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[Equipment] Is larger diameter tubing quieter than smaller diameter tubing?
I have seen references to three hose/tubing sizes (diameters), i.e., 15mm, 19mm and 22mm. Are there really three sizes, more than three sizes or just different ways of referring to the tubing, inside versus outside diameter, perhaps?

For example, I have seen ResMed ClimateLine tubing called 15mm and ClimateLineMax tubing called 19mm. I have seen ResMed SlimLine tubing called 15mm and regular tubing called 22mm.

I hypothesize that larger diameter tubing should provide
  • better air flow, i.e. less resistance, allowing the xPAP unit to operate less forcefully and possibly less noisily, to deliver the required air volume, and
  • less noise due to air movement
than smaller diameter tubing. I surmise the same holds true of tubing with a smooth inner wall versus tubing with a ribbed inner wall.

So would I be right in concluding that larger diameter (and possibly smooth-walled) tubing will result in noticeably quieter operation of xPAP units than smaller diameter (and possibly ribbed) tubing?

I'll try to test my hypothesis once I acquire some slimline tubing but that may be a while yet.
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most of my noise seems to come from the vents on the masks, and the different masks have a marked difference in noise level. Not that its that loud anyway - my wife is delighted with how quiet the whole set up is.
I cannot hear my machine over it. I do not really think the hose would make a noticeable difference, but then - I haven't tested it.
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Yes, there are three different sizes.

SlimLine and ClimateLine are the same diameter and thinnest.
Standard is next size up.
ClimateLine Max is largest diameter, but there is no setting for it on the standard CPAPs and APAPs and is intended for use at pressures over 20cmH2O with bi-level and ASV machines (which do have settings for it).
SlimLine, ClimateLine and ClimateLine Max all have smooth interior walls, they are only ribbed on the outside. I'm not sure about standard hoses, but pretty sure most are smooth on the inside as well.

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Well, I found some info in the various manuals and from measurements and observations.

All the (non-heated) tubing I have (Respironics 1032907 & 622038) is slightly ribbed on the inside due to its spiral construction and measures 22 - 23mm od (outside diameter) and 19mm id (inside diameter). I have no ClimateLine tubing, yet.

For the ResMed S9 Autoset, apparently, the air outlet is listed as 22mm but that is the outside diameter (od) measurement. Its inside diameter (id) measurement is 19mm. The Philips/Respironics System One REMstar AUTO 560's air outlet measures 22mm od and 18mm id on the unit I am currently trialing. My old Respironics ResMed Auto M's air outlet measures 22mm od and 19mm id.

For the ResMed S9
  • SlimLine (15 mm inner diameter)
  • Standard (19mm inner diameter)
  • ClimateLine (15mm inner diameter, with the H5i humidifier) and
  • ClimateLineMax (19mm inner diameter, with the H5i humidifier)
air tubing can all be used.

The S9 automatically sets the tubing type if the ClimateLine (15mm) or ClimateLineMax (19mm) is used. Otherwise it must be set for SlimLine (15mm) or Regular (19mm) tubing. I suppose 22mm tubing cannot be used with the S9 series.

Also apparently, the S9 is slightly quieter without the H5i humidifier than with.

Also apparently, and counter intuitively, without the H5i, the sound pressure level, ISO 17510-1:2007, is 26dBA using the SlimLine tubing and 27dBA using the Standard tubing. While the difference between 26 and 27 dBA is essentially negligible, the fact that the SlimLine's value is lower is surprising. The sound power level, ISO 17510-1:2007, is also 1 dBA quieter for the SlimLine than the Standard, without the H5i. [Unless there should have been a minus sign in front of the dBA values. Or does SlimLine tubing have a smooth interior and Standard a ribbed interior?] If the H5i is used there seems to be no difference between the two tubing types.

For the Philips/Respironics System One REMstar AUTO 560, 15mm, 22mm or 15mm heated tubing can be used, according to the manual.

Yet my Respironics tubing (1032907 & 622038) measures 22m od and 19mm id. So what is the 22mm tubing mentioned in the Respironics manual. And where does my 19mm id Respironcs tubing fit it? Is it usable on the System One?
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I know that from the physics, the narrower, ribbed tubing should intuitively be the loudest and have the higher flow resistance...but the thing we need to remember is that with CPAP, our pressure and flow rates are pretty low, especially for the diameter of the tubing.

Compare oxygen tubing at the same flow rate as our CPAPs, and yes, the narrower tubing will be tons noisier Smile
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I think the biggest difference is that larger diameter tubing makes it easier for the CPAP machine to estimate and control the pressure at the mask, especially in terms of quick changes in pressure between inhale and exhale.

Newer machines have smarter computers, better sensors, and better blowers that allow them to compensate for the drawbacks of smaller diameter tubes.
Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
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