AHI at 16 on CPAP... help!

[MrMagoo]

Hi cpaptalkers,

I'm new here, this is my first post.

I was diagnosed with severe sleep apnea late last year after a sleep study confirmed it showing an AHI of 56.

I trialled a Philips Respironics Auto CPAP machine w/humidifier (5.5-20cmH2O Auto; Aflex 3) and a Remstar Mirage FX Nasal mask with good success for almost 2 months bringing my average AHI down to 6.8, whilst this was not under 5, my sleep clinician seemed happy with this.

My period on the trial ended, the machine went back and I started to feel horrible once again, you know the fog etc. I couldn't financially justify the $2,500 I was quoted to purchase the same machine new, I wasn't keen on purchasing a used older machine, so after considerable research I settled on a Probasics Zzz-Pap Auto machine by PMI, purchased from Respshop at a price that was more in line with my budget. I also purchased the same mask I used in the trial, a Remstar Mirage FX Nasal as I grew to like it.

I've set the machine to the same prescribed settings as above (5.5-20cmH2O), am using it in APAP mode with the supplied hose and have the humidifier running at 4.5

What’s concerning me is my average AHI is sitting at 16, I'm guessing this isn't so good? My current average pressure is 7.4 cmH20, average 90% percentile pressure is 6.9 cmH20, average leak LPM is 18.0, average large leak time is 1.0 min.

Does anyone have any recommendations of what I should do? Please don't tell me I've purchased a dodgy CPAP machine

Thanks in advance.

[flocof]

Hi from a fellow aussie. I cannot help you as I am new to cpap myself. I was diagnosed with 60AHI. I have been on therapy since early december and have only managed one night at 7 AHI all other nights have been well above that. I purchased a machine from the US from secondwind and am happy with it, but it takes a while to get the pressure right to lower my events. I do feel a lot better than I used to, and look forward to sleeping better. A forum member is helping and coaching me to tweak my machine to the right pressure for me. It all takes time and lots of effort and perseverance. Hopefully another forum member will give you the info you need and help you along.
All the best and good luck on your cpap journey.

[bdp522]

Too high a humidifier setting can cause nasal passages to swell, possibly you could crank it down a bit.

During large leaks the machine data is not reliable.

If it were me...I would start with the 90% reading of 6.9 which means that 90% of the night you were at 6.9 OR below. I would set the lower pressure to 7 and see if the AHI looks better. If it was still over 5 I would slowly raise the presure in small increments until I hit an AHI of less than 5.

Make only one change at a time. Wait a couple of nights (a week is better) before making any other changes. It takes time to adjust to any changes made.

As you adjust the pressure upwards keep an eye on leaks. More pressure can equal more leaks. You may have to readjust the mask to compensate for the higher pressure. Also watch for mouth breathing, higher pressures can make mouth breathing/leaking worse. Clues are dry mouth, high leak rates.

Brenda

[Emilia]

Your pressure range is wide open and should be reined in to a tighter range. With a 90th%tile of 6.9 you could reset your range to 5-10 to start off with and see how that works for about 5 nights. Generally, the rule of thumb is to take the 90th%tile reading and set pressures to 2 above and 2 below that number. A wide open range as you have now doesn't allow the machine to respond quickly enough to pressure needs when events occur. It also may induce central apneas. By bringing the range in more tightly, your machine can respond easily within that range. Try my recommendation for tonight and let us know how it goes tomorrow.

[bdp522]

If the OP hasn't been bothered by runaway pressures, and it doesn't seem he has been, there is no reason to lower the upper pressure. He makes no mention of super high pressure or pressure changes interrupting sleep. I think it is best to get the lower number as close to the needed pressure as possible to prevent as many apneas and hypopnias as possible. The machine shouldn't go higher than needed so the is no reason to limit the upper presure.

Brenda

[MDALE]

This may not fit your situation, but consider trying a thinner pillow so as to to keep your neck more in alignment with your spine. For many of us an overly bent neck seems to favor airway blockages and apnea events.

[MrMagoo]

flocof: Thanks for your post and support.

MDALE: Cheers, I might try that a bit later, thanks.

Too high a humidifier setting can cause nasal passages to swell, possibly you could crank it down a bit.

Brenda, I took your advice and pulled it back a bit. My humidifier has a range of 1 - 6, I originally had it set to 4.5, last night I pulled it back to 3, however I felt that the air seemed too cold but I persevered, I also woke today with a bit of a sore throat. I might try it at 4 tonight. Thanks.

Last night I also decided to adjust the lower pressure from 5.5 up to 6.5. I left the upper pressure alone at 20. My overnight AHI ended up being 25! I must admit with the lower pressure increased I felt slightly uncomfortable and it also appeared to give me a headache.

I wonder if I should split the difference and go for 6.0 tonight or am I making these changes too soon between each other? I'm just not sure I can handle the colder air, higher pressure when trying to get off to sleep and headache again.

[bdp522]

Are you sure you aren't mouth breathing/leaking? Could it be that the higher pressure caused more leaks?

Remember...ONLY 1 CHANGE AT A TIME!!!! After each change take at least a few nights to adjust before making another.

Brenda

[avi123]

Because you don't mention an effective pressure that your sleep study recommended, I would use CPAP mode only with Flex at 3 or EPR at 3 at all time, and set it on 10 to 13 cm max until you discuss it with your physician or clinician. My recent lab test showed 13 cm as an effective pressure but I see better results if I set it on 14 or 15 cm with 9 cm as the start. For those who can't take the hi exhale pressure some docs recommend a BiPAP machine. Dr Barry Krakow recommends for most OSA cpapers an Auto BiPAP machine and to let it pick the correct pressure depending on the changing events and body positions while you sleep.

[Emilia]

Not sure why you chose to ignore my suggestions, but you are clearly not benefiting from having your pressures wide open. Regardless of what brenda says, most folks cannot have the pressures wide open and get the response from the machine that is needed. If you follow the guidelines that the overwhelming majority of users go by, and set your pressures more tightly and within 2 above and 2 below your 90th%tile reading, you will see dramatic results for the better. Again.... use 5 to 10 and see what the results are. The choice is yours.....you can fiddle around or try what most of us have found to work.

[Pugsy]

Regarding APAP mode.
If APAP is set to 20 and there is no indication of runaway pressure to maybe try to fix leaks, then the maximum APAP setting becomes a moot point because the machine simply won't go to those higher pressures unless it feels some reason to go there.

If the maximum APAP pressure is set at 14 but never reaches 12...it doesn't matter what the maximum pressure is set at..be it 14 or 16 or 18 or 20 or even 12 because it simply is not a factor in the machine's response time if it never goes there.

Now if the machine is trying to fix leaks with higher pressure...we don't want it feeding the leak monster. That would be a reason to limit the maximum pressure.

If a person happens to be sensitive to pressure variations in APAP mode which might disturb sleep then yes, limit the pressure ranges or even switch to cpap mode.

The minimum pressure setting is the most critical setting. It needs to be close enough to needed pressure to prevent the events so that it can get to that needed pressure in a timely manner. If it takes too long to get up to needed pressure the events come and go before the pressure is at optimal level.
2 cm below 90/95% pressure would be a good minimum pressure starting point. Most APAP machines can respond quickly with just a 2 cm range to overcome.
Maximum pressure setting? Depends on what you see and what you want. If it never goes beyond 12....heck set it at 12 but setting it at 20 will give the same results unless something drives the pressure up. I would want to know if something was causing the machine to want to go much higher instead of limiting the machine with lower max. Just because a machine has an open end range doesn't automatically mean that it will use that open end range. So maximum setting often becomes a moot point.

[avi123]

Regarding APAP mode.
If APAP is set to 20 and there is no indication of runaway pressure to maybe try to fix leaks, then the maximum APAP setting becomes a moot point because the machine simply won't go to those higher pressures unless it feels some reason to go there.

If the maximum APAP pressure is set at 14 but never reaches 12...it doesn't matter what the maximum pressure is set at..be it 14 or 16 or 18 or 20 or even 12 because it simply is not a factor in the machine's response time if it never goes there.

Now if the machine is trying to fix leaks with higher pressure...we don't want it feeding the leak monster. That would be a reason to limit the maximum pressure.

If a person happens to be sensitive to pressure variations in APAP mode which might disturb sleep then yes, limit the pressure ranges or even switch to cpap mode.

The minimum pressure setting is the most critical setting. It needs to be close enough to needed pressure to prevent the events so that it can get to that needed pressure in a timely manner. If it takes too long to get up to needed pressure the events come and go before the pressure is at optimal level.
2 cm below 90/95% pressure would be a good minimum pressure starting point. Most APAP machines can respond quickly with just a 2 cm range to overcome.
Maximum pressure setting? Depends on what you see and what you want. If it never goes beyond 12....heck set it at 12 but setting it at 20 will give the same results unless something drives the pressure up. I would want to know if something was causing the machine to want to go much higher instead of limiting the machine with lower max. Just because a machine has an open end range doesn't automatically mean that it will use that open end range. So maximum setting often becomes a moot point.

Comment,

I don't have problems with leaks but if my effective pressure on CPAP is 13 cm for example and I leave my APAP at 20 cm then it will "run away" upwards if it has encountered some flow limitation or obstructives lasting 30 to 40 sec each and only slowly it will reduce the pressure afterwards if there are no more obstructives but it would be hitting central apneas or producing new central apneas, on the way down, with the hi pressure. If it encountered a central apnea first it would limit the max pressure to below 10 cm. So why should I not limit the max pressure to 14 or 15cm for example? Then it would have less of a chance to aggravate the oncoming central apneas. Other APAPs might respond differently time- wise with the rise and the fall of pressure as demonstrated in the following study:

Excerpt:

Abstract

Continuous positive airway pressure devices are routinely used to treat sleep breathing disorders. Automated devices that adjust the therapeutic pressure have recently been proposed. The utility of such devices is still controversial, as rigorous clinical comparisons are difficult to perform as a result of patient and device differences. The current authors studied automated devices in a respiratory model that was able to mimic upper airway mechanics and to interact with pressure adjustment in a closed loop. Five auto-adjusted devices were submitted to this model, in order to determine their ability to detect respiratory events and adjust pressure accordingly. All apnoeas were suppressed, whilst the reaction to repetitive hypopnoeas was dependent on the airflow shape. In some devices, repetitive hypopnoeas were changed to flow limitation. Artificial snoring caused a pressure increase in four devices, and constant mask leak was not systematically compensated. Only one device did not raise pressure in response to central apnoeas with opened upper airways. These findings show that, in some devices, event classification failed and normal airflow was not fully restored, resulting in elevated residual event indices. In conclusion, this model is useful in order to reproducibly compare diagnostic and therapeutic capacities of commercial devices as a first step, before costly clinical studies.

Source: http://www.ncbi.nlm.nih.gov/pubmed/15459146

[Pugsy]

if my effective pressure on CPAP is 13 cm for example and I leave my APAP at 20 cm then it will "run away" upwards if it has encountered some flow limitation or obstructives lasting 30 to 40 sec each and only slowly it will reduce the pressure afterwards if there are no more obstructives but it would be hitting central apneas or producing new central apneas, on the way down, with the hi pressure. If it encountered a central apnea first it would limit the max pressure to below 10 cm. So why should I not limit the max pressure to 14 or 15cm for example? Then it would have less of a chance to aggravate the oncoming central apneas. Other APAPs might respond differently time- wise with the rise and the fall of pressure as demonstrated in the following study:

What you describe happening...the pressure wanting to increase to treat obstructive event precursors and the subsequent emergent centrals as a by product, is one of the reasons that APAP with a very wide range is not the way to go. I don't know what the machine thinks when it senses a central and an obstructive event precursor within the same time frame. Which one does the machine think is the most important happening event, the central or the obstructive? I don't know. That information might be deep within the documentation on how the algorithms work.

In your situation limiting the maximum is the best way to go. You have to find a compromise between the pressure high enough to treat the obstructive components sufficiently and yet not be so high as to possibly induce centrals. Sometimes we have to compromise.

Just because a machine can go to 20 cm doesn't mean that it will. It only goes where it thinks it needs to go for some reason. Might not be the best reason but it has a reason.
If there is no reason (good or not so good) for the machine to increase the pressure it doesn't matter what the maximum is because it just won't go there. I have a BiPap and in auto mode I could set the maximum at 25 cm....I have it at 20 cm right now....I have yet to see it hit a 16 cm ceiling.

If someone has pressure induced centrals then APAP mode is probably not the best way to go anyway unless someone uses a very limited range that pretty much mimics cpap.

[Lizistired]

Too bad you didn't do your homework while you were on trial. You could have picked up a data capable Resmed machine for $300-$400.
That said, I think you need to turn off the comfort features and set your machine on cpap at 8 cmH2o for a few days and see what happens.
If you are fighting the pressure and driving it up, or having extreme leaks, your data is worthless. If you can't look at the flow graph, you don't know if they are really apneas.

[Otter]

The PR1 you had could differentiate between central and obstructive apnea. Machines without this capability are usually programmed to be extremely conservative about increasing pressure beyond a certain level, because that can cause central apnea for some people, and raising the pressure would then increase apnea instead of reducing it.

My guess, and I emphasize that it's only a guess, is that your current machine is wimping out because the programmers were afraid of causing centrals. If my guess is right, then raising your minimum pressure to a therapeutic level will bring your AHI down. Did your sleep study give you a fixed CPAP pressure?

In any case, your machine is set for much too wide a range. APAP rarely works well when used that way. The algorithms don't have strong heuristics or long memories, and hence the machines will chase back and forth across the range and often get caught too far away from your therapeutic pressure. If you can narrow the range to what you actually need, you may find that your AHI is lower than it was with the Philips.