Why data discrepancy?

[xdc]

I had a home sleep study using a Nihon Kohden 5-channel EOS Recorder. The report I received from my sleep doctor showed a total of 81 Obstructive Apneas and 132 Hypopneas. Total recording time was 8.6 hours = AHI of 24.7. I believe I only actually slept a total of 3 hours that night. I was started on APAP on March 18, 2011. I've been 100% compliant and don't really feel any difference in my symptoms of day time sleepiness, fatigue and waking several time at night. I have Encore Pro software that shows 0.0 obstructive apneas from the first night. Typically it shows lots of Clear Airway Apneas in the second half of the night and several hypopneas scattered throgout with periodic breathing about 2% of the night. Average AHI is around 8. Yesterday I procured a copy of the orginial sleep study data. It showed quite different numbers than what my sleep doctor gave me, i.e., Total Obstructive Apneas = 9, Total Hypopneas = 46. Desaturation <100% = 90, Desaturation <90% = 5. SaO2 Nadir: 88% with AHI = only 6.39.
Does anyone have an idea why the data is so different? Also any thought about the above greatly appreciated.
I'm using a Respironics Remstar Auto A-Flex with System One Humidifier. Minimum Pressure set to 7.0 Max 20. 90% average pressure is around 8 to 9. Using the new Respironics Golife nasal pillows that I really like and have no significant leaks.

Aloha

[JDS74]

Have you kept a log of the times you wake up at night? (assuming it still happens while using your CPAP )
You may be able to correlate the apnea events on your reports with your actual arousals.

An AHI in the range of 8 - 12 for me and I feel fairly bad the next day. Below 5 and I feel pretty good. Those numbers are quite individual specific - some members who post here don't feel good until they are well below 2.

I'd have a conversation with your sleep doc to get an explanation of the data discrepancies - those numbers are quite different. If you want to do the self-titration, you might consider including that in your sleep doc discussion.

I started out with a pressure range like yours ( 5 - 20 ) but find that I did much better when I self-titrated and eventually got down to a range of 10 to 13.5. The occasional times when my machine peaks out instead of getting to higher pressure don't seem to cause any problems. I began incrementing the EPAP value in steps of 0.5 cmH2O while watching the CSA's. I took two to three days at each new EPAP level to get an idea of what the reaction would be before moving to the next higher pressure.

I lowered the IPAP max because of a defect in my machine that occasionally would drive the pressure straight to the IPAP max and keep it there for the rest of the night or until I woke up and turned the machine off. Philips replaced the machine but I left the IPAP max down at 13.5 'cause it seems to work for me. Had a nice chat with my sleep doc this week and he was delighted with my new AHI numbers and suggested I continue the titration as long as I could see improvement.

[AMUW]

1. I had a home sleep study using a Nihon Kohden 5-channel EOS Recorder. The report I received from my sleep doctor showed a total of 81 Obstructive Apneas and 132 Hypopneas. Total recording time was 8.6 hours = AHI of 24.7. I believe I only actually slept a total of 3 hours that night...
2. Yesterday I procured a copy of the original sleep study data. It showed quite different numbers than what my sleep doctor gave me, i.e., Total Obstructive Apneas = 9, Total Hypopneas = 46. Desaturation <100% = 90, Desaturation <90% = 5. SaO2 Nadir: 88% with AHI = only 6.39

I for one can attest to 50% difference between two off-CPAP pulse oximetry and RDI results performed at 2 different times with different equipment, different sleep position, and different sleep comfort conditions.

If you mean that 1. and 2. above are the same sleep study
... (and the same patient's name appeared on both ),
then a possible explanation may be the initial computer-scored data report vs. the later tech-reprocessed report:
- in my case AHI was defined as (apneas + hypopneas) / (total SLEEP time) not RECORDING time
- the sleep technician may have chosen to reprocess the raw data with a different protocol: count only the events during actual sleep stages ... and consider the other events as artifacts, not representative of arousals interrupting your normal sleep condition
- did your oxymetry data also include the duration of desaturations and an Oxygen Saturation Index?
- forgive the naive question, but are you maybe talking about a split-night study?
- for additional meaning, your report should also have statistics of sleep duration in each stage, and histogram showing your body positions and providing a rough impression of sleep fragmentation

With this additional information, does the math turn out OK? What degree of OSA severity did the sleep doctor assign in the end? an AHI of 24.7 is quite a different ball game from 6.39 for your health as well as for your insurance.

[billbolton]

Does anyone have an idea why the data is so different?

The obvious answer is that the data scored by your xPAP machine is while you are under treatment for OSA, which the data in the sleep study was while you were not.

The other thing to keep in mind is that your xPAP machine has a single "channel" of data to work with (the air flow), while the home sleep study device had 5 "channels" of data to work with, in determining the nature of any SDB event.

Cheers,

Bill

[xdc]

Thank you to everyone who responded, I really appreciate it. To AMUW: This was a home sleep study with no EEG leads, so I'm not sure how the tech or whomever scored my test knew when I was asleep or not, perhaps from the breathing pattern. The initial report form the DME was computer scored. Regarding Desaturation length, what the computer scored report shows = Obstructive Apneas Average length 15.0seconds, Maximum 30.7 seconds. Obstructive Hypopneas Average length 30.3 seconds, Maximum Length 58.2 seconds. What I see on the data generated by my APAP machine on the Encore Pro Software is just about the same every night. I fall asleep with no trouble and during that first 3 to 4 hours there are practically no events at all. I inevitably wake up after 3 or 4 hours then after going to bathroom strugle to fall back asleep and I think I spend lots of time in the transition between wakefullness and early stages of sleep and that is where most my hypopneas and clear airway apneas happen. I understand that this might be a normal occurance in that transition sleep stage. Problem is I probably spend several hours in that state. And yes, 1 and 2 are the same sleep study. The sleep doctor said I had "moderate/severe obstructive apnea." Since the first day of using APAP it shows zero obstructive apneas. I don't think that the 5 channel home sleep machine even registers central apneas.
To JDS74: Thank you for the info on home titration. Increasing from 5 to 7 did seem to help and since currently average cpap pressure is around 7.5 and 90% pressure is around 8.5 I think I will try upping it like you suggested.
To billbolton: It isn't the difference between the initial sleep study and my APAP machine generated data that concerns me, obviously they should be different. What I was questioning was the difference in the numbers that my sleep doctor gave me and the scores on the actual test data for the exact same study.

[AMUW]

To AMUW: This was a home sleep study with no EEG leads, so I'm not sure how the tech or whomever scored my test knew when I was asleep or not, perhaps from the breathing pattern.

Sorry about misunderstanding your home equipment's 5 channels... was just trying to help, but using insufficient information. Apparently you were fishing for somebody with the same equipment.
I now see at http://www.nkusa.com/neurology_cardiolo ... ochure.pdf a device; no EOS designation, but with ~ 5 sensors.
My home off-CPAP test used only 3 channels: nasal cannulae and pulse oxymetry. One source of trouble I wasn't told of: every start button on-off, like when going to the bathroom, starts a new recording session.
Another observation: whether you're awake or asleep can also be estimated from the respiratory cycles; in my case falling asleep reduces the flow amplitude to 50% and increases the frequency two-fold. So the sleep tech may have truncated out the no-sleep time periods.
I too would be puzzled if the sleep doctor used the computer-generated severity index of AHI = 24.7 and declared me medium / severe OSA ... then the tech re-evaluation of the first test, or a second test, came back with a much lower AHI value. Sounds like somebody owes you an explanation.

Now to the on-CPAP part of your question; if I understand correctly
- you seem to be happy with the lower on-CPAP event count
- but unhappy with your unimproved subjective feeling of sleep quality;
to which my similar experience may sugest that just reducing the duration of the events may improve the 10 sec apnea count and the oxygen desats, but not improve the sleep fragmentation ... at least not yet.