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High AHI readings - no explanation from somnographer
Hi all

I'm 51 years old, diagnosed 5 years ago with OSA and 4 years ago with Chronic Fatigue Syndrome. I'm overweight ( 6'0" and 118kg/260lb/18.5st). As per profile, I'm using ResMed S9 Autoset with H5i humidifier and climate control hose, Swift FX nasal pillows, and 10-20 cmH2O variable pressure.

I've been having success with the machine, which I bought after the initial sleep lab/diagnosis, (overnight AHI typically 3.0 or less, even 0.0 occasionally) until 2-3 months ago when readings started getting very high. For example last night's reading was:

Used Hours: 8.0; Pressure: 13.0; Leak: 8L/min
AHI: 48.4; Total AI: 47.8; Central AI: 46.2.

I woke up unrefreshed and with a headache, unlike the night before where my AHI was 4.4. These high readings always include a high Central AI figure (typically just 2-3 less than the AHI number).

I've spoken to the sleep technician at my nearest Sleep Lab. She tells me that APAP is a waste of time and doesn't work, that the machine can't possibly correctly detect central vs obstructive apnoea, and that I should ignore these readings as clearly wrong, since if they were accurate I'd be dead.

I'm not inclined to believe her even though she has a certification (not sure what exactly).

How worried should I be? Is it possible that this is related to something else such as sleeping position, mouthbreathing or the like, and that the machine is actually presenting false readings?

Thanks for any advice
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Hi Jona.  Welcome to the Apnea Board.  You are going to need to download and install the Sleepyhead software so that you and we can get a handle on what is going on with your therapy.  There are links in my signature that you can use to get started with Sleepyhead.  The machine does have an algorithm that sends out low frequency pulses of air that can detect if your airway is open when your respiration has stopped.  You can also focus in on 2 to 3 minute clips of your breathing to recognize the waveforms associated with different types of Apnea.  That said, there are several things that can cause an increase in Centrals such as you have seen.  One thing in particular is a change in cardiac function.  Along with looking at your respiration and machine functions you most likely need to visit with a Cardiologist to address the possibility that your Centrals are a response to a treatable condition called CHF (congestive heart failure).  Stick with us here and we will help walk you through this.  

Apnea Board Member RobySue has posted a Beginners Guide to Sleepyhead Software here:  http://www.apneaboard.com/wiki/index.php...SleepyHead

Download Sleepyhead
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Sleepyhead graphs would tell a great deal about what's going on. The stats you present don't tell if the pressure of 13 is mean, 95th percentile or maximum. Sleepyhead will tell.

First, do you have EPR on? If so, what level? Reducing or turning off EPR may prevent CO2 washout which may cause CAs.

It's possible that the CAs are pressure induced.
You may be able to tame them with a lower pressure; and it might be a balancing act between OAs and CAs.

You shouldn't be worried; this can be addressed. The RT's remark that "...if they were accurate I'd be dead" is not helpful. The entire remark shows that the RT has limited understanding.

Note the machine that richb has. You may have to step up to an ASV machine which is the premier machine for addressing "mixed" apnea.

It's possible that you may be able to fine tune your setup to get consistent, acceptable therapy. The Autoset is perhaps the most widely used machine. While it may not be as good as polysomnography at differentiating CA from OA, it's darn good.

When the wizard of Murrysville gets on the forum, he'll set you on a good path. (I'm having a bit of fun there. Member Sleeprider is one of the forums most helpful members.)

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JustMongo passed away in August 2017
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Thanks for your quick reply. Unfortunately installing software might be a painful process, since the operating system I use is FreeBSD....

I realise I'm asking for a response based on relatively little information but the essential question is which of three paths should I follow here?

1. Trust the sleep technician and ignore the readings;

2. Follow up but without being too worried (sleep lab is fully booked until April);

3. Follow up urgently as persistent AHI readings of high 20s - mid 40s after 5 years of readings in low single figures suggest an underlying serious medical issue.

I appreciate the advice to consult a cardiologist. I can have an ECG at my family doctor's practice and get a referral as needed.

Thanks again
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Hi justMongo

Sorry was replying to RichB when your answer came in.

I have EPR set to 3. I don't know which pressure level ResMed S9 reports - the readings are from the detailed menu which is only accessible with a long double-button-press, if that helps.

My health worry is that I haven't changed any of the settings, and I have replaced the filter, mask and hose on schedule; but after 4 years of successful therapy on the same settings, I'm suddenly getting these extremely high readings most nights, with nothing obvious having changed. I don't think it's a calibration issue as I still get scores of 4-5 once or twice a week and 15-20 sometimes.
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A question for you: Do you sleep on your side? Some back sleeping individuals may reduce their apneas if they change to sleeping on the side. A bolstering pillow may help prevent rolling onto your back.
Please organize your SleeyHead screenshots like this.
I'm an epidemiologist, not a medical provider. 
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I generally sleep on my side. My partner has noticed that my breathing is much worse (they says that I don't exhale until I have a shuddering release of breath) when on my right side, and generally easier when on my left side.

I have woken up flat on my back a few times recently - I've been getting knee and hip joint and leg muscular pain at night and I think I move to relieve that.
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Jona, your recent result are suggesting predominately central AHI. This has come up from a historic efficacy of normal AHI less than 3, to your current event rate of 46. I think your technician is giving you bad advise, and the correct response on his part is to suggest getting a referral so he can measure your events to verify or disprove them using his much more accurate instrumentation.

The advent of central apnea can be significant, and have a number of different sources. As mentioned by others, it would be extremely helpful to look at the events on a SleepyHead graph, where we could also look for patterns of periodic breathing, event duration and other important details. Since you are using a fixed pressure of 13, the correct response to centrals is to reduce pressure and/or reduce EPR. You might start reducing pressure by 1-cm, and eliminating EPR (exhale pressure relief) which can cause CA in some people.

The other concern is that you have experienced a change in your health. CA events at this rate can be related to heart failure and some other conditions. You may want to check this out. I still think finding a way to buy or borrow a PC that can fill in where your FreeBSD machine is unable to help is not an unreasonable investment. Check Craigslist, or consider a separate small Windows partition.
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Change in health is what I'm concerned about. My pressure setting is actually auto with min 10, max 20. 13 is what the machine reported as a nightly value - not sure if that's average or 95th centile. The "score" change has come without any settings or lifestyle changes.
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G'day Jona, welcome to Apnea Board.

I concur with the responses above - you should see your GP and rule out any serious conditions such as congestive heart failure or other cardio-pulmonary conditions. Because central apnea is a central nervous system condition, perhaps a neurological screen would also be a good idea.

The second thing you should do is find yourself another sleep technician - the one you have is giving you extremely bad advice. When you do get another tech, get your machine checked out, just to make sure it's not playing up. It's possible (but I think unlikely) that a failed sensor may be responsible for mis-reporting your results. As also mentioned above, SleepyHead flow charts will give a pretty good indication in this regard. I think you should consider getting hold of a Windows or Mac computer to run SleepyHead, even if just for a while.

You mention there have been no lifestyle changes, so can we rule out any medicines or drugs (especially opioid painkillers and things of that nature) which may cause central apnea?

Finally, follow SleepRider's advice in relation to pressure and EPR - it may be sufficient to give you some relief.
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