2. DEFINE AEROSOLIZATION AND DROPLETS
The exact definition (size of particles) is debated heavily
General Definition: In general, aerosols are liquid or solid particles suspended in air. They can be visible, like
fog, but are most often invisible, like dust or pollen.
Divided into “small” droplets and “large Droplets
Most consider true aerosols to be “small: droplets
There is probably some gray area and overlap between the two.
Disease transmission through large droplets is what we often refer to as “droplet/contact spread”
Small Droplet aerosols are so small that buoyant forces overcome gravity, allowing them to say suspended in
the air for long(er) periods until they evaporate or hit the floor.
True “airborne” transmission occurs if very small aerosols evaporate into dried desiccated viral “nuclei” but this
is uncommon compared to aerosols.
3. WHAT SOME STUDIES TELL US
Aerosolized and droplets are a significant mode of infection for healthcare workers
Layered use of PPE (especially masks) by providers significantly reduces the risk.
“…We found a near 80% reduction in risk for infection for nurses who consistently wore masks
(either surgical or N95). This finding is similar to that of Seto and colleagues, who found that both
surgical masks and N95 masks were protective against SARS among healthcare workers in Hong
Kong hospitals . When we compared use of N95 to use of surgical masks, the relative SARS risk
associated with the N95 mask was half that for the surgical mask”
Loeb, M., McGeer, A., Henry, B., Ofner, M., Rose, D., Hlywka, T., Levie, J., McQueen, J., Smith, S., Moss, L., Smith, A.,
Green, K., & Walter, S. D. (2004). SARS among Critical Care Nurses, Toronto. Emerging Infectious Diseases, 10(2), 251–
255. https://doi.org/10.3201/eid1002.030838
4. WHY IS THIS
IMPORTANT?
Understanding droplets
helps us understand what
strategies will he helpful to
mitigate risk.
The only way to bring the
risk to nearly 0% is to walk
around in a Level A HazMAT
Suit, but the risk can be
reduced dramatically with
simple measures.
This Photo by Unknown Author is licensed under CC BY-SA
6. WHY ARE WE JUST NOW CONCERNED
ABOUT THIS?
Other countries have been concerned
about this since the 2009-2012 SARS
epidemic
Canada in particular has some
specific guidelines for EMS
America…. Well….yeah
8. COUGHING
This is actual optical
spectrometry of a forced
cough downward showing
several feet of spread in a
fraction of a second. Up to 2
liters can expelled in a second
or two of forceful coughing.
A schlieren optical study of the human cough with and without
wearing masks for aerosol infection control, Volume: 6, Issue:
suppl_6, Pages: S727-S736, DOI:
(10.1098/rsif.2009.0295.focus)
11. EFFECT OF A
MASK ON A
PATIENT WHO IS
SUPINE
(I.E. ON A COT)
STILL
BENEFICIAL
12. WHY APPLY A MASK OF ANY TYPE?
Up to two liters of air and droplets can be expelled during a forceful coughing episode.
Neither the surgical nor the N95 mask has any possibility of passing or containing all of
the 2 l or so of air expelled in a few seconds during a cough.
Thus, leakage around the mask or filtering through the mask must occur,
The benefit from applying a mask is to the patient is:
“Source Capture” of droplets through the mask
Decreasing the “cloud” of droplets by decreasing the velocity and direction of air escaping the mask.
A schlieren optical study of the human cough with and without
wearing masks for aerosol infection control, Volume: 6, Issue:
suppl_6, Pages: S727-S736, DOI:
(10.1098/rsif.2009.0295.focus)
13. THE BENEFIT OF FITTING A MASK ON THE PATIENT
Wearing any mask is better than no mask
from a “source Capture” perspective.
Wearing a fitted mask of any type (i.e.
pinched at the nose, etc) forced expelled air
through the mask ,where droplets and
possibly the virus (depending on the mask)
may be trapped or filtered.
A schlieren optical study of the human cough with and without
wearing masks for aerosol infection control, Volume: 6, Issue:
suppl_6, Pages: S727-S736, DOI:
(10.1098/rsif.2009.0295.focus)
15. KEY THINGS TO REMEMBER MOVING FOWARD
Blatantly pirated from a April 6, 2020 “First 10 EM” post:
All of the available evidence is an incredibly low level, with a high risk of bias.
Some of these procedures are almost impossible to separate retrospectively. Did the provider get infected while
intubating or suctioning the patient? Was it the CPR or use of a BVM? The data is simply not good enough to
make such granular distinctions.
Severity of illness is an important confounder. Patients placed on noninvasive ventilation are likely to be sicker
and therefore also likely to have much higher viral loads. Simply avoiding noninvasive ventilation will not lower
their viral load and therefore may not reduce risk.
Much of the basic science research focuses on the distance that exhalations make it from the patient, using
smoke or water vapor to visualize the breath. As was discussed previously, COUGHING and SNEEZING spreads
droplets farther.
Important distinction between the physical production of aerosols and the risk of transmission of disease.
Some procedures might produce more aerosols, but not put healthcare workers at higher risk. Conversely,
procedures might not actually produce airborne aerosols, but could still represent very high risks of disease
transmission to healthcare workers.
Morgenstern, J. (2020, April 6). Aerosol generating
procedures. First10EM. https://first10em.com/aerosol-
generating-procedures/
16. WHAT ARE AEROSOL GENERATING PROCEDURES?
Medical procedures that have the potential to create aerosols in addition to those
that patients regularly form from breathing, coughing, sneezing, or talking are
called AGPs.
While there are many suspected AGPs, few AGPs were confirmed to generate
aerosols.
This is different from Droplet generating procedures and the risk of direct contact.
Many procedures generate both Droplets AND aerosols, and it is hard to
distinguish.
17. DROPLETS AND
AEROSOLS
Large Droplets:
Do not travel far
Pathogens tend to survive
longer
Smaller Droplets
Travel farther
Pathogens tend to not
survive as long
Certain respiratory viruses,
like influenza and
Coronavirus, are believed to
transmit between people by
both small and large
droplets.
18.
19. DROPLETS AND AEROSOLS
Certain AGPs generate either small or large droplets, or both.
AGPs could potentially amplify a normal route of transmission for respiratory
viruses or open a new route of transmission for other viruses.
Example, EBOV (Ebola) would not normally be spread by coughing because it is not found in the
respiratory track in large quantities, but AGMPs could aerosolize EBOV, making it more
transmissible.
Two broad categories of AGPs
Procedures that mechanically create and disperse aerosolized pathogens
Procedures that cause the patient to cough, which spreads the pathogen in expelled air
20.
21. SOME OTHER
EXAMPLES
Tracheotomy was associated with
SARS-CoV transmission in one case
(but did the patient cough? We do not
know)
Surgical power tools aerosolizing
Manipulating BiPAP/CPAP masks
Vomiting
Feces and flushing of toilets
(particularly those with out lids)
This Photo by Unknown Author is licensed under CC BY-NC-ND
22. STANDARD OXYGEN THERAPY
Nasal Cannula at small to normal rates (< 6 LPM)
Higher the flow, the farther the spread
Droplets spread to about 0.3-0.5 Meters (1 - 2.5 Feet)
Coughing increased the spread
Surprisingly, High Flow NC did not seem to increase the spread in influenza /pneumonia patients, but was
comparable to a NRB.
Simple and Non Rebreather mask
Higher the flow, the farther the spread
Comparable to NC based on Flow
Coughing increased the spread
Droplets spread to about 0.3-0.5 Meters ( 1-2.5 Feet)
Nebulized medications with Jet Nebulizer (like our nebs)
Depends on how sick the lungs are- The sicker the lungs the less medication was inhaled and the more was exhaled /escaped into the
environment
0.5 M (1.5 feet) to 0.8 Meters (2.4 feet)
Coughing increased the spread
Mask Nebulization reduces the spread
23. RECOMMENDATION: PUT A MASK OVER THE NRB OR THE NC!
Surgical Mask Over a NC Surgical Mask over a NRB
24. BVM/NIPPV AND CPR
Using a BVM or performing CPR seems to produce large droplets
Shorter distance
Longer duration virus can survive
“Risk area” of about 1 meter (3 feet)
Using a Nebulizer seems to produce small/medium droplets
Longer Distance
Shorter duration
Some small droplets remained “airborne” for about 20 minutes. Emphasizes the importance of airing out the ambulance after
transport.
Simonds, A., Hanak, A., Chatwin, M., Morrell, M., Hall, A., Parker, K., Tweedy, J., & Dickinson, R. (2010). Evaluation of
droplet dispersion during non-invasive ventilation, oxygen therapy, nebuliser treatment and chest physiotherapy in
clinical practice: Implications for management of pandemic influenza and other airborne infections. Health
Technology Assessment (Winchester, England), 14, 131–172. https://doi.org/10.3310/hta14460-02
25. ESTIMATED RISK WITHOUT PPE (PPE REDUCES RISK)
Tracheal Intubation 39.6-61.4 %
Suctioning before intubation
5932%
Suctioning after intubation 28.8%
Nebulizer Treatment 73.1%
Oxygen Mask manipulation 64%
Chest Compressions 27.3%
Chest compression produces cough
like plume
Defibrillation 55.3%
Chest contraction produces cough
like plume
Tran, K., Cimon, K., Severn, M., Pessoa-Silva, C. L., & Conly, J. (2012). Aerosol Generating Procedures and Risk of
Transmission of Acute Respiratory Infections to Healthcare Workers: A Systematic Review. PLoS ONE, 7(4).
https://doi.org/10.1371/journal.pone.0035797
27. WHAT ABOUT ADVANCED AIRWAY MANAGEMENT? LMA
OR ETT?
From the AHA (April, 2020 update):
“…While the procedure of intubation carries a high risk of
aerosolization, if the patient is intubated with a cuffed endotracheal
tube and connected to a ventilator with a high efficiency particulate
air (HEPA) filter in the path of exhaled gas and an in-line suction
catheter, the resulting closed circuit carries a lower risk of
aerosolization than any other form of positive-pressure ventilation.”
30. CPR AS AN AEROSOLIZATION METHOD
Believed to be “large Droplet” risk (1 meter)
Some have recommended using a NRB instead of a mask but
this does not seem to reduce the risk.
To make a NRB useful during CPR you have to run it at “flush” or
very high rates. This increases the risk, not reduces it.
Use of a CONTINOUS 2-HANDED E-C or T-E face mask seal with
a HEPA Filter is the most effective way to reduce droplet
transmission as this reduce the risk of aerosolizing droplets (big
and small) by “capturing” droplets and forcing them through the
HEPA filter on exhalation.
Weingart, S. (2020, March 27). COVID Airway Management
Thoughts. EMCrit Project. https://emcrit.org/emcrit/covid-
airway-management/
34. DOES ETCO2 SAMPLING “AEROSOLIZE”
In short… NO.
There is a concern that an ETCO2 device may be cross-contaminated, or that the
sampling process will aerosolize pathogens.
The World Health Organization (WHO) and Center for Disease Control (CDC) have
recommended the use of an N95 filtering facepiece respirator (FFR) as best
practice for health care workers. The N95 FFR contains a 0.3 micron filter, which
provides filtering out all types of particles, including bacteria and viruses.
·The Micostream™ FilterLine® sampling line contains a 0.2 micron sterilizing-grade
filter designed to reduce risk of biohazard contamination of the monitor. As this
filter exceeds the recommended 0.3 micron filter used in the recommended
personal protective equipment (PPE), it is believed that there is not a risk to the
monitor/defibrillator and no risk of aerosolization from sampling.
Providers should be careful attaching and removing ETCO2 however.
·Some customers have been placing a Heat and Moister Exchanger with Filter
(HMEF) or High Efficiency Particulate (HEPA) filter in the circuit between the device
and the EtCO2 FilterLine
They may experience some mild distortion of the waveform, but should still be able
to obtain clinically relevant information (waveform and numerical values).
