1st Post, Hello! and a question.

[leemaisel]

Howdy Everyone!! Nice to find this forum!!!

I have been using my setup for over a year, and it's made a great deal of difference.

THe only thing is, when I first got my mask, (respironics comfortgel nasal mask) I had to physically open up the "vent" slit by breaking and repositioning it (because it was glued) and did not really allow any reasonable airflow that a human would produce during exhalation. It gave me serious headaches which I attributed to rebreathing my own CO2.. After opening it just a little more, testing it so that the pressure of the machine would not be lost, but still push out the exhalation, no more headaches!

I had forgotten about this, and recently ordered a replacement (same mask, it's Soooo comfortable) and was surprised when I hooked it up and realized the vent is WAY too tiny! so I had to modify it too. in fact, I believe the tolerance was even worse!

Are ALL masks made with insufficient vents? or non-adjustable?

I can't imagine that rebreathing your co2 can be very good for you.

THanks!

[linda b]

It is my understanding that ALL mask have a ventilation system for exhaling CO2. My only experience has been with the Comfortlite 2 and the Simplicity. Your problem may be related to initially becoming accustomed to breathing against the airflow. Several of the Respironics machines have C-flex which is a method of reducing the airflow momentarily while you exhale. Many people have found this to be very helpful while becoming accustomed to this therapy and some of them even turn off that feature later on. You might get more response to your question if you will post again and tell us which mask and machine you are using.

[rested gal]

Hi Lee,

What machine and what pressure are you using? Is your machine set to use "Ramp" which would make it start out at a low pressure then build up to your prescribed pressure?

If your machine is set for "ramp", many DMEs set the ramp to start as low as possible -- at 4 cm. That low a pressure can feel stifling to many people. Do you think too low a ramp pressure could be the cause of the problem you've had?

All cpap masks from any manufacturer are supposed to have received FDA approval (for whatever that's worth...lol ) and have a vent exhaust rate that the FDA considers safe for washing out exhaled CO2.

Of course there could always be a mask that came off the manufacturing line with the exhaust vent messed up, I suppose. Or maybe a few people do need a higher exhaust rate no matter what.

[leemaisel]

Machine: REMstar Pro 2 C-Flex CPAP Machine
Mask: ComfortGel Mask with Headgear
Humidifier: Remstar Integrated Passover Humidifier

Thanks!

No, I'm not using the ramp function, and my pressure is at 9.5cm I am using c-flex, so it senses my exhalations, and drops pressure accordingly.

However, you would not believe how small the slit for the vent on these masks were!

you seriously could not expect co2 of any appreciable amount to be expelled. I put the mask on, and blocked the hose port on the mask and was not able to breathe through it. So my theory is, if the exhaust port is that small, then all my exhaled air is going back down the hose when the pressure drops, and then SOME of it is re-inhaled.

However, by increasing the size of the exhaust port (just a bit) where more air can flow, then more will be forced out during the time between exhaling, and the pressure increasing. I have not opened it up enough to drop the pressure, it is working very well, but it was a scary discovery for sure.

[ozij]

Of course there could always be a mask that came off the manufacturing line with the exhaust vent messed up, I suppose. Or maybe a few people do need a higher exhaust rate no matter what.

In September orf 2003, (four years ago!) a small number of Comfort Gels did get messed up, and there was voluntariy recall by Respironics, who also contacted the FDA. The recall info was still on the mask's site in Feb. 2005, when I was trying to learn about the mask - which is why I remember it.

Here are some links to the FDA on that:

Firm Press release on FDA site

[url=http://www.fda.gov/cdrh/recalls/recall-092903.html[/url]Medical Device Recalls
Class 1 Recall: ComfortGel Nasal Masks

http://www.fda.gov/bbs/topics/enforce/2 ... 00826.html

RECALLS AND FIELD CORRECTIONS: DEVICES - CLASS I
_______________________________
PRODUCT
a) ComfortGel Nasal Mask size small. Recall # Z-0178-04;
b) ComfortGel Nasal Mask size medium. Recall # Z-0179-04;
c) ComfortGel Nasal Mask size large. Recall # Z-0180-04.
CODE
a) Part number 1009041; Lot numbers 030612, 130418, 030417,
030415,030409, 030321, 030320, 030316, 030312, 030311,
030310, 030306, 030305, 030303, and 030228;
b) Part number 1009042; Lot numbers 030604, 030603, 030528,
030520, 030501, 030422, 030421, 030408,030325, 030319,
030314, 030312, 030311, 030227, 030226, 020826, and
020823;
c) Part number 1009043; Lot numbers 030826, 030814, 030528,
030307, and 020822.
RECALLING FIRM/MANUFACTURER
Respironics, Inc., Murrysville, PA, by telephone on September 29, 2003. Firm initiated recall is complete.
REASON
Product does not contain built in exhalation port.
VOLUME OF PRODUCT IN COMMERCE
72 units.
DISTRIBUTION
Nationwide and Canada.

[leemaisel]

Also, my provider gave me a new mask (claiming they couldnt get the one I was using) and although it had a much bigger vent, it was so uncomfortable, I went back to the old one until I got a new one online.

[ozij]

Machine: REMstar Pro 2 C-Flex CPAP Machine
Mask: ComfortGel Mask with Headgear
Humidifier: Remstar Integrated Passover Humidifier

I put the mask on, and blocked the hose port on the mask and was not able to breathe through it. So my theory is, if the exhaust port is that small, then all my exhaled air is going back down the hose when the pressure drops, and then SOME of it is re-inhaled.

CPAPopedia Keywords Contained In This Post (Click For Definition): cpap machine, humidifier, hose, C-FLEX, Ramp

You blocked the hose port?? You mean, you tried to breathe only through the exhale vent? No wonder you couldnt' breathe. You're suppose to recieve air under pressure through that hose connection. Blocking the hose port means you get even less air than at a pressure of 4.

There is no reason to check a mask like that - as a matter of fact, some of the mask I've had warn not use them without a working machine, so certainly blocking them is a sure way of getting yourself suffocated.

Since you're using a auto, it compensates for the additional leak you created and your therapy pressure is not affected.

O.

[leemaisel]

LOL! You totally didn't understand what I was saying!

When I said I blocked the hose port, it wasn't during use! It was with my thumb just to determine how much air really flows through the exhaust port. In this case it was almost none. that's why I made it bigger. I wasn't wearing the thing blocked! Hehe!!

[ozij]

I did understand your test - but my point is that this test won't show you much, since there's air under blowing blowing through the system when you use the mask.

Different masks have different vent rates, as you can see on this table compiled by forum member dsm, based on data collected from forum members.

http://www.internetage.com/cpapinfo/leak-rates-1.html

This intentional leak rate (vent rate) rises as the pressure rises.

The numbers were taken from the various mask manuals.

O.

[leemaisel]

Ok, in trying to figure it out, I found THIS:

A length of hose 6 feet long by 1 inch in diameter would contain a volume of approximately 1,000 ml, which would represent added dead space to the respiratory circuit. In the normal situation, an alveolar ventilation of about 350 ml per breath is achieved by a tidal volume of 500 ml, 150 ml of which is wasted in normal dead-space ventilation. To sustain the same alveolar ventilation with the added dead space would require a tripling of the tidal volume.

In other words, the hose exceeds the lung capacity. Therefore, if the vent is not sufficient to expel the exhaled CO2 (by means of system pressure) then a majority of the exhaled CO2 will be re-inhaled over and over to a certain extent.

I really like the comfort of this mask, and although the other similarly designed mask had a much larger vent, i chose to widen the exhaust port a bit. The system seems to compensate (or function normally) for this.

Is it just me, or is anyone using this particular mask noticing the glued immobile vent is tiny?

[Snoredog]

Ok, in trying to figure it out, I found THIS:

A length of hose 6 feet long by 1 inch in diameter would contain a volume of approximately 1,000 ml, which would represent added dead space to the respiratory circuit. In the normal situation, an alveolar ventilation of about 350 ml per breath is achieved by a tidal volume of 500 ml, 150 ml of which is wasted in normal dead-space ventilation. To sustain the same alveolar ventilation with the added dead space would require a tripling of the tidal volume.

In other words, the hose exceeds the lung capacity. Therefore, if the vent is not sufficient to expel the exhaled CO2 (by means of system pressure) then a majority of the exhaled CO2 will be re-inhaled over and over to a certain extent.

I really like the comfort of this mask, and although the other similarly designed mask had a much larger vent, i chose to widen the exhaust port a bit. The system seems to compensate (or function normally) for this.

Is it just me, or is anyone using this particular mask noticing the glued immobile vent is tiny?

The hose dead space and volume capacity of it has no real bearing with your therapy using that machine. That information may be useful if you were using an AdaptSV for CSDB.

Mask and vent: The new ComfortGel exhaust "ports" have changed (actually some time ago) and there is no "Slot" any longer in the mask elbow system for the exhaust "ports". On the new style those exhaust ports are made up of those tiny square holes above the elbow in the main mask base in the center.

If you increased the diameter of those holes or added a slot somewhere you completely threw off the flow rate characteristics of the mask. That means the exhaust rate listed on the flow chart will no longer have any meaning, the leak rate shown by the machine won't be accurate. Hopefully the enlarged exhaust rate can still be compensated for by the machine in order to maintain dialed in therapy pressure. The machine will have to rev higher to compensate for that extra leak making things more noisy.

The "new" ComfortGel would probably feel much different (with the airflow) than the old style with exhaust ports built into the elbow, with its higher CO2 retention rate, it should feel more stuffy and/or warm with the incoming air.

[Findlater]

Hi leemaisel.. Great to hear that after a year of use you are getting good results.

As the nature of this site is about learning and adapting and general positive support , good on you for adapting your equipment to suit your requirements. (mentaly and physically)

I don't use your type of mask and have found no need to modify the one that I do have. I would like to thing that all the maths stuff has been sorted out on test dummy's .

But if a "small adjustment" + "good complience" = "Feel good "then you must have done ok!!!

Good on you for mentioning it to the group.

[leemaisel]

Heya Snoredog! Apparently the replacement mask that I ordered is of the OLD style, because it has the slot, and not the square holes.

I think I know why there was a redesign though.

[GeneS]

It is good if you can check your vent rate with software like encore. It will verify that you are venting properly. Does your machine have data capability. I do not remember what flow is considered adequate to flush the co2 but it varies with manufacturer and probably varies with lung capacity. The intentional vent rate is determined by orifice formulas. The flow increases with increased pressure drop across the orifice (cpap pressure), area of the opening, and a co-efficient that depends on the shape, smoothness, etc. of the opening. It is not effected by volume in the hose. If people have lower pressures they have a lower vent rate so flush less c02. If I had low pressure I would get a mask with higher vent rates or get a little creative like you did.
GeneS