a timesnapper image of a messy moment in the night for me.
You can see my Puritan Bennett 420E's pressure line (bottom, blue) responding when my breaths (inhale and exhale, top, blue) becom very deep.



How much pressure do you need? When I had to choose a machine, my RT commented that the PB had a weak motor, but would be OK for my lower pressure needs, she would have doubts about it if I needed high pressures.

I wonder if your problem may be a solved on a more modern machine, with data tracking capabilities. The newer machines, with software, give you much information about the relaionship between your pressure and leaks and events. Maybe a slightly higher pressure on the 420G would help by ensuring higher pressure as you ehxale?

O.

[dsm]

Yes you are quite right that the Tranquility Quest machines plus the F&P HC2xx range, the early Remstars & many of the other older machines did just run their blowers at the constant speed & deliver the set pressure without disruption.

But, then in the early & mid 2000s cpap machines started including pressure sensors at the air exit ports. They did this as part of a need to be able to do things like altitude compensation plus pressure monitoring. Autos had already added pressure sensors plus started adding flow sensors as they needed this data for the algorithms to work. The flow sensors were needed to detect hypopneas & flow limitations (they could not do that with out the flow sensors).

One side effect of the use of a pressure sensor was that when a patient breathed out, the combined pressure from the patient and the machine got detected at the air exit of the machine and the pressure *could be lowered* lowered (not all the early machines did so). This was beneficial to anyone on higher pressures (14 cmH2o +) as it reduced the potential for a mask to leak on exhale for these folk & back then with the masks available it was essential. Compliance due to poor mask effectiveness was perhaps the single biggest reason for people quitting cpap therapy.

For anyone on lower pressures, the early constant speed machines were great. I really liked the F&P HC2xx range for this very reasons (one demo I used to do was to blow as hard as I could into the airhose with the HC221LE at 13 cmH2O, and point out that the motor did not change pitch in the slightest, at anytime, it just rammed out the air at the set pressure).

But, there was another development that came into lowering cost of manufacture & providing better control & that was the introduction of DC brushless motors into cpaps. Once they were unleashed size of the blowers *then the cpaps* began to shrink. The culmination being the Puritan Bennett PB42x models & the Resmed S8 models. Prior to DC brushless motors, the blowers were more like small vaccume cleaner motors (I would not be surprised if Hoover was the common blower manufacturer ).

Anyway, nowadays almost all modern cpaps have exit air pressure sensors & blower speed regulators. The most advanced blowers are fitted with dual impellers (one fan at each end of the blower motor shaft - delivers same air at half the speed of the generation before - the dc brushless motors have unbelievable torque for their size - to get an idea of just how incredible these motors are, go to a model aircraft field & ask to see an electric model helicopter flying upside down just above the ground for anything up to 15-20 mins (if the pilot wanted to do it)).

So yes the good old Healthdyne Tranquility Quest & HC20x are rock solid (albeit a bit noisy by today's standards) but deliver constant air pressure.

DSM

[johnnygoodman]

Howdy,

They aren't listed on the website, but CPAP.com has two brand new Tranquility Quest units available for $200 each.

If you are interested, call 1-800-356-5221, reference the CPAPtalk thread and ask for Eva.

Johnny

[oldschoolcpap]

My pressure is relatively low. 9cfm. Which is probably why I prefer the constant rate.

Are there any newer small form brushless units that can be made to emulate my older machines constant flow?

The 2 units I've been looking at as possible candidates are the ResMed S8 Escape II or the AEIOmed Everest 2. I've found very little technical data on the Everest 2. I do know that the ResMed S8 Escape II/Elite II have the ability to turn off the EPR feature. But turning off EPR doesn't necessarily get rid of the pressure regulation effect that seemed to cause problems for me.

As for the PB 420G, yes I really did have the feeling that it was rather weak. I'm a pretty big guy (6' 6" and over 375lbs) so I have a rather developed set of lungs. Perhaps that really was part of the issue.

Obviously I'm going to have to do a trial with whichever machine I select next to ensure it's going to work for me. But if anyone can tell me about machines I really should look into, or machines I should probably avoid, it would be quite helpful.

[dsm]

My pressure is relatively low. 9cfm. Which is probably why I prefer the constant rate.

Are there any newer small form brushless units that can be made to emulate my older machines constant flow?

The 2 units I've been looking at as possible candidates are the ResMed S8 Escape II or the AEIOmed Everest 2. I've found very little technical data on the Everest 2. I do know that the ResMed S8 Escape II/Elite II have the ability to turn off the EPR feature. But turning off EPR doesn't necessarily get rid of the pressure regulation effect that seemed to cause problems for me.

As for the PB 420G, yes I really did have the feeling that it was rather weak. I'm a pretty big guy (6' 6" and over 375lbs) so I have a rather developed set of lungs. Perhaps that really was part of the issue.

Obviously I'm going to have to do a trial with whichever machine I select next to ensure it's going to work for me. But if anyone can tell me about machines I really should look into, or machines I should probably avoid, it would be quite helpful.

The quest does use brushless DC motors but they are on the biggish side. The PB318 range used the vacuum cleaner style motors. DC brushless blowers started being used in the late 1990s & early 2000s but by 2003 they started shrinking them - Puritan Bennett were one of the pioneers at shrinking the motors. The motor in the PB42x series is so tiny you can hardly believe the blower & motor can deliver 20 cmH2o.

I sold a as new Tranquilty Healthdyne Bilevel to someone last week & he is very happy with it. I offered him a choice of that or a Healthdyne Auto but recommended the Bilevel. The Quests still good machines (I have 2 I am selling - but I am in Aust). The ones Johnny mentions might be open to some negotiation.

DSM

DSM

[GumbyCT]

When was you last Sleep Study? I am wondering if your pressure needs have changed?

[rested gal]

Until you are able to find a machine that suits you, what ozij mentioned is what I'd do... raise the pressure on the PB 420G and see if a little more pressure makes that machine work better for you. I'd raise it one or two full cms, if it were me.

If you don't have the Provider manual (clinical manual) for the 420G, I'll be glad to email that to you. Will need your email address. If you register for this message board, you can use the Private Message feature to PM me your email address. "Guests" don't have PM capability.

[oldschoolcpap]

rested gal, thanks, I have the clinical setting information. I did try raising one level before, but not 2. It didn't seem to have any effect. I believe the problem has more to do with the lag time (response) between the changes in pressure. As the machine keeps changing it's blower speed to "maintain" the pressure, it cannot seem to ramp back up fast enough in the inhale phase after spooling down in the exhale phase to actually maintain consistent pressure. The effect makes it feel like there is no pressure. Or is if I am pushing the machine, rather than machine pushing my airway open. With the old style units I have there is a definitely feeling of pressure exerted on you. I might try it again with 2 level increase though.

GumbiCT, My last sleep study was shortly before getting the PB GK 420G. My results were little changed from the previous study. I currently have no issues sleeping with my Tranquility Quest CPAP machine. I wake refreshed and happy. The problem occured only with the Puritan Bennett GoodKnight 420G that now resides in my closet unused and definitely unloved. It's relatively safe to presume the machine is to blame (or the way in which it functions, differing significantly in feeling from my Tranquility Quest.) Unfortunately the sleep clinic refused to perform another study to show what was happening while I was using this machine. My Doctor indicated there have been others with similar issues and that the issue was being studied. He has provided very little information (despite his promises and my repeated requests.)

I was led to believe there are (or were) other small units on the market that can provide an experience similar to the Tranquility Quest. But I have yet to find any documentation or specifications on any machines that indicate a forced fixed flow rate mode (or something to that effect.)

DSM, I may indeed pick up more Tranquility Quests. I would be quite happy to continue using them at home. Why mess with what works? But travel is becoming an increasing problem as airlines reduce carry ons and many airlines are specifically including CPAPs in carry on allowances where they used to be exempt like purses and jackets. So I really do need to find a small machine that will travel well. If I can find one that will give me a Tranquility Quest-like experience either through settings/reprogramming/hacking/modification the end result is what matters.

[dsm]

oldschoolcpap

I can't think of a modern lighter machine that blows like the older ones do. I would lean towards a basic S8 model - they have a pretty powerful blower - the S8 IIs have an improved blower (quieter - even though I always regarded the older S8s as quiet).

But these do have the pressure sensor, but am of the opinion the resumption of pressure should be as fast as your breathing.

Can you get to try one ? - even the older S8 Escape (very cheap to buy used). They are an excellent travel machine even if a bit heavier than the PB420G.

Good luck

DSM

[oldschoolcpap]

DSM, The RM S8 Escape II was certainly on my shortlist. I am hoping I might get a trial/rental units through one of the equipment providers in my area.

The ResMed site mentions EPR on almost all of their units (except the S8 compact) but only the Escape II and Elite II mention being able to disable the EPR. EPR worries me because it's more or less a deliberate version of my problem. Which might amplify the effect for me.

The other machine that sparked my curiosity was the Everest 2. But I haven't found much detailed info on it.

[dsm]

oldschoolcpap

You may find these machines (disassembled) of interest - includes the Healthdyne set I had.

http://www.internetage.ws/cpapinfo/menu2ok.html

Cheers

DSM

[oldschoolcpap]

DSM, that is actually quite interesting. I would have thought the blower in the Quest would take more space. I'm surprised to see how much space the transformer and that massive capacitor take up. The blower on the 420 looks very tiny.

[oldschoolcpap]

Just an update, I ended up getting a Phillips/Respironics PR System One REMstar Pro C-Flex+

I'm not actually using the C-Flex feature. Just regular CPAP therapy. Which is going quite well.

One of the primary reasons for upgrading to the higher model was the auto altitude compensation. I travel a reasonable amount . Having a machine that can cope with that seemed a good idea at the time.

Ironically after purchase, I'm afraid to take it anywhere because it cost so much! Plus I have never used a humidifier. Respironics doesn't offer a blower-only carrying bag. I ended up finding a camera bag that fits it well enough and will provide good protection. But has the downside of making it all the more attractive looking to theives who might presume it's an expensive camera. My anxiety wasn't reduced even after making up some fairly noticeable medical device tags for the bag. The end result only seemed to scream even louder "steal me." So I still travel with the old Tranquility Quest! I must be nuts. But I actually really like my new unit and don't want anything bad to happen to it.

I changed providers for my new CPAP. So far I'm fairly pleased with the new provider. They actually offered to give the Puritan Bennett PB GK420G a good looking over. They ended up discovering that the previous provider had failed to correctly calibrate the unit. I've only slept one night with the unit since it was correctly re-calibrated (still having difficulty completely trusting it after so much trouble) but it was actually a restful night. I've toyed with the idea of trying it out for a couple weeks. But so far have yet to commit to that. I still think the PB is a significantly inferior machine to both the Tranquility Quest and my new REMstar.

Apparently the GK has a rather bad provider manual and there's a small little subtext note that if you fail to read it, you won't actually callibrate the machine correctly. My new provider said this was a really common issue with this machine. The machine may give every indication the new setting is saved. But when the machine is turned off and unplugged, the callibration will revert if it's not been done correctly! Nasty. Anyone with a Good Knight should insist on seeing their machine callibration and on seeing the callibration verified after an unplug!

I still use the old Tranquility Quests at my Parent's house whenever I visit (fairly frequently) which avoids having to lug a machine home. I've started a rotation scheme to ensure each machine sees some use to try to prevent decay.

Thanks to everyone who contributed.

[So Well]

This causes the sensation that the pressure increases when you exhale.

This suggestion I am going to make is not an orthodox technical answer.

When I first started on CPAP, sensations caused problems such as mild anxiety that interfered with sleep.

Finally I bought a different machine with software and successfully worked on getting my AHI down.

Then I could see every morning that the machine was allowing me to breathe well throughout the night.

After seeing these good results for many mornings, I gained excellent confidence in the process, the mask, and the machine settings.

This confidence eliminated the mild anxiety and no longer was I aware of the machine whine or the pressure.

Software = data = process measurement = process optimization = data showing good efficacy = confidence = lack of worry about sensations = good sleep.

Software. Try it. You will like it.