Do Hypoallergenic filters lower the output pressure in a ResMed S9

[zonk]

AirSense 10 have a setting for antibacterial filter

AB filter ... Select Yes if you attach an antibacterial filter .... No / Yes

[LesPauloholic]

Thanks Everyone!

[omega2498]

IIRC, There is a setting in the S9 for the antibacterial filter.

No such setting to my knowledge, the only setting to do with filters is a reminder option when to replace the filter but got nothing to do with the antibacterial filter

According to ResMed "Antibacterial filters are not compatible with the ClimateLine, ClimateLineMAX or SlimLine tubing but can be used with the Standard air tubing". Also ResMed warn "Blocking the air tubing and/or air inlet of the S9 device while in operation could lead to overheating of the device.

10.25 am, time for morning

Interesting for a UK Engineer who used to do long distance pipeline pressure drop calculations .......I have a Resmed S9 CPAP with Slimline tube and suffer with allergies, especially tree pollen. I bought a Respironics Bacteria filter P/N 342777 (also says ref 342077 on the packet just to confuse things). I hoped this might reduce the micron size fragments of tree pollen getting into my airways. I did a flow test without the mask in place - there is a marked reduction in flow when the filter was placed on the delivery port on the S9. As the machine presumably senses the pressure at the machine, rather than at the mask, I presume this type of filter does reduce the pressure at the mask, as there is no feedback loop from the actual mask pressure back to the blower :-( ?? So basically I think my actual pressure at the mask will be less than my Clinician recommended 8 cm H2O if I use the filter ...... :-(
(Of course - flow with mask fitted will be much lower than the free air delivery)
Has anyone used a manometer to actually measure the pressure drop across this type of filter at typical breathing flow rates ?)

[FrankNichols]

What about making a large box with a large filters built into it to place the CPAP machine into - that would not affect the exit pressure and the intake would not be limited if the filters are large enough. I expect a card board box, or simple plastic aquarium could be used, and I am not a expert or filters, but would HEPA filters work? Or the air conditioner filters that claim to reduce bacteria and pollen? I expect a small aquarium a AC filter over the top and a small hole for the hose to come out could all be done for $50 or less.

[vsheline]

What about making a large box with a large filters built into it to place the CPAP machine into - that would not affect the exit pressure and the intake would not be limited if the filters are large enough. I expect a card board box, or simple plastic aquarium could be used, and I am not a expert or filters, but would HEPA filters work? Or the air conditioner filters that claim to reduce bacteria and pollen? I expect a small aquarium a AC filter over the top and a small hole for the hose to come out could all be done for $50 or less.

And as an added benefit, the hypoallergenic filter at the input of the machine would need to be changed hardly ever, since it would be kept clean by the huge external filter(s).

[archangle]

I did a flow test without the mask in place - there is a marked reduction in flow when the filter was placed on the delivery port on the S9. As the machine presumably senses the pressure at the machine, rather than at the mask, I presume this type of filter does reduce the pressure at the mask, as there is no feedback loop from the actual mask pressure back to the blower :-( ?? So basically I think my actual pressure at the mask will be less than my Clinician recommended 8 cm H2O if I use the filter ...... :-(
(Of course - flow with mask fitted will be much lower than the free air delivery)
Has anyone used a manometer to actually measure the pressure drop across this type of filter at typical breathing flow rates ?)

First, let me point out that we're discussing the antibacterial filter that goes on the output of the blower, not the hypoallergenic filters this thread is about.

Testing without the mask is not that meaningful. The machine will probably be running the fan at maximum speed because it can't keep the pressure up. The pressure will not be constant at the output of the CPAP. With the mask in place, the flow rate will be much lower, and the machine will regulate the output pressure to a fixed value. Pressure drop through the filter goes up with flow rate. It's not exact, but I think pressure drop is roughly proportional to the square of the flow rate, so the difference between mask and no mask will be larger than you expect.

The question is more complicated than it appears at first. When you inhale, the flow rate will be higher through the bacteria filter, so the pressure drop will be higher. When you exhale, the flow rate will drop, and may actually go below zero. In that case, the pressure at the mask will be higher than the output of the blower. When you're in apnea, flow through the filter will be equal to the leak rate of your mask, probably 20 l/m or less.

Note that this is sort of a negative Flex/EPR/exhale relief function.

The effect of the varying pressure at the mask on your apnea is hard to predict, but the average pressure will be lower.

I think I've heard numbers about pressure drop being around 1 to 2 cmH2O. Yet another reason that it's good to have an APAP machine. It would try to adjust pressure to compensate and keep your AHI down.

I suspect that the antibacterial filter will affect the ability of the machine to distinguish central apnea, and maybe to do EPR/Flex/bilevel/BiPAP/ASV/etc. Snore detection might also suffer, which would affect APAP adjustment. Flow limitations might also be affected.

In practice, I suspect it's not too big a problem, but if you have a fully data capable machine, it shouldn't be too hard to change your pressure settings to adapt. You might also need to use or increase your EPR/Flex/bilevel pressure support a bit.

For the hypoallergenic filters that go on the air input to the machine, the machine should sense the pressure at the output of the machine to compensate unless you have really dirty filters.

[archangle]

What about making a large box with a large filters built into it to place the CPAP machine into - that would not affect the exit pressure and the intake would not be limited if the filters are large enough. I expect a card board box, or simple plastic aquarium could be used, and I am not a expert or filters, but would HEPA filters work? Or the air conditioner filters that claim to reduce bacteria and pollen? I expect a small aquarium a AC filter over the top and a small hole for the hose to come out could all be done for $50 or less.

The input air filters won't affect air flow much if at all, unless they're really dirty. The antibacterial filter on the blower output is a different question.

[Asjb]

I would put the filter right at the output of the machine since this is the lowest "impedance" point, not near your mask.

That probably apply to the antibacterial filters, not to hypoallergenic or standard filters

Hello Zonk. That's my understanding also - only antibacterial can effect the pressure, not the hypoallergenic (at least for Resmed - don't know about other machines). I've been using hypoallergenics for some time and no effect on the pressures needed or on the 'feel' of the machine, but they certainly seem to catch more particulate matter - they go from white to dark grey within a week. We're unfortunately in pollen season at the moment.

.............................................

My current pressures: ASV auto. EPAP 11.6-14. PS 3-10.

[archangle]

Hello Zonk. That's my understanding also - only antibacterial can effect the pressure, not the hypoallergenic (at least for Resmed - don't know about other machines). I've been using hypoallergenics for some time and no effect on the pressures needed or on the 'feel' of the machine, but they certainly seem to catch more particulate matter - they go from white to dark grey within a week. We're unfortunately in pollen season at the moment.

A few small caveats.

If the input filter gets dirty enough, it will eventually decrease the output air flow past the point where the fan can adjust. I know a really dirty filter will cause some machines to overheat. Some machines will shut down if the air inlet is blocked.

I think some of the really old machines either didn't sense output pressure or didn't adjust much for it. I think they just ran the fan at a certain speed. For instance, if you set it at 4 cmH2O, and take the hose off, it doesn't blow a large blast of air, like you'd expect it to do if it was trying to maintain the pressure.

I suspect such machines won't do a good job of maintaining pressure with a dirty filter.

That was a 12 year old CPAP machine, though. I think almost all newer ones do better at maintaining pressure.

[omega2498]

LesPauloholic ,

I am going to install one tonight on my new S9 Autoset. The filter would only cause a very subtle pressure drop IF the flow rate was very high. I would put the filter right at the output of the machine since this is the lowest "impedance" point, not near your mask. I prefer to breath the cleanest air possible due to my allergies. If anyone if interested I can measure the pressure drop at the highest flow rate that the machine is capable of producing. Jay

Jay, I note that you have a pressure gauge in your system. What sort of pressure drop does the `after filter' introduce at normal breathing rates, and have you upped the output pressure of your CPAP to compensate for it. I could find no data on pressure drop vs flow for the Virobac II on the Web :-( I have one of these filters packaged as a Respironics bacteria filter part number 342777. regards user Omega2498.