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Dr Satoshi Akima FRACP 『秋間聰』 Profile picture
@ToshiAkima
May 14 • 9 tweets • 5 min read Twitter logo Read on Twitter
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Repeating warnings from @H_S_E and @NIOSH about earloops having a low fit test pass rate is unpopular, but what does the published literature say about earloop KN95s? #KN95
One study found that “KN95 masks failed fit testing in all (82 out of 82, 100%) healthcare workers evaluated”. openres.ersjournals.com/content/6/4/00…
Another study of #KF95 mаsks found that: “A result of ‘failed’ was recorded for 39 of 42 fit test episodes”. ijic.info/article/downlo… ImageImage
Another study showed KN95s had an average fit factor of 2.2 out of the 100 points needed to pass. journals.plos.org/plosone/articl… Image
When headstrap Ν95s were modified to take earloops (ELSS), the Fit Factor scores immediately dropped, causing wearers to fail (but improved with a novel fitting system, NFS). The Aura 1860+ dropped from an FF of 161.6 ± 46.9 to less than half of that. academic.oup.com/annweh/article… Image
The last paper shows that even if you get a lucky freak pass on an earloop respirator, your FF score will be bettered by an equivalent headstrap respirator. It really is true that headstraps respirators are generally better.
And no, I know nothing about the novel faceseal system. I can't find anything on it being for sale. If you added it to the headstraps I imagine it would improve the fit factor there too. isrp.com/the-isrp-journ… Image
This table is really quite depressing. Going from headstraps to earloops more than halved the Fit Factor. That's double the inward leakage. It's just not worth it. Image
Look at this study again. That's a 92.85% failure rate for KN95s, despite subjects being allowed to tweak their mаsks to improve the fit. Even if you belong among the 8% who pass, you shouldn't be recommending them to the 92% who don't, as you'll condemn them to be infected. Image

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More from @ToshiAkima

Dr Satoshi Akima FRACP 『秋間聰』 Profile picture
May 14
Just a brief heads up for AU and NZ readers. Some Shigematsu respirators are now available with AS/NZS 1716: 2012 approvals (but not ATRG for official HCW use). I just tried out the RX01 and pass a fit test. Image
It has a speech diaphragm but it results in a slightly metallic voice quality. The exhalation valve is the biggest I've ever seen, resulting in minimum resistance. Fit is similar to 3M elastomerics. Use the following size chart. Image
Note that the filters are sold individually not by the pair. For CV19 aerosol mitigation you only need the particulate filters: SHIGEMATSU 05STS030 - P3R Filter (each). Image
Read 8 tweets
Dr Satoshi Akima FRACP 『秋間聰』 Profile picture
May 14
Just a passing observation on the @3M 1860+. Staff fit tested to the 3M 1860/1860S Ν95 cupped models seem to have fuller face shapes (face on the left) with a smaller jaw. Thinner/oval face (right) shapes seem to match better to the Aura (or Trident). 🧵 Image
You see this on @3M promo shots as well, like the face on the 1860+ box. He looks like a team member who did a rotation with my team and who wore the 1860+ for a term without contracting C19. Image
Another example of a promo shot for the 3M 1860+ with a fuller face that fits this pattern. Image
Read 8 tweets
Dr Satoshi Akima FRACP 『秋間聰』 Profile picture
May 6
It's time for me to come out of the closet and declare myself an anti-màsker. Get rid of màsks! Wear respirators instead. Join me, and with our combined strength, we can end this destructive conflict [PAPR respirator hisses].😉 🧵 Image
It's official. Màsks are a droplet/splash precaution. You need respirators to protect you against aerosol or particulate inhalation. Nikki McCullough of 3M explains this well-established distinction well.
You can get models that are both a respirator-AND-surgical-màsk rolled into one. The 3M Aura 1870+ N95 has aerosol/particulate filtration capacity as well as surgical splash proofing. 3m.com/3M/en_US/p/d/v… Image
Read 15 tweets
Dr Satoshi Akima FRACP 『秋間聰』 Profile picture
May 6
I think this is a nice start, but I would emphasise that most science does not use RCTs. The device you are reading this thread on has not been tested by RCT, any more than an aeroplane or bridge. Yet, you wouldn't question whether they work when your life depends on it. 🧵
The majority of science is conducted without being reduced to the crude empiricism of RCTs. That's because the best theoretical models (eg relativity theory) have a lot of predictive power and predictions can be confirmed by direct measurement.
In biological systems, theoretical models do not have as much predictive validity, and direct corroborative measurement of predictive parameters is more difficult to undertake. This reduces us to crude empirical live testing, akin to crash testing with live subjects. Image
Read 5 tweets
Dr Satoshi Akima FRACP 『秋間聰』 Profile picture
Apr 23
A review of the @uvexsafetygroup Megasonic oversized safety goggles. Improves your respirator's fit by pressing down on the nose wire. Great visibility. Image
On some models of 3M Aura, such as the 1862+ model worn here, the straps are a little loose, allowing minor leakage at the nose. A fit test (FT-10 QLFT) was repeated, wearing the Megasonics clamping down over the top of the nose wire. It stopped the leakage completely. Image
What this shows is that oversized goggles can improve the fit, but only if the nosewire is the point of weakness. If the leakage is at the chin area or at the sides (as on surgicals and KF94s), it will do nothing. This is NOT a substitute for a fit test! Get fit tested, please.
Read 13 tweets
Dr Satoshi Akima FRACP 『秋間聰』 Profile picture
Apr 22
I was looking at the 3M Germany website when I was reminded of the fact that the German word for personal protective equipment is “persönliche Schutzausrüstung”. If you look up the word “Rüstung” on Google, this is what you get. It literally means “armour”. 🧵 ImageImage
It's a reminder that the physics underlying how a medical bioaerosol filter works is the same as that in a military tactical respirator used in biological warfare. This is war.
You'll be prying the “Schutzausrüstung” off my dead body.😡 ImageImage
Read 4 tweets

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