Experiments on RemStar Snore Detection...

derek · Post by **derek** » Sat Feb 19, 2005 7:00 pm

I have been puzzled by what Respironics defined as a "snore" when reporting the Snore Index (SI) in Encore Pro. So between chores today I did a set of simple experiments to find out what was going on. For each experiment I defined a new patient in Encore Pro, put on the mask made a bunch of "snores" or pseudo-snores, then downloaded the data and used the indicated SI and session duration to find the total number of snores that Encore Pro thought it had detected.

In each experiment the APAP pressure started at 5.5 cm H2O. I also recorded the pressure at the end of the experiment to determine the effect of the "snores" on the therapy.

Here are some results:
Experiment 1: Regular snores (one per inhalation): I snored once per breath, for five breaths each minute, for six minutes - giving a total of 30 snores. Encore Pro reported:
Snore Index: 282.9
Duration: 7 mins
APAP pressure at end of experiment: 10.5 cm H2O
Total recorded snores = 282.9x7/60 = 33 snores
Conclusion: Encore Pro slightly over-counted the snores. This activity had a strong effect on the APAP pressure, raising it from 5.5 cm to 10.5 cm

Experiment 2: Short snores (within a single breath). This time I made 5 short snores (snorts) within a single breath, once per minute for six minutes. Total of 30 snorts. I was attempting to determine if the overcounting above may have been caused by interupted snores. Encore Pro detected:
Snore Index: 85.7
Duration: 7 mins
APAP pressure at end of experiment: 7.0 cm H2O
Total recorded snores = 85.7x7/60 = 10 snores
Conclusion: There were 6 groups of 5 snores. Encore Pro overestimated the groups, but did not count all of the short snores. A few times it counted more than a single snore within the breath. This experiment had a slight effect on the APAP pressure.

Experiment 3: Coughing. I wanted to see if a cough might be interpreted as a snore. I coughed once every ten breaths for a total of 20 coughs. Encore Pro reported:
Snore Index: 20
Duration: 9 mins
APAP pressure at end of experiment: 6.5 cm H2O
Total recorded snores: 20x9/60= 3 snores
Conclusion: Coughs are generally not interpreted as snores, and coughing does not significantly affect APAP pressure.

Experiment 4: Talking with the mask on. I wondered if the acoustic energy from the vocal chords would propagate down the hose and trigger the snore detection. Every ten breaths I said very loudly "I love APAP" (now you know how crazy I am ), for a total of 20 times. Encore Pro reported:
Snore Index: 5.2
Duration: 12 mins
APAP pressure at end of experiment: 5.5 cm H2O
Total recorded snores: 5.2x12/60 = 1 snore
Conclusion: Talking does not significantly affect the snore index, and does not affect the APAP pressure.

Experiment 5: Rubbing the hose on a sharp hard surface. I wanted to see if dragging the hose across an edge on furniture might generate sounds that would be interpreted as a snore. Every ten breaths, on inhalation, I took a wooden ruler and dragged it across the corrugations of the hose for a distance of about 9 inches, causing a sound that was somewhat snore like. I did this a total of 20 times. Encore Pro reported:
Snore index: 120
Duration: 11 mins
APAP pressure at the end of experiment: 10.5 cm H20
Total recorded snores: 120x11/60=30
Conclusion: Each stroke of the ruler generated a sound that propagated into the machine and was interpreted as a snore. This then had the same effect on the APAP pressure as true snores, raising it significantly.

Overall conclusions:
The snores reported by Encore Pro are individual snores. If a snore is broken into two during a breath it may or may not count as two. Coughing and talking ("tawgig" in CPAP parlance) do not affect the Snore Index, but the machine is sensitive to sounds caused by a sharp object dragging over the corrugations of the hose.

Now I've bored everybody to sleep... ZZZzzzzzz......
derek

Mikesus · Post by **Mikesus** » Sat Feb 19, 2005 7:32 pm

Ok, I actually read the manual and it says the flags are:

REMstar Auto Flags

Measurements are recorded in 30 second intervals.

rested gal · Post by **rested gal** » Sat Feb 19, 2005 7:35 pm

Derek, I love it!! What a neat set of experiments. And described so clearly. Very, very interesting.

wading thru the muck! · Post by **wading thru the muck!** » Sat Feb 19, 2005 11:12 pm

derek,

Great info! - I have seen the same significant pressure increases related to snores runs and also mask leaks. Do you have an over sleeve for your hose? My guess is this would likely eliminate the potential for false snores recorded as a result of inadvertent abrading of the hose. It’s very interesting to see that Respironics has incorporated functions in their algorithm able to eliminate coughs and speech from its snore detection. I've heard people also postulate that external noise from fans, televisions and pets may be causing false snores. It would be interesting to catalogue all such bedroom noises as safe or potentially troublesome.

I think -SWS is on vacation...he will be intrigued by you endeavors.

Snorenomore · Post by **Snorenomore** » Sun Feb 20, 2005 12:04 am

muck said

bedroom noises

I don't know about you, but when I have bedroom noises in mind, I'm not using my CPAP.

Snorenomore, a little frisky on Saturday nights!

rested gal · Post by **rested gal** » Sun Feb 20, 2005 12:34 am

LOL, snorenomore. Careful, or this entire board will get intrigued by YOUR endeavors instead of Derek's. rotfl!!

Liam1965 · Post by **Liam1965** » Sun Feb 20, 2005 6:13 am

Snorenomore wrote:I don't know about you, but when I have bedroom noises in mind, I'm not using my CPAP.

Yeah, me either, and since getting married again, I'm no longer ALONE, either. Much better.

Liam, who's talking about the noise of using his Nordic-Trak. What were YOU thinking?

wading thru the muck! · Post by **wading thru the muck!** » Sun Feb 20, 2005 10:37 am

Here, derek is trying to do some serious science (and quite well I might add) and all you guys just have your mind in the gutter, The next time I read one of the posts from someone who thinks now that they use cpap they'll never have sex again, I'll just send them to you guys and tell them don't worry.

Mikesus · Post by **Mikesus** » Sun Feb 20, 2005 11:31 am

Bedroom noises, hmmm... Like "Hey honey, you still awake?" Or the ever popular "Can you turn the light off?"

We have 2 kids, after the second one we learned better

Liam1965 · Post by **Liam1965** » Sun Feb 20, 2005 11:53 am

wading thru the muck! wrote:The next time I read one of the posts from someone who thinks now that they use cpap they'll never have sex again, I'll just send them to you guys and tell them don't worry.

Are you KIDDING? The mask is a HIT with the ladies. I'm getting a LOT more sex now than I was a year ago. I attribute it to the mask. The fact that I'm also married and wasn't then is just a coincidence.

Liam, whose wife now snores louder than he does.

loonlvr · Post by **loonlvr** » Sun Feb 20, 2005 1:09 pm

My questions is:what does snoring have to do with anything? I m only worried about apneas. Snoring may indicate apneas but its not revelant to what the data i want: lower ahi through fewer hypopneas and apneas. Maybe i m off base hear. Of course, I don t have a snore mate, er, bed mate.

wading thru the muck! · Post by **wading thru the muck!** » Sun Feb 20, 2005 1:17 pm

loonlvr,

I've found (and I think derek has also) that snores can cause the pressure on an apap to rise significantly. In dereks experiment it was 5cm. This has at times cause me to wake up ur have mask leaks.

loonlvr · Post by **loonlvr** » Sun Feb 20, 2005 1:26 pm

But can they be eliminated ?

wading thru the muck! · Post by **wading thru the muck!** » Sun Feb 20, 2005 1:36 pm

Hopefully minimized enough to not cause the machine to react inappropriately.

loonlvr · Post by **loonlvr** » Sun Feb 20, 2005 1:48 pm

And how is that accomplished. I make adjustments with my machine to lower ahi. Thats my main concern. I m not gonna change pressures to lower snore index if it affects my ahi.

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