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Breathing through a straw
#1
I have a ResMed s9 and pressure setting of 11. It works great and I love it. I recently bought a ResMed S8 for the firehouse because traveling with my S9 every third night is a pain.

When I use the S8, although the pressure is the same and I had it tested at a local CPAP store, it feels like it's only 2/3 of the S9. I can barely sleep. I tried different tubing and nasal pillow size with no improvement. The tech at the store says my S9 is blowing 150 lpm but he doesn't know what the S8 is blowing.

I don't think I need more pressure but I might need more volume. Any suggestions???
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#2
Ok, #1. the tech tested the S8 for same pressure as the S9.

How did he do this? With a separate manometer?

#2. How is he able to tell you the S9 is moving 150LPM but not the S8?

If he can use a manometer and an anemometer the solution should be fairly easy.
Didn't he get any math in high school?

I am as perplexed as you, CDF.

Dont-know
"With ordinary talent and extraordinary perseverance, all things are attainable." - Thomas Foxwell Buxton

Cool
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#3
The tech used the manometer for both. I had them both with me at the store. He tested the S9 and then removed it and tested the S8. Both registered exactly 11.0. While I was sitting there, I put each machine on and the S9 sounded like a tornado compared to the S8.

He used a chart from the S9 instruction manual to estimate the LPM but didn't have a manual for the S8 so he couldn't tell me.

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#4
I also tried several different hoses and nothing really changed. The store apparently didn't have an anemometer.
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#5
Hi CFDRich,
WELCOME! to the forum.!
Hang in there for more suggestions and best of luck.
trish6hundred
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#6
If I'm not mistaken, the S8 uses the standard CPAP tubing which has a larger diameter than the S9's "SlimLine" tubing. Imagine that you have a cup of water and two straws: a thick one and a thin one. If you blow into each straw to make bubbles in the water, does it feel the same? Probably not. It takes more effort to blow through the thin one and it sounds louder (a moot point for CPAP when the mask is on).

If you're comparing the air coming out of the two open hoses, I would expect them not to sound or feel the same. The important thing is that they both register correctly on the manometer.
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#7
(08-12-2013, 03:45 PM)CFDRich Wrote: I don't think I need more pressure but I might need more volume. Any suggestions???

The thing is, a CPAP machine will deliver whatever volume flow rate (liters per minute) is necessary to maintain the set pressure. You couldn't change the flow rate without changing the pressure, too.

I don't know much about the ResMed machine but I would check that they're both set for the same type of hose.

The tech is measuring the static pressure, that is, the pressure when you're not inhaling. It could be that the machine is not capable of maintaining that pressure when you inhale.

Others have posted on the noisiness of the S9. It seems some are more noisy than others.
Sleepster
Apnea Board Moderator
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#8
(08-12-2013, 07:19 PM)Sleepster Wrote: The tech is measuring the static pressure, that is, the pressure when you're not inhaling. It could be that the machine is not capable of maintaining that pressure when you inhale.

Sleepster, that makes sense but then why do they only test the machines with manometers if they can pass that test but still fail to maintain IPAP? Seems like a half-done test.
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#9
(08-12-2013, 07:28 PM)Paptillian Wrote: Sleepster, that makes sense but then why do they only test the machines with manometers if they can pass that test but still fail to maintain IPAP? Seems like a half-done test.

Simple. Within the machine. there will be a control loop that periodically takes the measured pressure from a pressure sensor, compares it to the commanded value, and adjusts the airflow appropriately to maintain the commanded pressure.

The question is not whether the machine is capable of providing the airflow. I'm hard-pressed to come up with a realistic failure mode that provides some airflow but not full airflow without obvious things like bearing grinding noises. The question is whether the pressure sensor is calibrated correctly. And that can be determined using just the static test.
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#10
(08-12-2013, 07:28 PM)Paptillian Wrote: Sleepster, that makes sense but then why do they only test the machines with manometers if they can pass that test but still fail to maintain IPAP?

It's just one simple test. There was a poster here a while back who had a manometer connected while he was breathing so he could monitor the pressure in these situations.

You can get a used PRS1 APAP (Model 550) pretty cheap. It's a newer model than the S8. Check Supplier #2.

Sleepster
Apnea Board Moderator
www.ApneaBoard.com


INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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