Anyone else sensitive to flow loss with humidifier?

For most of the year I do not use the humidifier or Climateline hose on my S9. When the air gets dry, as now when we have the AC on I add the humidifier back on.
What I really notice is the loss of air flow. It seems really restricted as opposed to when I use a Slimline hose and no humidifier.

I wonder if it is just a sensation due the the more dense air laden with humidity??
Whatever it is, it takes me several nights to get used to it.

Brian wrote:For most of the year I do not use the humidifier or Climateline hose on my S9. When the air gets dry, as now when we have the AC on I add the humidifier back on.
What I really notice is the loss of air flow. It seems really restricted as opposed to when I use a Slimline hose and no humidifier.

I wonder if it is just a sensation due the the more dense air laden with humidity??
Whatever it is, it takes me several nights to get used to it.

what do you mean 'loss of air flow'?

you shouldn't have any airflow sensation normally, just the pressure to help you breath.

it's not a leaf blower!!!

Exactly what I said.
The volume of air flow is noticeably less with the humidifier and or Climateline hose. Back to back comparison reveals it.

I know it's not a leaf blower. I've been on xPAP for over 15 years and kind of know what to expect.
The humidifier and hose on the S9 cause some restriction.

Hey Brian - what temp/humidity are you using in the summer? I found that turning off heat and turning down humidity (off and 2 in ResMed speak) the air felt marginally less "heavy" - but I have never used my system without the humidifier.

I can't stand to have my head under a cover on account of the humid air, and it seems like the air flow is reduced. So I think you are correct that the more humid dense air is to blame for your discomfort. Looks like a choice between sore nostrils and loss of air. Incidentally, I use a humidifiier to quiet my system, but with no water in it.

Brian wrote:Exactly what I said.
The volume of air flow is noticeably less with the humidifier and or Climateline hose. Back to back comparison reveals it.

I know it's not a leaf blower. I've been on xPAP for over 15 years and kind of know what to expect.
The humidifier and hose on the S9 cause some restriction.

if you're comparing the perceived volume of air that blows out the side of the flow generator when you turn it on with nothing attached with the perceived volume of air that you get through the humidifier and a hose (and mask), then all I have to say is "so what?, that means nothing"

as I said, it's not a leaf blower, it's not about how much air it can blow, it's about providing a pressure level *at the mask*. and the machine's algorithms take into account the humidifier, hose size, hose length, and even mask openings to provide the desired *pressure* at the mask.

if you're complaining that it behaves differently than your 15 year old machine, then all I've got to say to that is 'apples and oranges'.

your system is providing the same 20-40 liters per minute of airflow that vents through the mask whether you're using the humidifier or not, (unless you filled the chamber with a sponge or something weird) and it automatically adjusts to the climateline size when you attach it.

Brian wrote:For most of the year I do not use the humidifier or Climateline hose on my S9. When the air gets dry, as now when we have the AC on I add the humidifier back on.
What I really notice is the loss of air flow. It seems really restricted as opposed to when I use a Slimline hose and no humidifier.

I wonder if it is just a sensation due the the more dense air laden with humidity??
Whatever it is, it takes me several nights to get used to it.

Are you using an external humidifier? If not do you normally have the Resmed chamber connected even when you don't use water?

There will be a slight pressure loss with an increased volume (chamber + or hose) which may be what you are feeling?

The sensation is that when I have the humidifier and Climateline hose on, I can inhale faster than the machine can provide air flow. Without the humidifier and the standard hose I don't have this issue. It's something that I notice when I first get into bed and prior to my breathing slowing down, I take a few deep breaths.
That's when I realize it.

There are two items at play, pressure and volume. The volume seems restricted.

I'm not complaining, just sensitive to the difference. I've had the S9 for several years, it has been that way since I've had it.

Did a little digging and found this in the clinicians manual.



So, I'm not imagining things, I wouldn't think I would notice the difference...

I had the reverse happen to me, that is, slightly reduced air flow with the H5i humidifier connected. Personally, I much prefer the air flow characteristics with the humidifier connected.

During the summer, I’ve been using the S9 AutoSet with the H5i humidifier and a standard sized hose. I recently went on a trip for a few days and chose not to bring the humidifier along. Interestingly, the first thing I noticed after putting on my full face mask without the humidifier connected was that it sounded like there was what I’ll describe as some ‘wind turbulence’ or a mini ‘wind storm’ going on in my mask. I determined that the noise was being created by the steady air flow streaming out of the mask vent holes, but for some reason the flow rate was most definitely higher, albeit slightly. I found this most interestingly as I had not changed any of my S9 settings and a careful examination of the mask didn’t reveal any problems had developed. In fact, I verified on the S9 AutoSet LCD that the initial pressure was ramping up from 4.0 cmH2O as expected. This new noise issue was immediately noticeable every night when I put the mask on and suggested to me that the blower in the S9 was able to ‘push’ more air at 4.0 cmH2O compared to with the humidifier connected. As a result of the larger volume of air flowing out of the vent holes, noticeably more ‘noise’ was created. Fortunately the wind noise faded into the background after falling asleep. Another possibility is that a slight amount of air leakage may also occur when the H5i humidifier is connected such that the mask pressure is slightly lower when using the humidifier, or a combination of leakage, pressure loss and increased resistance to mass air flow.

Upon getting back home, I returned to using the H5i humidifier again and I immediately noticed the wind turbulence was gone. In actuality, a steady stream of pressurized air was still exhausting out the mask vent holes as always, but the flow rate was sufficiently reduced such that it wasn’t noticeable any more, at least not at the initial lower starting ramp pressure(s) being experienced while I was waiting to fall asleep.

After some thought along with examining how the humidifier interfaces with the S9 AutoSet, I rationalized that the air flow at the mask is reduced slightly due to the circuitous path the pressurized air takes with the H5i attached. That is, without the H5i humidifier connected, the pressurized air simply flows directly out of straight connector on the S9, though a smooth hose with very gently curvature and onto the mask. What could be easier? However, with the H5i connected, the air path is altered such that it flows out of the S9, into the humidifier through a 3” long tapered rectangular port, turns 90 degrees downward through a circular orifice into the water chamber, turns 90 degrees to travel across the surface of the water, turns 90 degrees upward towards the exit port and finally turns another 90 degrees as the air exits horizontally out of the chamber and into the air hose. In all, the air turns through 360 degrees travelling through the H5i humidifier and the added resistance (akin to back pressure) has the effect of slightly reducing the air flowing into the mask and out the vent holes.

Sorry for the long and detailed post. My point is that there is definitely a difference in the air flow characteristics with, and without, the H5i humidifier connected. This appears to be consistent with the manufacturer's data.

Robert

Thanks for that - I could not get my brain to recall enough high school physics to know if flow rate could vary independently of pressure. It appears it can and sanity is restored.

Brian wrote:The sensation is that when I have the humidifier and Climateline hose on, I can inhale faster than the machine can provide air flow. Without the humidifier and the standard hose I don't have this issue. It's something that I notice when I first get into bed and prior to my breathing slowing down, I take a few deep breaths.
That's when I realize it.

There are two items at play, pressure and volume. The volume seems restricted.

I'm not complaining, just sensitive to the difference. I've had the S9 for several years, it has been that way since I've had it.

Well that explains it much better. The climateline hose is much smaller in diameter and restricts the flow thru the hose. When the climateline is plugged in it is sposed to change something in the blower to compensate for that restriction. I think it increases the pressure.

Perhaps that climateline hose feature is not working on your machine. Try bumping up the pressure a bit yourself to see if that helps you.

Guest wrote:

Brian wrote:The sensation is that when I have the humidifier and Climateline hose on, I can inhale faster than the machine can provide air flow. Without the humidifier and the standard hose I don't have this issue. It's something that I notice when I first get into bed and prior to my breathing slowing down, I take a few deep breaths.
That's when I realize it.

There are two items at play, pressure and volume. The volume seems restricted.

I'm not complaining, just sensitive to the difference. I've had the S9 for several years, it has been that way since I've had it.

Well that explains it much better. The climateline hose is much smaller in diameter and restricts the flow thru the hose. When the climateline is plugged in it is sposed to change something in the blower to compensate for that restriction. I think it increases the pressure.

Perhaps that climateline hose feature is not working on your machine. Try bumping up the pressure a bit yourself to see if that helps you.

From the chart I posted, as pressure is increased, flow goes down. Bumping up pressure will make it worse.
From ResMed's own chart, it looks like there is no mompensation feature as you mentioned.
Also, I've never use the ramp feature. I like full pressure immediately.

From a pure physics (pneumatics) perspective, air pressure and flow vary in direct relationship to one another. That is, if the pressure is increased across an orifice the flow rate through the orifice will correspondingly increase.

As for the S9 and/or any CPAP / APAP, the small sized blowers understandably have a limited capacity and a compromise exists in their ability to produce both pressurized air and high levels of mass air flow at the same time. While the blower characteristics are well suited for the task at hand, limitations understandably exist. While the small 'blowers' are able to compensate for modest changes in resistance to flow (back pressure) over the range of pressures the machine is designed to operate at, the blowers are not near powerful enough to totally overcome high levels of flow resistance. In fact, it's not uncommon to be able to completely stall a fractional horsepower blower if the flow resistance becomes too large, no different than folding a garden hose in half to stop the water flow.

If you're so inclined, you can try taking the air hose of the mask and putting you hand over the end off the hose for a few seconds to create a high resistance to air flow, or a complete blockage in this example. When you do this, take notice of how the blower reacts to the change in air flow resistance.

When you think about it, you wouldn't want a Tim the Toolman sized blower. Such a blower would have the ability to cause harm by having the potential to develop and generate a lethal amount of flow at any pressure. Clearly, this is not something a CPAP designer would want to deal with, and fortunately does not need to deal with.

I always find it interesting how some people respond better to constant pressure settings while others perform better with variable auto adjusting pressures. Ditto for the ramp function. I personally love it as it really buys me time to fall asleep without being aware that I'm wearing a pressurized mask. Perhaps this is more beneficial for those of us who wear a full face mask?

Robert

Brian wrote:

Guest wrote: When the climateline is plugged in it is sposed to change something in the blower to compensate for that restriction. I think it increases the pressure.

Perhaps that climateline hose feature is not working on your machine. Try bumping up the pressure a bit yourself to see if that helps you.

From the chart I posted, as pressure is increased, flow goes down. Bumping up pressure will make it worse.
From ResMed's own chart, it looks like there is no mompensation feature as you mentioned.
Also, I've never use the ramp feature. I like full pressure immediately.

Somewhere in the resmed literature it should explain the use of the climateline hose and how it should work. Since I don't have a resmed I won't be doing any research on that but you may want to or just call your DME and explain what is going on. It seems no one else is experiencing this.