Please explain I:E ratio

[yankees123]

I have seen many threads concerning looking at the I:E ratio that sleepyhead reports.  
Can someone please try and explain what is meant and what a good or bad ratio is and what it actually means.  
If an example from a screenshot is possible to explain it would be appreciated.  Also from reading the threads it seems that by making certain changes example either increasing or decreasing pressure or epr gives a more proper ratio which in turn gives a more favorable situation.

Thanks

[mesenteria]

I don't think it's a ratio so much as the wearer's personal index of comfort and continuity of use...IOW, how successful the therapy is ultimately.  Some people need more pressure relief during exhalation than others.  So, the machines permit some pressure relief, I believe with RESMED's latest machines providing up to 3 cm h20.

[Sleeprider]

I wrote this section of the Beginner's Guide to Sleepyhead to address this question, and perhaps it should be in a separate wiki. http://www.apneaboard.com/wiki/index.php...ailed_look The detailed I:E graph in that example came from a member that was getting an inverse I:E ratio reported in error. As you can see, the I is equal or less than E.

Let's be clear about the I:E ratio, the machines miscalculate it all the time. Sleepyhead even has math errors for certain machines. Normal I:E ratio is for inspiration to be equal or shorter in time to expiration. If a person has a respiration rate of 12 breaths per minute, that is five seconds for each breath cycle. A correct expression of I:E ratio would be 1:1 if both I and E were 2.5-seconds each. If inspiration was 2 seconds and expiration was 3 seconds the I:E ratio would be 0.66:1 which is normal. An inverse ratio is anything greater than 1.0 where inspiration is longer than expiration. and inhale of 3 seconds and expiration of 2 seconds is 1.5:1.

We often see Sleepyhead charts where the inspiration time is much longer than expiration. This may be an indication of a respiratory problem, such as resistance or flow limitation during inspiration, or more often it may just be machine error. I have to physically look at the flow chart close-up to know for sure. Philips machines seem to be more vulnerable to making this error, and it is important because of the way CFlex and AFlex affects the user's respiratory timing. Anyway, there is a strong possibility that when we see an inverse I:E ratio, that the event rate will be higher. This has lead me to the opinion the Philips machines sometimes transition from "EPAP" to CPAP pressure before the user's spontaneous respirator effort, and this may ultimately suppress volume resulting in hypopnea or flow limits. This may be why we see some users with much higher event rates on Philips machines that seem to immediately have better results with a Resmed. Please note, this lower efficacy with Philips using Flex is not based on research or anything other than casual observation of many users and my opinion.

[yankees123]

Thanks so much SR for your detailed explanation.  
I have posted a screenshot from yesterday so you can look at my flow chart and also give me a feedback concerning the ratio.  The flow chart seems a little "funny looking" as far as the inspiration trace followed by the expiration trace.  
Your input is much appreciated. BTW the 95% flow limitation shows 0.05 which for me is very low thanks to all your guidance.

[Sleeprider]

Actually looks pretty good. We can't see the I:E ratio at anything farther out than a 2-minute segment where the individual wave-form is easily seen on the time-line. You can just take a 15 second interval and count the breaths, then multiply by 4 to get BPM. I see you have a zero-line in there and the breaths are lining up on it well, so just sample the inspiration time and expiration time and see what you get visibly from the time it goes below zero to when it rises above (expiration time) and the time it goes above zero to when it returns to zero (inspiration time).

[yankees123]

As always thanks for your expertise SR will do.

[AshSF]

Thanks SR for the detailed analysis of PR’s IE ratio calc.

When I eyeball the flow rate graph on SH for my PRS1 and my Dreamstation Auto, I get the feeling that SH calculates this ratio by dividing inspiration wave time (when waveform rises above zero and falls back to zero almost like a sincewave), with expiration wave time (when waveform goes belo zero and comes back nearly to zero typically in a sawtooth shape). but doesn’t take into account the time when the flow rate is almost zero (from when waveform is almost zero after exhale, to when inspiration starts again).

[Sleeprider]

Thanks SR for the detailed analysis of PR’s IE ratio calc.

When I eyeball the flow rate graph on SH for my PRS1 and my Dreamstation Auto, I get the feeling that SH calculates this ratio by dividing inspiration wave time (when waveform rises above zero and falls back to zero almost like a sincewave), with expiration wave time (when waveform goes belo zero and comes back nearly to zero typically in a sawtooth shape). but doesn’t take into account the time when the flow rate is almost zero (from when waveform is almost zero after exhale, to when inspiration starts again).

Exactly, but Sleepyhead does not actually calculate the inspiration and expiration times, but is instead reporting the machine data.  Sleepyhead does perform a calculation from that data to report the I:E ratio, and that output has had errors. The machines frequently under-report the expiration time and include much of the null flow as inspiration. This error is much more apparent in people with a rapid expiration and long zero-flow, than with those that transition more smoothly from exhale to inhale without a sustained near zero flow.

[Regular Joe]

Sleeprider, I found the section you wrote of the Beginner's Guide to Sleepyhead to be very informative.  I've been on CPAP and on here for six years.  I've been using SH from the start and I never recall seeing this information before.  Thanks for taking the time to write and post it.  I thought I knew everything, but I just learned a lot.