[Equipment] Fabrication of an Enhanced Expiratory Rebreathing Space (EERS)

[sherwoga]

Stupid question as your using the quiet elbow, have you blocked the holes under the diffuser ring as it is unclear from the picture, it looks like you have just blocked the antiaphyixiation  valve

Good observation and yes, you are right.  I blocked the anti asphyxiation holes on the elbow connector.  I noted when I attached the line that I didn't hear/feel the normal thud I hear as pressure builds in the line.  Prior to last night's observation and thinking about your question (not stupid BTW, but very helpful) I didn't understand  that that thud is the check valve closing.  It appears to me when closed that check valve isolates the vents I plugged from the flowing air.  In the event of a pressure loss, the check valve would reopen and create the breathing path directly to the vents I erroneously thought I needed to plug. 

When I woke up this morning I disconnected and reconnected the lines a couple of times making changes in the arrangement of the dead space tube and the straight connector.  I discovered, that in addition to not needing to plug the vents on the elbow connector I also had the straight connector inserted backwards.  I warned readers I would look like I didn't know what I was doing.  I feel a bit foolish to have gotten it so wrong on my first attempt.  And not surprisingly, I didn't get the EERS benefit expected.  Central events were back up, since I put the EPR setting back to 3.  

Tonight's another night.

Thanks for your input.  That is exactly what I was looking for.

[sherwoga]

Color me clueless. Are trying to make yourself re-breathe your carbon dioxide?

The section of tubing that I am attempting to use to create "dead" volume (or re-breathing space) can be considered to be a cylinder of length 6 inch and radius 11 millimeters.  The volume of a cylinder is given as

V = πr²l.

This works out to about 58 mL. 

That should be 1.1 centimeters not 11 milliliters.  Sorry!

[sherwoga]

I've used my EERS apparatus two nights in a row.  The first night was largely a disaster.  I used the arrangement pictured in my original post to this Thread (#1, posted 11-21-2019, 09:06 PM).  The Whisper Swivel valve was in the line backwards. Essentially I had no EERS and since part of the experiment was to turn my EPR on at 3, my central apnea events went back up significantly.  But the experience was somewhat educational. It led me to review more of the helps that are already on the Forum.  In particular, I rediscovered and better understood the example pictured here showing an EERS attached to a Mirage Fx mask.  I had all of the parts to copy that example and assembled them in the same order on my F20 Full Face Mask using the elbow connector that comes with my mask.   I had long distance help from Slowriter, which is very much appreciated. This is what my supply hose looked like after assembly.

   

I started the night with no vents plugged, but thought the amount of air escaping at the Safety valve (located between the two 6-inch sections of Corr-A-Flex Corrugated Tubing) was excessive.  I tried (after my lights were out) to plug the vents on that safety valve by feel.  I completely missed one side.  I discovered I had missed it after a bathroom trip that occurred after 5.5 hours of use (2nd failure).  I corrected the plug position for the rest of the night. 

You might reasonably challenge me as to why I would plug a safety valve.  My intuition was that the valving in my elbow connector located right on my face mask provides the required anti asphyxiation function.  After some further experimentation with the elbow this morning I am convinced of that.  So I am going to use the rest of this post (limited by the number of pictures I can attach) to describe that experimentation.

This picture is a close up of the elbow showing the side vents and the frosted flaps in what I am calling the closed position.  This corresponds to there being no pressure on the entry side of the elbow.

   

For the next picture I plugged the outlet side of the elbow with Mack silicone putty, attached a section of Corr-A-Flex Corrugated Tubing to the inlet side, and blew into the hose to pressurize the line.  Note how the flaps have now moved to plug the side vents.  

   

I conclude that this design makes this elbow into an anti asphyxiation valve.  If, while in use power is lost, the pressure will quickly dissipate and the flaps will move back into the closed position.  That will open a path way directly from my lungs to the vents on the side of the elbow and I won't suffocate! Pretty simple, but very elegant design!!!

So, I believe I can also conclude that I don't need the safety valve I worked so hard yesterday to insert in the supply line as in the first picture above (the one between the two 6-inch sections of Corr-A-Flex Corrugated Tubing).  Discussion on this point is very welcome.  I don't want to do something else dumb.

The Whisper Swivel valve (attached directly to the outlet of the  supply hose from my pump) serves as the vent point so that air from the pump does not sweep the EERS section of tubing.  See my previous posts. So a section of Corr-A-Flex Corrugated Tubing and the Whisper Swivel valve (inserted in the correct direction) should be all I need to fabricate my EERS for use with the F20 Full Face mask.  See my next post.

[SarcasticDave94]

Congrats, a very nice job. This should be in mask parts accessories bins for sale.

[slowriter]

... So a section of Corr-A-Flex Corrugated Tubing and the Whisper Swivel valve (inserted in the correct direction) should be all I need to fabricate my EERS for use with the F20 Full Face mask.

Always is nice when things turn out to be simpler than we first understand, even if we waste some time getting there!

So did you up benefiting from it last night?

[sherwoga]

... So a section of Corr-A-Flex Corrugated Tubing and the Whisper Swivel valve (inserted in the correct direction) should be all I need to fabricate my EERS for use with the F20 Full Face mask.

Always is nice when things turn out to be simpler than we first understand, even if we waste some time getting there!

So did you up benefiting from it last night?

Yes, (pregnant pause) and No.  I still saw a lot of central events (40) and perhaps a few more obstructive events (9) than I would like.  The total time spent in apnea was over 12 minutes   . 

But I think I learned a lot, too.  See my next new reply post where I will share my data from last night, make some observations of my own, and solicit input from the forum. 

In the meantime, thanks for your help yesterday.  I hope what I shared this morning captures enough of our offline discussion from yesterday so as not to deprive other users on the  forum. 

PS.  There is no emoticon for "Pregnant Pause".  Here is what I intend it to mean, since I'm maybe getting a bit too creative:  "A pregnant pause is a pause that builds up suspension in the listener/viewer, for a greater dramatic (especially comic) effect of what follows after the pause."

[slowriter]

I still saw a lot of central events (40) and perhaps a few more obstructive events (9) than I would like. 

If you have it built correctly, might need a longer EERS section?

[sherwoga]

Posting my Data from 2nd night of using my EERS.  Admittedly, the design used and it's implementation was still in a state of flux (see previous post), but I think there is some interesting observations here. 

Some background: 

My AHI numbers have been pretty good, but I've continued to pursue the fabrication of the EERS because I'm still so sleepy throughout most of the day.  Fred Bonjour has repeatedly counseled that I should consider how I feel when considering what to do next. 

I was at a pressure range of 8 to 14 with EPR off prior to my first use of my fabricated EERS.  For both nights of use, I left the pressures unchanged, but turned the EPR on at 3.  I believe the EERS design  was so faulty on the first night as to have had little or no or maybe misleading effect. Regardless I did observe a significant increase in central events and I think that was due to turning the EPR back on.  That conclusion is supported by past experience. 

   

Some observations from the data obtained on 2nd night of EERS use (although still faulty). 

I observe a high number of central events again, but also observe that they are clustered during two periods when the line pressure was at the minimum setting of 8 cm water (not long after turning the system on for each cluster).  I don't know why that should be, but does it suggest that increasing the minimum pressure from 8 to say 10 would help avoid these events?  Some might challenge that this is not really necessary, but the total time spent in Apnea was over 12 minutes.  

The very high leak rate surprised me for both nights.  But I guess in hindsight, it shouldn't.  Purposely putting a hole in the line (a vent) will likely be seen as a leak by the system.  Does this mean that the pump is having to work harder and will using the EERS be hard on the pump?  Also, does it mean that the pressures achieved at the mask are significantly lower than what is being reported?  If so, higher pressures might be in order.  

A cluster of obstructive events did occur as well.  The pump responded by increasing the pressure to the max setting of 14 cm water which in turn drove the leak rate to > 24 L / minute causing OSCAR to declare 50 High Leak Level Events.  Is increasing the maximum pressure an appropriate response?  Doing so should mean the obstructive events will stop more readily, but would also likely exacerbate the high leak level events. 

Finally, I also have the ability to increase the length of the EERS tubing.  What would be the likely impact of doing that on any of these observations or the proposed changes?

I also want to use this post to do some thinking out loud (or in writing) about the way the elbow of the F20 Mask works. In Post #13 of this thread I described how the vent flaps in the elbow work to make the elbow into an anti asphyxiation valve.  I had to use some putty to plug the outlet of the elbow in order to demonstrate how the check valve in the elbow works.  It has dawned on me since that in order for the unaltered supply line to be swept (i.e., the line with no EERS), the sweeping air has to have a place to escape.  A couple more pictures might help.

   

There are two concentric rings and holes labeled in the picture.  I think the holes are the entrance to the exit path for moving air that would sweep the unaltered supply line.  When I used Mack Silicone Putty to plug the outlet end of the Elbow Connector (Post #13), the putty  conformed to both of the two concentric rings.  I haven't devised a way to seal just the outside ring, but it appears to me that the Holes visible between the two rings have to have a purpose.  Absent being able to seal just the outer ring, I don't know how to investigate/prove this.

Now a view from the side of this Elbow Connector. 

   

I believe the space I have labeled "Exit" serves as the normal vent for the sweeping air.  I do not feel air escaping there when in service, but it is well away from my face.  Further I don't hear any whistling of escaping air, but maybe the design is so good that I'm not supposed to.  And is there any merit in using the putty in smaller amounts to block this exit?  Just thinking out loud.  Your input will be appreciated. 

I'm a bit verbose.  If you've read this far, good on ya! Thank you for your interest and input.

[slowriter]

The very high leak rate surprised me for both nights.  But I guess in hindsight, it shouldn't.  Purposely putting a hole in the line (a vent) will likely be seen as a leak by the system.  Does this mean that the pump is having to work harder and will using the EERS be hard on the pump?  Also, does it mean that the pressures achieved at the mask are significantly lower than what is being reported?  If so, higher pressures might be in order.  

On this, I will just say I had no machine-reported leaks when I tried EERS.

[Gideon]

My (bonjour) comments in blue

Posting my Data from 2nd night of using my EERS.  Admittedly, the design used and it's implementation was still in a state of flux (see previous post), but I think there is some interesting observations here. 

Some background: 

My AHI numbers have been pretty good, but I've continued to pursue the fabrication of the EERS because I'm still so sleepy throughout most of the day.  Fred Bonjour has repeatedly counseled that I should consider how I feel when considering what to do next.  and caution since EERS is not in wide use though I know of nothing to be cautious of other than the unknown

I was at a pressure range of 8 to 14 with EPR off prior to my first use of my fabricated EERS.  For both nights of use, I left the pressures unchanged, but turned the EPR on at 3.  I believe the EERS design  was so faulty on the first night as to have had little or no or maybe misleading effect. Regardless I did observe a significant increase in central events and I think that was due to turning the EPR back on.  That conclusion is supported by past experience. 



Some observations from the data obtained on 2nd night of EERS use (although still faulty). 

I observe a high number of central events again, but also observe that they are clustered during two periods when the line pressure was at the minimum setting of 8 cm water (not long after turning the system on for each cluster).  I don't know why that should be, but does it suggest that increasing the minimum pressure from 8 to say 10 would help avoid these events?  Some might challenge that this is not really necessary, but the total time spent in Apnea was over 12 minutes.  Increasing pressure should increase the prevalence of centrals

The very high leak rate surprised me for both nights.  But I guess in hindsight, it shouldn't.  Purposely putting a hole in the line (a vent) will likely be seen as a leak by the system.  Does this mean that the pump is having to work harder and will using the EERS be hard on the pump?  Also, does it mean that the pressures achieved at the mask are significantly lower than what is being reported?  If so, higher pressures might be in order.  Looking at the chart, you are just over the 24lpm threshold, you are still good, the impact of large leaks doesn't magically appear when over 24lpm, it gradually appears.

A cluster of obstructive events did occur as well.  The pump responded by increasing the pressure to the max setting of 14 cm water which in turn drove the leak rate to > 24 L / minute causing OSCAR to declare 50 High Leak Level Events.  Is increasing the maximum pressure an appropriate response?  Doing so should mean the obstructive events will stop more readily, but would also likely exacerbate the high leak level events.  Looking at the chart, you are just over the 24lpm threshold, you are still good, the impact of large leaks doesn't magically appear when over 24lpm, it gradually appears.  Let's see if the Obstructive clusterd persist.  If they do it indicate chin tucking is likely and a cervical collar may be needed.  If that doesn't work then more EPAP may be needed.

Finally, I also have the ability to increase the length of the EERS tubing.  What would be the likely impact of doing that on any of these observations or the proposed changes? An extension/more dead space should decrease Centrals, and have no impact on obstructive apneas.  Possibly require a higher pressure as when switching from a nasal mask to a FFM. EERS from this perspective should act response wise more like a FFM than a nasal or pillow mask because of the added dead space.

I also want to use this post to do some thinking out loud (or in writing) about the way the elbow of the F20 Mask works. In Post #13 of this thread I described how the vent flaps in the elbow work to make the elbow into an anti asphyxiation valve.  I had to use some putty to plug the outlet of the elbow in order to demonstrate how the check valve in the elbow works.  It has dawned on me since that in order for the unaltered supply line to be swept (i.e., the line with no EERS), the sweeping air has to have a place to escape.  A couple more pictures might help.



There are two concentric rings and holes labeled in the picture.  I think the holes are the entrance to the exit path for moving air that would sweep the unaltered supply line.  When I used Mack Silicone Putty to plug the outlet end of the Elbow Connector (Post #13), the putty  conformed to both of the two concentric rings.  I haven't devised a way to seal just the outside ring, but it appears to me that the Holes visible between the two rings have to have a purpose.  Absent being able to seal just the outer ring, I don't know how to investigate/prove this.

Now a view from the side of this Elbow Connector. 



I believe the space I have labeled "Exit" serves as the normal vent for the sweeping air.  I do not feel air escaping there when in service, but it is well away from my face.  Further I don't hear any whistling of escaping air, but maybe the design is so good that I'm not supposed to.  And is there any merit in using the putty in smaller amounts to block this exit?  Just thinking out loud.  Your input will be appreciated. 

I'm a bit verbose.  If you've read this far, good on ya! Thank you for your interest and input.