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.