Inverse correlation between mask leaks and AHI events

I recently brought to my doctor's attention that there seems to be an inverse correlation between masks leaks and AHI events. More specifically, I took five days with the highest AHI's and five days with the lowest AHI's and I found out that in all five sample-days the lowest leaks ( under 20 l/m) invariably yielded higher or higher -than -my-average AHI's ( 3-7 AHI's) while, conversely, the occasional highest leaks ( 30-70 l/m ) yielded AHI's within my usual low average ( less than 1.5).

The doctor found my observation very pertinent ( he qualified it as "intelligent.."). In fact he evinced from the Resmed report that, no matter my low average AHI rate, often my air ways are still obstructed more than they should and gave me a prescription to increase the CPAP air pressure from 9-15 to 12-16. He said this would take care of the occasional slight head=aches and sweating at wake-up, caused by the AHI's.

He then went on to explain that the airway obstruction creates a pressure build-inside the mask and the machine reacts by automatically evacuating the excess pressure as a mask leak.

This explains the occasional high-leaks, but not the inverse correlation. In fact I would have thought that the airway obstruction should always yield a high-leak rate. He tried to explain this over the phone, but it was getting a bit technical and we were short of time. Can anybody comment on this?

Thanks

Ittiandro

First on the high leak rate correlating with lower AHI I would suggest one possible explanation is that on ResMed machines they suppress the reporting of apnea events when the leak rate is over the redline. So you may in fact be having them while the leak rate is high, but they are not being reported. I believe you are using OSCAR. If you go into a day where you have high leak rates you can scan across and see if there are any reported events during the grayed out periods of time where the leak rate is high. I suspect you will not find any flags for events. I reviewed several days of where I had high leak rates and could not find any. Here is an example.

See the area I have zoomed in on. There is a CA event right before the high leak rate grayed out time, and two hypopnea events after, but nothing during the high leak time. This does not mean there are no events, it just means they are not being flagged. I further zoomed in on this period of time to see if I could find any events. See this further zoomed in screen shot and in particular where the green vertical cursor is located. That has all appearances of being an apnea event but was not reported.

If you go through a similar process of looking through your results during high leak times you may find something similar.

With respect to the thought that obstructive events causes mask pressure to build up and cause leaks, I have never seen that. If you look at the mask pressure trace in the screen shots I posted above there is no indication that mask pressure increases during a high leak event. Remember that your mask has a fairly large vent flow that is always venting air even when you are inhaling or exhaling or during apnea events. The fan in the machine increases and decreases in speed to maintain the mask pressure constant. There is always some fluctuation of pressure with each breath and during an apnea event this fluctuation may even decrease. There is no need for the mask to leak during an obstruction event as that is the purpose of the mask vent.

If you want to post a daily report of a typical night I could comment on the pressure issue. Ideally post one from before the pressure adjustment. Whether or not a pressure increase would be helpful depends on the types of events you are having and when during the night they occur. But if you post I would be happy to comment. When you have the screen displayed, assuming you have a PC, just press F12 and take note of where the screenshot is being saved. Then use file explorer to find the file, left click on it, and then drag it to an open post here. It will be copied into the post.

Hope that helps some,

Hi thanks for your reply and your offer to review some of my Oscar reports. I don’t know how to attach them, though. I have no IMAGE files for them, only PDF documents. If you want, I can e-mail them to you. Or you can give me instructions. In the meantime, I’d like to comment briefly on your reply, with a few questions, so that I can better understand how to read the reports . It is fascinating, but a bit challenging as I am neither a doctor, nor a technician with biomedical background ( I can read much more easily… ancient Greek than matters pertaining to medical technology ..) First off, I have compared both the Oscar and the ResMed reports . Indeed, that inverse correlation holds for both. You were right, there are no AHI’s in the report for the hourly time windows of the large leaks. Why so ? How reliable then are these reports if they miss some AHI’s? . Let me say, though, that I find it difficult to understand why both Oscar and ResMed should exclude from the count the AHI’s occurring when the leaks are large. Why should these AHI’s be of a lesser value in the overall clinical appraisal of the report, to the point of ignoring them? In fact, I find it a bit intriguing that my doctor would want to increase the pressure setting in spite of the very low AHI readings. I simply told him that occasionally I still wake up in a light sweat and a slight head ache. So he must have sniffed something else, in spite of the very low number of AHI’s. … May be I misunderstood the explanation he gave me, which you yourself question, but my doctors’ explanation went at least some way to explain the correlation, rather than simply saying that both Resmed or Oscar have deliberately designed the reports to ignore AHI’s when the leaks are large. If so, the question is, again, why? Perhaps there is a scientific explanation.... Secondly, why do you say that in the 2nd report with large leaks that you zoomed on there must be some AHI’s that are not shown?
Thirdly, I assume that perhaps the duration of the AHI’s is more important than their number, but where is the duration of each AHI occurrence ( or the total duration) shown? Lastly, in my reports which you will hopefully receive, the mask pressure graphic shows as “plots disabled “ Why ?

You may want to have a look at these issues. I’d really appreciate.

Thanks

Franco V.

Thanks I am on PC, Windows 10 32-bits. Here are some more points.

1.The term AHI is, from what I understand, an umbrella term including a variety of apnea events, like O.A, Hypoapnea, Central Apnea and others. To be able to identify them individually is essential, but if Resmed, to this purpose, removes the AHI’s from the report in case of large leaks, will these individual apnea modes be still traceable? If not, won’t the reports be unreliable, if they don’t show the correct number of AHI events?. It is a bit like deleting a folder from the computer: all the files it contains will also be gone.

1. Your comments have been invaluable, also because they have led me to look into the differences between the various apnea events, like Central Apnea, Obstructive Apnea, Hypoapnea, etc.
   I don’t have, though, a clear appreciation of their impact on the patient’s sleep quality and, ultimately, on his/her health. .

I’d would think that OA has perhaps the greatest impact, but perhaps other apneas are just as important..

My AHI’s have drastically gone down, in the average, to well under 2 /day over one year. . Sometimes there is none and sometimes, very rarely, they spike to 6-8 in one night. Looking at my reports, I found that the OA’s represent about half of my AHI’s. and this raises a few questions.

Of course, if the AHI’s for the night are down to one or less, the OA component becomes insignificant. When, however, the AHI’s are six or eight and half of them are OA’s, I wonder if there isn’t a more serious impact on health.

The report of 12/22 , which I will attach as soon as I know how to do it, shows for example 8.47 AHI’s, of which 7.02 ( practically 90%) are OA’s. Considering the TTIA for the night ( about 20:min), each OA had a duration of 2.85 min. A lot! . Of course, I didn’t stop breathing foe almost 3 min, or I’d be dead, but 20 min. of OA’s events shouldn’t perhaps be underestimated. This may be why my doctor has decided to increase the pressure.

3.I’d also like to have your take about the possible connection between sleep apnea and cardiac arrythmias. Can sleep apnea cause arrythmias?. Two years ago, before being treated for Sleep Apnea, I had an episode of Afib, when I was about to begin my usual 6 km running session . I am 79 and it was the 1st time. The cardiologist put me on betablocker ( Metaprolol) as a precaution, but I had a 2nd episode a few days ago, with the pulse briefly shooting up to 160 bpm, with absolutely no discomfort, though.
I spoke to the doctor again. In the meantime my heart had gone back to normal, except that I have a lingering arrhythmia, with the pulse fluctuating between 90-110 bpm ( it usually is 60 bpm at rest ) , It doesn’t go away. I don’t even feel it and I can detect it only with the cardio watch, but it is still there. If it it doesn’t go away, I’ll speak to my doctor again, but I wonder if arrythmias are an expected… byproduct of Sleep Apnea.

Thanks for your input, as usual

Ittiandro

Thanks so much I think the most interesting reports to look at are those showing an unusual high number of AHI’s ( up to 8) and consisting of a majority of OA’s ( up to 90%) or a 50/50 mix of OA’s. and CA's. Given the TTIA and the relatively high number of OA’s and CA's making up the mix, I believe that in the long run there is less oxygen going into my system at night and this may have some effects, like arrhythmias or other .. I’ll send you the report as soon as I have sorted out the nuts and bolts of how and what to post. Getting there. Please bear with me…

1. The F-12 screenshot only shows a section of the report at a time and there are a lot of graphs, more than one page. . I suppose not all of them are relevant to you. Which graphics should I include and how do I extricate them from the page to drag them into my post?
2. I suppose I don’t have to include the summary section to the left, do I?
3. In your previous reply you included two segments of the graphs, not the entire graph bar. Do I have to include the complete bar for each graph. ? I suppose so

The mask pressure has been increased by the technician ( 12-16) according to the doctor's prescription, effective tonight. I'll see. I hope it won't feel like snow blower into my throat. I had enough of snow and ..snowblowers here in Montreal.!. .

Thanks

Ittiandro

Here is one report. I was unable to include the leak rate graphic. I hope it won't matter. There is also a 2n one with a different mix that I'd like to send, but it won't go through on the same post.

Thanks

Ittiandro

Here is the 2nd one

Thanks

Franco

Hello Sierra

HI Thanks for your comments and explanations. I am sending a couple more daily reports after the pressure change to 12-16. Those I have previously sent are perhaps not as representative, because they are way off my average in terms of AHI. I sent them in case you see something standing out.

It is the first time that my AHI’s keep under ONE for two consecutive days. May be it is a sign of improvement. Regarding the “pressure plots disabled”, I have now restored the setting to default as per your instructions. I have also upgraded to Oscar 1.2.

I am unable to turn off the EPR, though. This option does not seem to be included in the Preferences, but I prefer not to play with this setting. I’ll just wait to see if there is any improvement after increasing the pressure.

I have also checked the CSR issue. The Stats show an incidence of 0% over the last 30 days and 0.11% over the last 6 months. I don’t think I should worry. From what I begin to understand, there may be some interesting clues in the Flow rate, the Flow limit and the Minute Ventilation graphics, but all this is kind of nebulous for me at this stage, because the analysis of these parameters involves a good understanding of technical and physiological issues. It is really a fascinating issue, even more so that it is about my health and I hold dearly to it.

Here are the reports

Thanks again

Franco

HI Thanks for your comments and explanations. I am sending a couple more daily reports after the pressure change to 12-16. Those I have previously sent are perhaps not as representative, because they are way off my average in terms of AHI. I sent them in case you see something standing out. It is the first time that my AHI’s keep under ONE for two consecutive days. May be it is a sign of improvement. Regarding the “pressure plots disabled”, I have now restored the setting to default as per your instructions. I have also upgraded to Oscar 1.2. I am unable to turn off the EPR, though. This option does not seem to be included in the Preferences, but I prefer not to play with this setting. I’ll just wait to see if there is any improvement after increasing the pressure. I have also checked the CSR issue. The Stats show an incidence of 0% over the last 30 days and 0.11% over the last 6 months. I don’t think I should worry. From what I begin to understand, there may be some interesting clues in the Flow rate, the Flow limit and the Minute Ventilation graphics, but all this is kind of nebulous for me at this stage, because the analysis of these parameters involves a good understanding of technical and physiological issues. It is really a fascinating issue, even more so that it is about my health and I hold dearly to it.

Here are the reports

Thanks

Franco

HI Thanks for your comments and explanations. I am sending a couple more daily reports after the pressure change to 12-16. Those I have previously sent are perhaps not as representative, because they are way off my average in terms of AHI. I sent them in case you see something standing out. It is the first time that my AHI’s keep under ONE for two consecutive days. May be it is a sign of improvement. Regarding the “pressure plots disabled”, I have now restored the setting to default as per your instructions. I have also upgraded to Oscar 1.2. I am unable to turn off the EPR, though. This option does not seem to be included in the Preferences, but I prefer not to play with this setting. I’ll just wait to see if there is any improvement after increasing the pressure. I have also checked the CSR issue. The Stats show an incidence of 0% over the last 30 days and 0.11% over the last 6 months. I don’t think I should worry. From what I begin to understand, there may be some interesting clues in the Flow rate, the Flow limit and the Minute Ventilation graphics, but all this is kind of nebulous for me at this stage, because the analysis of these parameters involves a good understanding of technical and physiological issues. It is really a fascinating issue, even more so that it is about my health and I hold dearly to it.

Here are the reports

Thanks

Franco

HI Thanks for your comments and explanations. I am sending a couple more daily reports after the pressure change to 12-16. Those I have previously sent are perhaps not as representative, because they are way off my average in terms of AHI. I sent them in case you see something standing out. It is the first time that my AHI’s keep under ONE for two consecutive days. May be it is a sign of improvement. Regarding the “pressure plots disabled”, I have now restored the setting to default as per your instructions. I have also upgraded to Oscar 1.2. I am unable to turn off the EPR, though. This option does not seem to be included in the Preferences, but I prefer not to play with this setting. I’ll just wait to see if there is any improvement after increasing the pressure. I have also checked the CSR issue. The Stats show an incidence of 0% over the last 30 days and 0.11% over the last 6 months. I don’t think I should worry. From what I begin to understand, there may be some interesting clues in the Flow rate, the Flow limit and the Minute Ventilation graphics, but all this is kind of nebulous for me at this stage, because the analysis of these parameters involves a good understanding of technical and physiological issues. It is really a fascinating issue, even more so that it is about my health and I hold dearly to it.

Here are the reports. The 2nd one won't go through o. Thanksn the same post. I'll send it separately

Hi Sierra I am sending a couple more daily reports after the pressure change to 12-16.
It is the first time that my AHI’s keep under ONE for three consecutive days. May be it is a sign of improvement. I have now fixed the “plots disabled” issue as per your instructions. I have also upgraded to Oscar 1.2. Regarding the CSR issue, the Stats show an incidence of 0% over the last 30 days and 0.11% over the last 6 months. I don’t think I should worry. From what I begin to understand, there may be some interesting clues in the Flow rate, the Flow limit and the Minute Ventilation graphics, but all this is kind of nebulous for me at this stage, because the analysis of these parameters involves a good understanding of technical and physiological issues. It is really a fascinating issue, even more so that it is about my health and I hold dearly to it.

Here are the reports

I'll send a 2nd and last report on a separate post. I have been trying for two days, but

Thanks

Ittiandro

Sierra As per previous post, here here is the 2nd and last report after the pressure increase. Over three days of increased pressure , even though there still is a mix of OA and H's, the AHI's seem to have fallen consistently below 1

Thanks again

Hi Sierra Regarding the EPR change I am not too keen on changing the original settings prescribed by the doctor. However, if you tell me how to do it, I’ll try it just to see how it works. I can always reset it later.

Except for the very few 0 (zero) AHI’s I have got so far,( probably three or four in a year), my AHI’s are getting consistently lower and lower after the pressure change. Today, the 3rd day, the AHI's were 0.29, all of which being Hypoapneas . No OA’s or other

I also noticed a drastic change in the Minute Ventilation graphic: the waveform is considerably smoother when there are few or no OA’s. Conversely, the more the OA’s, the more does the Minute Ventilation wave pattern look like…. a seismograph during an earthquake and vice versa.

This can easily be seen by comparing my recent graphs with the older, high AHI’s ones, especially the one of Dec 16 which I had sent you. I seem to detect changes also on the Flow Limit graph , but I cannot put my hands on them. All in all, I am very satisfied with my therapy, if it continues like this.

If you have any comments, I always like to hear them..

Thanks

Ittiandro

I will start a new full width post because when you keep replying to post after post they get kind of narrow on the page! You said:

"Given the fact that with the increased pressure my AHI's are so dramatically low, with practically no OA's and very few, short Hypoapneas, what perceived benefits should I expect from using the Ramp-only feature? Better, more refreshed?"

I can't predict how refreshed you will feel, but what you quite likely will see is that the actual pressure used in auto over the night will go down. This should feel more comfortable, and make the mask less likely to leak. That also could make you feel more comfortable. I wouldn't expect your AHI or apnea events to get better or worse.

On the travel issue, before COVID, we travelled a lot. Airlines let you take a CPAP as an extra carry on piece of luggage with no charge. They will want you to take the CPAP out of the case, but other than that you should sail through security. Getting water for the humidifier can be an issue. For periods of up to two weeks we just use tap water. You probably have to use some extra vinegar to clean out the reservoir after you get back, but overall no harm done. If you look around the airport in the boarding lounge you may be surprised how many people have a CPAP. The advantage of the AirSense 10 is that it packs up quite small. It can accept 230 volts or 110, but you may need an adaptor to fit the wall socket depending on the country. We would not consider travelling without them. My wife and I both use a CPAP.

I am sending last night’s report, after the EPR setting change. The AHI’s have slightly increased, with Hypoapnea and RERA component, no OA’s. . Actually this time my sleep was a bit disturbed by frequent leaks throughout the night, with a persistent ( and bothering) hissing sound. Usually, I can fix this by readjusting the straps and the mask position which sometimes goes off center when I change side. Not this time. May be the silicon seal needs to be replaced. I don’t know if the EPR new setting has something to do with this. I’ll see how it goes tonight. Regarding traveling , I was wondering if it is safe to go without it. I wouldn't see why not, because I have traveled all my life without trhe CPAP, but may be with age my physiology has changed and it will affect me . Thanks

Franco

Hi Sierra With the EPR still off, last night was very smooth. The only thing I noticed was an unusual very low pulse at wake up. Usually it is 60 bpm because I take a betablocker following an isolated episode of atrial fibrillation almost three years ago, but this time It felt even lower. It was also skipping a beat, although very regularly. I don’t know if it is related to the EPR setting and the oxygenation pattern. I don’t worry, anyway. For one thing, I am not new to arrythmias. I had a very unusual one recently, with the pulse shooting up and down between 90-130 bpm, accasionally 150 bpm, for about a week, with absolutely no symptoms. I rushed to the emergency, but the ECG indicated a perfectly normal heart. The doctor said I shouldn’t worry about occasional arrythmias or tachycardias as long as I have no symptoms, like chest pains, fatigue or breathing difficulties. She said the cardio watch is not a medical instrument. It doesn’t show the complete wave pattern It only picks up the irregular beats and it averages them out in a way that can be misleading. You can have a look at the report

Thanks, as usual.

Yes, I might as well switch back to Full time as there isn't much of a perceived difference in having the EPR set at Ramp only. What I understand less, though is the Flow limitation issue and what it means to have the Flow limitation number doubled, along with the doubled pressure and the implications

Thanks

Franco

Franco, your good results using EPR motivated me to try it again for myself. I went through a very long trial and error process to end up with what I have been using for a couple of years now -- 11 cm fixed pressure in manual CPAP mode with EPR on Ramp Only. For last night I changed that to 13 cm (to compensate some for the EPR reduction) and turned EPR back to full time. I had intended to try this a long time ago but had never gotten around to it after I settled on the fixed pressure mode. Your results prompted me to try it.

In any case I got about the best results I have ever had with this change -- API of 0.4. 95% Flow Limitation was 0.01. Almost zero. This is one night only and may have been a fluke, but I will leave it there to see. My biggest issue has been hypopnea events and not so much OA events. For the night I got zero hypopnea events and one each of the CA and OA. Kind of amazing. Will have to see if it is repeatable. I did not notice the extra pressure during sleep and my leak rate was quite acceptable, although not zero.