We've updated our privacy policy.

Negative Input

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 8 days ago Original Poster Sleep Enthusiast

Negative Input

Status report:

Waking.

Reason:

Unknown

Light sensor report:

Negative.

Proximity sensor report:

Negative.

Sound recorder report:

Negative.

Pain sensor report:

Negative.

Run internal diagnostic:

Confused, dizzy, not breathing.

Command: Initiate breathing.

Status report:

Situation worsening.

Seek cause:

Breathing failed.

Command:

Breathe harder and monitor outcome.

Outcome report:

Air intake totally blocked!

Emergency:

Confusion and dizziness, darkness encroaching, must act immediately!

Urgent command:

Displace mask and chinstrap!

Status check:

Returning to normal.

Equipment check:

Mask attached and intact CPAP powered but turned off.

Cause of shutdown:

Unknown.

Turn CPAP on, test mask:

Fully operational.

Turn off, test mask:

Can't breathe.

Analysis report:

Mask failure caused when Silicone tubing closes with negative input.

Conclusion:

Unacceptable risk.

Require improved equipment and early warning systems.

2,314 posts
bio
Was this reply useful? Learn more...
   
[-]
Sierra +0 points · 8 days ago Sleep Patron

It may depend on your specific mask. My wife has had failures with her ResMed S9 and has survived them for surprisingly long periods of time.

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 8 days ago Original Poster Sleep Enthusiast

Howdy Sierra,

The mask in question is the Airfit P30

Yes both of my machines have shut down in the middle of the night from time to time and it can leave you pretty wrecked, but there is some air that can still be sucked through the machine and the outlet valve and, of course, there are often leaks which can all add up to enabling you to survive for long enough to wake up and deal with the problem, albeit with a bit of a headache.

The Airfit is different. I have tested it numerous times now and if you are lying on your back it does still allow a tiny amount of air through the two depressed tubes, if you don't suck too hard, but if you are on your side with one tube already closed the other tube closes totally due to the negative suction.

It leaves you with absolutely no air intake at all.

Most masks would only pose a serious risk to somebody who was a really heavy sleeper, or if the machine failed at a critical point in a sleep cycle, but the Airfit is a much more immediate risk to a far wider range of CPAP uses.

Other than it's lethal potential it is a very comfortable mask, and works really well for me, so what could I do to minimize the risk?

I gather that the more recent machines can be self starting which would be helpful in a very short outage.

There are also power outage alarms which might be useful although I think that both of my machines are capable of shutting down without the excuse of an outage.

Are there alarms for pressure loss?

I will attempt to adapt the existing mask to prevent the side tubes from collapsing under negative pressure but why have the manufacturers not already considered all of this?

Don't they have some obligation to make sure their products are safe?

2,314 posts
bio
Was this reply useful? Learn more...
   
[-]
Sierra +0 points · 8 days ago Sleep Patron

I would expect the mask should have a vent system right on the mask that should allow an emergency amount of air into the mask. The ResMed machines show a mask pressure but they do not measure the actual mask pressure. It is just calculated using the machine pressure and flow rate. The ResMed machines also has a SmartStart system which will restart the machine based on flow in the tube(s) but if they are plugged then I am not so sure. That is about all I can think of.

3 posts
Was this reply useful? Learn more...
   
[-]
jamesnumpana +0 points · 7 days ago

Hi Sierra, I agree about the vents to allow emergency air in , I’ve seen a few appliances that have that. Regardless of what the machine says or does , there needs to be safety incorporated for emergency situations. I absolutely hate using the straps due to claustrophobia so I bought this sticky silicone flaps that sticks to my cheeks and holds the mask in place. Not perfect but it eases my fear that I’ll run out of air and not be able to find my hands, wrestle through the sheets and doona and figure out how to get the straps off my head in time to breath. I can see why 50% of CPAP starters give up within a year.

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 4 days ago Original Poster Sleep Enthusiast

I havent read up on any of the technical stuff but it would seem, to my limited understanding, that these machines dont have a separate flow meter although they probably extrapolate flow from the energy used to maintain pressure.

Most of the machine's functions are keyed to the pressure monitor.

They have some general calculations and automatic adaptations such as an assumed pressure loss of so much between the machine and delivery through varying mask types and those parameters should be largely unaffected by venting systems because the machine would just have to work harder to overcome the continuing pressure loss.

I would guess that if the machine has autostart capabilities the process of putting a mask on would cause pressure fluctuations at the pressure sensor signaling the machine to start and the absence of any fluctuations over some seconds would signal the machine to shut down.

Trying to figure out how the machine functions would be essential to understanding the possible impacts of changing the designed parameters of masks and venting systems.

If any of the above is correct slightly increasing the venting capacity of a mask might register as a perpetual leak and cause the machine to work harder but it should not significantly affect the pressure that is being delivered or any of the autostart functions.

All of which is irrelevant because it would be unwise to tamper with any of this equipment.

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 8 days ago Original Poster Sleep Enthusiast

The mask vent is above the soft tubes that suck flat.

It is on top of the head where the main hose to the machine connects.

You can breathe out quite easily with no resistance but the tubes are a one way valve.

Hence my statement that it leaves you with absolutely no air intake at all.

Wander into your nearest CPAP shop and you can test one for yourself. Pop the mask on and hold your hand or a pillow against one cheek and try to breathe.

Paradoxically it is a brilliantly conceived design for comfort and fit and effectiveness under pressure.

Perhaps the prototype used a different grade of silicone but the product that Resmed are selling is dangerously flawed.

It would not be of such a concern to me if I thought that natural reflexes would safeguard the user but they don't.

I use a chinstrap which, arguably you could negate, but that would take a positive instruction.

It would require, not just a reflex to allow the mouth to open, but a conscious choice to actively open the mouth against the tension of the chinstrap and to hold it open against the constant pressure.

It is not a natural and instinctive, unconscious response.

With other masks you have some time to muddle your way to consciousness and remedy the situation but with this mask there is no time.

The initial layout of this thread was designed to show the necessity for a number of steps from emergency wakeup to becoming fully conscious and reactive to urgent circumstances and it could be argued that normal masks do allow enough time for most CPAP users to rectify the problem and recover from the impact but only because there is still a limited airflow. It does not allow for the limitations of zero airflow and it does not allow for the added delays caused by increasing confusion and disorientation and other symptoms of oxygen deprivation nor does it allow for the added liability caused by using CPAP on patients who are already confused or irresponsive due to varying levels of disability or dementia.

I don't doubt that there are situations where SmartStart would prove useful but how many power outages would be short enough for you to hold your breath through them and what about when the shut down is initiated by the machine itself and what if something simple and common happens like the primary hose wriggles loose?

The machine is happily blowing air into infinity and you've had your last gasp.

No matter how many safeguards you put in place the risk still remains in a mask design that can totally obstruct all airflow.

It seems to me that the Resmed Airfit mask is, in itself, inherently dangerous.

3 posts
Was this reply useful? Learn more...
   
[-]
jamesnumpana +0 points · 7 days ago

I’m new to this CPAP caper but there are lots of regulations that cover selling therapeutic goods, however you are entitled to survive using a product. There’s a volume of exhaled breath called ‘dead space’ between the mouth and the great outdoors with some mouth, mask and nose appliances having perforated ports so the exhaled air is immediately dispelled. When there is zero positive pressure these perforations allow for a minimal amount of air to be drawn in while you struggle to the surface. Is the problem the machine, the side tubes or something else ? If it’s just the tubes then it is something the ‘design guys’ should be made aware of. It sounds like you’re having a terrible experience.

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 7 days ago Original Poster Sleep Enthusiast

Hi jamesnumpana

While I appreciate your sympathy I really am not having a terrible experience, just another puzzle that needs solving, another issue to wrestle with in the frail hope that raising the subject might somehow make a difference.

Some get lost in detailed discussions about ramps and relative pressures and the ideal cleaning routines but I prefer to question the underlying assumptions and the wider parameters.

I like writing and I enjoy a challenge even though it achieves very little in the way of apparent results.

2,314 posts
bio
Was this reply useful? Learn more...
   
[-]
Sierra +0 points · 7 days ago Sleep Patron

When you were talking about the mask I was thinking it was the minimal full face type, but I see it is just on the nose. I also see that it comes in two versions the Nasal and Pillows. Both appear to have some venting on the nasal part as well as at the top of the head. I wonder if one style may have more venting at the nose compared to the other? The drawing from the manual also seems to suggest the QuietAir vent on the pillows version is removeable. I wonder if it would provide more venting if you removed the QuietAir part? See drawing below.

I also believe there are similar DreamWear models which Resmed apparently tried to duplicate to make the P30. Perhaps they are better designed.

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 6 days ago Original Poster Sleep Enthusiast

I bought the mask from a local CPAP clinic already assembled and ready to use.

I didn't realize that the cushion contained a covered vent. There is no noticeable air flow in or out of it. It is removable for cleaning but do they mean removable beyond that? I'm hesitant to try to remove the vent cover because it's not clear if it can be replaced although it should be because is has some kind of filter inside it.

The instructions don't mention any function beyond basic assembly although they do state clearly that the mask should not be used unless the device is turned on.

2,314 posts
bio
Was this reply useful? Learn more...
   
[-]
Sierra +0 points · 6 days ago Sleep Patron

The instructions in the manual say to remove the Quiet Air vent cover for cleaning. They say to pay particular attention to the vent holes to make sure they are not plugged. It probably is a good idea to remove the cover and clean it thoroughly. I use an old toothbrush on my P10 which has a fine mesh screen to control the flow out of the vent.

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 5 days ago Original Poster Sleep Enthusiast

That bottom vent doesnt seem to be designed to be disassembled. Can you find anything that indicates that its cover can be removed and reassembled

The vent is as clean as I can get it and the mask works fine while it is under pressure but when the machine is turned off I still cant suck in any air.

If that vent let in even a small amount of air it would negate the vacuum enough to prevent the side tubes from closing completely and that would allow air from above.

I could make adaptations to the mask but why would that be necessary

2,314 posts
bio
Was this reply useful? Learn more...
   
[-]
Sierra +0 points · 5 days ago Sleep Patron
618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 5 days ago Original Poster Sleep Enthusiast

Been there, done that.

It has a filter inside it, perhaps a humidity recycling product of some kind.

The local CPAP clinics all tell me that it can't be disassembled but they also insist that you can't expect to be able to breathe if the machine is turned off,

2,314 posts
bio
Was this reply useful? Learn more...
   
[-]
Sierra +0 points · 4 days ago Sleep Patron

I think once you get that piece out all you can do is clean it with a toothbrush. Can you blow through it to make sure there is a free flow of air through it?

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 4 days ago Original Poster Sleep Enthusiast

I have adapted this mask so that it functions within parameters that I consider essential for survival but the changes I have made are drastic and cannot be discussed or recommended in this forum.

I firmly believe that the AirFit P30 Nasal Pillows mask, in its present configuration, is dangerous and should be recalled.

2,314 posts
bio
Was this reply useful? Learn more...
   
[-]
Sierra +0 points · 4 days ago Sleep Patron

I suspect the reason they have a vent on the top of the head as well as on the nasal piece is to address the issue you have had. They are trying to keep the airflow noise down, and perhaps have over done it with the nasal vent.

618 posts
bio
Was this reply useful? Learn more...
   
[-]
Biguglygremlin +0 points · 4 days ago Original Poster Sleep Enthusiast

I tried two new vents and the airways sucked closed with them too.

The mask needs to be redesigned so that the airways cannot collapse and close off the airflow.

2,314 posts
bio
Was this reply useful? Learn more...
   
[-]
Sierra +0 points · 3 days ago Sleep Patron

I wonder if the nasal style rather than the nasal pillow may be better? It seems to have clear holes for vents rather than the QuietAir vent and perhaps lets the air flow more freely. I believe the nasal pillow part can be switched for the Nasal style without replacing the whole mask.

Please be advised that these posts may contain sensitive material or unsolicited medical advice. MyApnea does not endorse the content of these posts. The information provided on this site is not intended nor recommended as a substitute for advice from a health care professional who has evaluated you.