1.2 Smaller particles
The aerosolisation of smaller particles (≤10μm) was considered by six
studies19-24. An optical particle counter (OPC) was
used by the majority,19-23 permitting detection of
such particles and assessing their number, concentration, and size.
Using an OPC capable of detecting particles 1.0-10.0μm (OPS 3330; TSI
Inc., USA), Workman et al. (2020b)19 analysed
aerosolisation following cold steel instrumentation, electrocautery and
use of the microdebrider and high-speed drill in a cadaveric setting.
Readings were taken with 30 second periods of activity. Significant
particles were detected following electrocautery and high-speed drill
application to the sphenoid rostrum but no particles were detected with
either cold steel instrumentation or microdebrider use. A further study
from the same group also detected particles <10μm in size
following endonasal high-speed drill use.20
Later work by Sharma et al. (2021a)21 also utilised an
OPC but considered even smaller particles, ranging 0.3-10μm (OPS 3330;
TSI Inc., USA). In a similar cadaveric study to that of Workman et al.
(2020b)19 above, they performed cold steel
instrumentation, electrocautery and tested use of the microdebrider,
high-speed drill and ultrasonic aspirator. In contrast, they found that
all procedures produced significant increases in particles
<10μm compared to baseline, noting that most particles were
<1μm, explaining the disparity between their work and that of
Workman et al. (2020b). Sharma et al. (2021a)21 also
showed significant differences in particle detection between procedures,
with the use of the high-speed drill generating the most and powered
endoscopic sinus surgery simulations the least. That the use of the
microdebrider during these simulations generated lower levels of
aerosols than cold instrumentation could also be linked to the role of
suction within the microdebrider device.
Although OPC technology allows quantification of particles
<10μm, it does not consider their aerodynamic properties. The
use of a cascade impactor allows for not only particle detection but
also an assessment as to their momentum, based on density and speed.
Such results are arguably more useful in measuring risk of
aerosolisation than those captured by OPC alone and, based on this,
Dharmarajan et al. (2020)24 performed cadaveric
simulations with cascade impactor (Next Generation Impactor; Copley
Scientific, UK) and fluorescent tracer. In keeping with similar work,
they demonstrated production of particles <3.30μm after
endonasal drilling but, using riboflavin as a tracer, were able to
filter results to confirm that particles detected were fluorescent and
so from the drilled surface.
Moving from simulation studies to those with patients, Murr et al.
(2020)22 analysed particle detection during five
endonasal procedures taking serial OPC readings at the position of the
surgeon, scrub practitioner and anaesthetist. Significant increases in
particles 0.3-10μm were measured with microdebrider and drill use but
not for cold instrumentation. Sharma et al. (2021b)23analysed nine endonasal surgeries and mapped to a log of intraoperative
steps, with specific attention to use of the microdebrider, drill and
coblator. Results showed spikes in particles between 0.3-10μm during
sinus surgery (including during cold instrumentation) and skull base
surgery (during electrocautery and coblation). Results failed to show
detectable spikes during high-speed drill use, contrasting with all
other studies considering this activity. The reasons for this remain
unclear but could reflect limitations in sample size, given such
clinical work to date has been small in scale and experimental studies,
though more numerous, also remain limited in the number of simulations
performed.