CCR and laryngospasm

[rddvet]

My wife and I are new to ccr. We both have many years diving oc, nearly all of the last 5 years in caves. In the 25 hours or so that we have been getting used to our units, my wife has had an odd thing happen about 3 times now. She's noted that just out of the blue she gets a sudden tightness in the back of her throat and her description is that it's "hard to breathe through her mouth but at the same time she can inhale through her nose (until the volume in her mask is depleted)." The very first time she thought it may have been a gag reflex because the mouthpiece on her loop is a little larger and bulkier than on oc regs. She's paid attention when it happens and it seems to be a laryngospasm (we both have medical backgrounds). There's a ton of causes for laryngospasm, but dust inhalation can be a cause. When it occurs, she bails out to her bov and it resolves, though she highly suspects it would resolve even staying on the loop. We're thinking that maybe it's a little irritation to sorb dust moving around the loop? We can't really come up with anything else, especially since she says it is very distinctively not a regular gag reflex.
Has anyone heard of or experienced laryngospasm on ccr?

 

[tbone1004]

which CCR?

 

[rddvet]

Fathom

 

[rjack321]

Fathom

@michael-fisch has a similar perhaps best described as hyper sensitivity to sorb dust. Not having see the fathom scrubber I assume it uses a SS screen and not polypro scrims like the JJ? Any chance your could change your filling practices or remove some of the fines?

 

[rddvet]

@michael-fisch has a similar perhaps best described as hyper sensitivity to sorb dust. Not having see the fathom scrubber I assume it uses a SS screen and not polypro scrims like the JJ? Any chance your could change your filling practices or remove some of the fines?

Yes, its the ss screen. She plans to clean her unit and the scrubber really well and then clean the scrubber on a regular basis. I'm not sure how to change how we fill, but would be up for suggestions. We're just doing the classic fill, shake, fill, shake, when it's at the right level, put the top on the scrubber and bang it around to pack it while tightening the top. Since starting on the path of ccrs, we've actually been pretty surprised how much dust is produced by the sorb. We always assumed there was dust, but we're shocked how much comes out in the packing process.

 

[rjack321]

Yes, its the ss screen. She plans to clean her unit and the scrubber really well and then clean the scrubber on a regular basis. I'm not sure how to change how we fill, but would be up for suggestions. We're just doing the classic fill, shake, fill, shake, when it's at the right level, put the top on the scrubber and bang it around to pack it while tightening the top. Since starting on the path of ccrs, we've actually been pretty surprised how much dust is produced by the sorb. We always assumed there was dust, but we're shocked how much comes out in the packing process.

Are you packing outside? I try to open my garage door and pack when there's a slight breeze. You could put a table in the doorway and have a desk fan blowing the dust outside. Pouring from a relatively high height can also allow quite a bit of dust to drift away.

 

[tbone1004]

@rddvet the higher up you can get with the filling the more dust will fly out while you're filling the scrubber.
Also found it packs just as well when you pour the thing full then let it tap down.

Does the inhale counterlung t-piece have a baffle in it? On the meg it does and having one with the baffle may help knock some dust out during inhale by forcing it thru the counterlung

 

[macado]

Are you using Intersorb or Sofnolime? Just curious..I've always found dust varies between kegs but in my observation Intersorb tends to be more dusty than Sofnolime. I've had some really dusty kegs of Sofnolime too so it's not always the case.

When I fill I decant sorb into a smaller 4.5kg container first.. I use a fan that blows sorb dust away and a put funnel into the smaller container. I find that this cuts down on sorb dust considerably. It could help if you think dust is causing the issue.

Also as others suggested, you may want to use an additional filter in your scrubber.

 

[taimen]

Sometimes well into a dive (2 hours+) I find my soft palate getting tired and start unintentionally exhaling through nose. I have been told that this is not uncommon with rebreathers which always have some exhale WOB. Flexing neck , trimming head down and increasing loop volume helps without need to bail out.
Could it be the same phenomenon (palate fatigue due to increased wob and mouth breathing) instead of a real laryngospasm?
@doctormike probably knows this stuff.

 

[sea_ledford]

I was also thinking maybe related to WOB (actually static lung load, not WOB, but that is a different conversation). Not familiar enough with the Fathom to know anything about counterlung placement.

For sorb dust removal, I have heard of people vacuuming the canister once it is packed to get out as much dust as possible.

-Chris