key: cord-0759969-k4x2pfre authors: Leong, Samuel C.; Mogre, Dilesh; Andrews, Peter; Davies, Elgan title: Reducing the risks of endoscopic sinonasal surgery in the Covid‐19 era date: 2021-03-10 journal: Clin Otolaryngol DOI: 10.1111/coa.13743 sha: 24e1b50239a2141a6b76939288a6f81d1f442167 doc_id: 759969 cord_uid: k4x2pfre OBJECTIVES: Many routine sinonasal procedures utilising powered instruments are regarded as aerosol‐generating. This study aimed to assess how different instrument settings affect detectable droplet spread and patterns of aerosolised droplet spread during simulated sinonasal surgery in order to identify mitigation strategies. DESIGN: Simulation series using three‐dimensional (3‐D) printed sinonasal model. Fluorescein droplet spread was assessed following microdebriding and drilling of fluorescein‐soaked grapes and bones, respectively. SETTING: University dry lab. PARTICIPANTS: 3‐D printed sinonasal model. MAIN OUTCOME MEASURES: Patterns of aerosolised droplet spread. RESULTS AND CONCLUSION: There were no observed fluorescein droplets or splatter in the measured surgical field after microdebridement of nasal polyps at aspecific irrigation rate and suction pressure. Activation of the microdebrider in the presence of excess fluid in the nasal cavity (reduced or blocked suction pressure, excessive irrigation fluid or bleeding) resulted in detectable droplet spread. Drilling with either coarse diamond or cutting burs resulted in detectable droplets and greater spread was observed when drilling within the anterior nasal cavity. High‐speed drilling is a high‐risk AGP but the addition of suction using a third hand technique reduces detectable droplet spread outside the nasal cavity. Using the instrument outside the nasal cavity inadvertently, or when unblocking, produces greater droplet spread and requires more caution. The risk of transmitting respiratory viruses during aerosol-generating procedures (AGPs) of the respiratory tract is high. Powered instruments typically used during ENT procedures, such as intranasal microdebriding or mastoid drilling, have been identified as AGPs although the actual risk of transmitting viral particles remains uncertain. 1 Prior to the Covid-19 pandemic and subsequent reported deaths of surgeons contracting coronavirus from infected patients, the risk of aerosolised virus transmission was recognised but not considered to be as dangerous. This realisation resulted in temporary cessation of elective surgery, including all routine ENT procedures. 2, 3 The current recommendations for personal protective equipment (PPE) required to undertake AGPs continue to evolve as new epidemiologic and scientific evidence become available, influenced by external factors such as socio-economic pressures, supply chain issues and advice from medical professional associations. Recent studies, prompted by the Covid-19 pandemic, have demonstrated that many powered instruments used in sinonasal surgery are aerosol-generating with high-speed drilling producing the greatest potential. [4] [5] [6] Whilst previous studies have described the patterns of aerosolised droplet spread during simulated endoscopic sinonasal surgery, the aim of this study was to assess how different instrument settings would affect detectable droplet spread. The ability to vary instrument settings mimics real-life conditions where surgeons may have personal preferences or may choose to alter settings to better suit the clinicopathological requirement. It is envisaged that the results of this study will inform how best to mitigate droplet spread, evaluate choice of instruments and consider droplet spread as site dependent within the sinonasal cavity. The study protocol was approved by the Research Governance and Ethics Office of the Liverpool School of Tropical Medicine (Research Protocol 20-046). All simulated surgical procedures were undertaken in a dry laboratory on a realistic, life-sized model (3D LifePrints UK Ltd. Liverpool, U.K.) derived from open-sourced CT scan data (OsiriX. Pixmeo SARL. Bernex, Switzerland). The 3-D printed model was placed in a supine, 30° head-up position on a medical examination bench covered by an impervious black sheet ( Figure 1A) . A grid pattern on the sheet followed the design described in a recently published study 4 . The model was placed at the apex of a triangle extending to the edges of the sheet at a 50° angle, with the sides of the triangle extending from the model measuring 55 cm to the edge of the sheet. Subdivisions were made, with the central portion of the first subdivisions positioned 6 cm away from the nasal aperture, and each subsequent subdivision at 12-cm intervals. Sections closer to the nares were divided into smaller subdivisions. Each subdivision was at least 10 cm in maximum diameter. The procedures include: was added to the irrigation fluid; 1 g dye diluted in 250 mL irrigation fluid. Various irrigation rates, oscillation speeds and suction pressure settings were tested (Table 1) . With each combination of settings, the microdebrider was activated for one minute and the presence of fluorescein-dyed irrigation fluid drips and droplets from the instrument tip were assessed in the darkened laboratory room aided by UV lighting ( Figure 1B ). (1 mg in 25 mL) were used to simulate nasal polyps. Endonasal surgery was performed using a 4 mm 0° endoscope connected to monitor and camera system (Karl Storz). At the start of each experiment, pieces of grape were placed in the nasal cavity and middle meatus of the model before microdebriding for one minute ( Figure 1C ). The black sheet was then inspected for fluorescein droplets using the UV lamp ( Figure 1D ,E). The microdebrider was unblocked with the supplied cleaning brush stylet when required. Remnants of the grapes were removed from the model and replaced with fresh pieces prior to the next experiment. The model and surrounding surgical field were then cleaned and rechecked with the UV lamp before commencing the next experiment. Each was repeated four times to provide five sets of data. The assessment of dripping from the instrument tip during external activation of the microdebrider was undertaken in binary fashion, that is present or not present ( Figure 1B) . Similarly, the presence of droplet deposition on the surgical field following intranasal activation of the microdebrider or drill was determined in a binary fashion ( Figure 1D ,E). As each experiment had a total of five data sets, the results were aggregated into a heat map to illustrate the frequency of droplet detection; 0 = black, 1-2 = yellow, 3-4 = orange and 5 = red. During external activation of the microdebrider at 2000 rpm (oscillation mode), dripping from the instrument tip occurred as the irrigation rate was increased incrementally while suction pressure was fixed ( Table 1 ). Higher irrigation rates required higher suction pressures to stop dripping. Expectantly, dripping from the microdebrider tip occurred when suction was switched off and when the irrigation rate was increased to 40 mL/min despite having maximum suction pressure (240 mmHg). With the irrigation rate fixed at 25 ml/min, no dripping was observed during oscillation at 5000 rpm with suction pressure set at 140 mmHg and above. When the microdebrider was switched to forward mode (e.g. to simulate shaving turbinate bone during turbinoplasty) and 25 mL/min irrigation maintained, no dripping was observed at all suction pressure settings. However, at 40 mL/min irrigation, dripping was observed even at the highest suction pressure setting. Microdebrider. Oscillation mode, 2000 rpm Although diamond and cutting burs have built-in irrigation, only the former have a suction evacuation port. Drilling with the cutting burs resulted in greater and wider spread of droplets on the detection grid than with the diamond bur ( Figures 3A-F and 4A-D) . Regardless of bur type, drilling on the sphenoid rostrum resulted in less droplet detection compared to drilling within the anterior nasal cavity. The introduction of an additional suction tube resulted in no droplet detected on the grid when the sphenoid rostrum was drilled with the diamond bur ( Figure 3F ). At this setting, no dripping was observed outside the nasal cavity (Table 1 ) and no detectable droplets were observed when nasal polyps were debrided ( Figure 2B ). However, droplets were detected when the suction pressure was reduced to 100 mmHg Unlike recent studies where cadavers were utilised in the experiments, we decided to use a realistic 3-D printed model because we wanted to simulate common sinonasal procedures such as nasal polypectomy and be able to replicate the experiments consistently whilst observing trends in results. We also believed that fluorescein- This study has focused on instruments designed by one manufac- The addition of a third hand suction device when drilling the sphenoid rostrum resulted in no detectable splatter of droplets ( Figure 3F ). The coarse diamond bur used in our experiment had a built-in suction port at the tip of the round bur and endonasal drilling should be performed using the sides of the bur rather than the tip. Dharmajan et al also concluded that placement of an additional suction in the nasal cavity or nasopharynx whilst drilling resulted in complete elimination of all detectable aerosols by a high-fidelity particle counter. 11 It is important to note, however, that the risk of AGP remains and in no way obviates the need for appropriate PPE. In another study which utilised an endoscopy mask connected to a suction unit operating at 200 mmHg, there was significant reduction in fine particulate production and droplet spread during simulated sinus surgery. 12 The aim of this study has not been to eliminate the AGP potential of powered instruments, but rather to provide greater understanding of an issue poorly evaluated prior to the Covid-19 pandemic and offer mitigation strategies to optimise safer surgery. Surgeons undertaking endoscopic sinus surgery should be aware of the technical parameters of the various powered instruments they use, as well as being able to alter settings and troubleshoot when necessary. Activation of the microdebrider or drill bur should not occur outside the nasal cavity, especially after the instrument has been used in the patient. Clear understanding of the interactions between irrigation rates and suction pressures when using a microdebrider or drill provide additional information to reduce and minimise aerosol production during sinonasal surgery. It should be noted that data presented in this study focused on instruments manufactured by one company (Medtronic Inc.) and therefore should not be extrapolated to other manufacturer's microdebriders or drills without validation. This is because bur designs and instrument performance settings differ between various manufacturers. The placement of an additional suction catheter during endonasal drilling, either held by an assistant (three hand technique) or placed in the vicinity of the surgical field, reduces droplet spread. 4,10,12,13 Understanding the relationship between irrigation rates and suction pressures whilst using a microdebrider allows a strategy to reduce droplet production and potential aerosolisation during powered sinus surgery. Activation of the microdebrider when there is fluid accumulation in the nasal cavity has been demonstrated to cause droplet contamination, similarly outside the nose when unblocking. High-speed drilling is a high-risk AGP, but the addition of suction (two surgeon, three-hand technique) reduces detectable droplet contamination outside the nasal cavity. The study protocol was approved by the Research Governance and Ethics Office of the Liverpool School of Tropical Medicine (Research Protocol 20-046). None. SCL, PA and ED conceptualised the study. SCL, DM and ED undertook the experiments. All authors contributed to the data analysis, drafting and final review of the manuscript. Due to the nature of this research, data sharing is not applicable to this article. Samuel C. Leong https://orcid.org/0000-0002-7213-0387 Dilesh Mogre https://orcid.org/0000-0001-5434-1917 Aerosol-generating otolaryngology procedures and the need for enhanced PPE during the COVID-19 pandemic: a literature review Guidance for ENT during the COVID-19 pandemic Aerosol-generating procedures in ENT Endonasal instrumentation and aerosolization risk in the era of COVID-19: simulation, literature review, and proposed mitigation strategies Cadaveric simulation of endoscopic endonasal procedures: analysis of droplet splatter patterns during the COVID-19 pandemic Mitigation of Aerosols Generated During Rhinologic Surgery: A Pandemic-Era Cadaveric Simulation. 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