Everytime we intubate someone we aerosolize the virus. A virus that now is floating in the air and can be easily inhaled. No longer just a "droplet" to be shielded away. Recent published work in anesthesiology is suggesting that intubation is extremely high risk for the intubator; and requires a lot of PPE (that most hospitals no longer have steady access to: gowns, gloves, N95, goggles, and full head hood!
Intubation with a tent -- shows distribution of particles aerosolized
(courtesy of UC David Sim Fellow James Delgadillo)
I can't think of an obvious mechanism for aerosolization in a paralyzed person when you manipulate just the airway and move very little physical mass (the ET tube) into a fixed space -- some air flows out but not much and we aren't bagging or doing chest compressions so the air should be stagnant. Some research seems to suggest the particles are aerosolized in inhalation; and released during exhalation -- and 30-40 seconds after giving a paralytic might be the PEAK moment airflow out of the lungs occurs passively from elastic recoil in end-exhalation -- i've never seen an EMG of the diaphragm over time with a paralytic (but i remember being taught the diaphragm is last to go)
There is some lit on relative risks with procedures, but no clear mechanism of how it happens. They make the assumption that these events aerosolized (without fully explaining why they assume that)
It's all SARS data; but clustering the data in a baby meta analysis seems to suggest a 6x risk of transmission with intubation. Bipap follows close behind w/ O2 mask manipulation. Hard to sort out from their pile of odds ratios which tasks are more "aerosolizing" vs more "droplet spraying"
You could compare RSI intubations vs anesthesia intubations (at cornell they rarely do RSI, at least on my anesthesia rotation they rarely did) -- they were doing the vast majority of covid intubations at Cornell. 4 of them stood next to me for over an hour debating how and when to intubate a COVID pt; and setup for over 30 minutes. That might help differentiate the mechanism (prep and PPE) -- but you would have to do it after then pandemic is over and see which providers got sick and what type of intubations they did. If enough of them are doing non RSI it might be powered enough for that idea.
One experimental study (looking at particles generated inhalation/exhalation) thinks it's from ruptured fluid films during inhalation and just moves up the tract with exhalation; but experimentally disagrees with assumption that its turbulent flow through airways (as demonstrated by less particles when quickly breathing out). Deep exhalation seems to be the biggest risk in concentration generation. Perhaps recruitment events increase this (so PEEP drives more fluid rupture); or simply relaxing the diaphragm fully with paralysis generates a giant surge of particles (RSI does it). This fits with the theory that most particles are coming out after the diagram is paralyzed.
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