Quantifying Aerosol Generation in Maxillofacial Trauma Repair Techniques

Study Design Cadaveric simulation study. Objective The novel coronavirus (COVID-19), which can be transmitted via aerosolized viral particles, has directed focus on protection of healthcare workers during procedures involving the upper aerodigestive tract, including maxillofacial trauma repair. This study evaluates particle generation at different distances from open reduction and internal fixation (ORIF) of maxillofacial injuries in the intraoperative setting to reduce the risk of contracting airborne diseases such as COVID-19. Methods Two cadaveric specimens in a simulated operating room underwent ORIF of midface and mandible fractures via intraoral incisions as well as maxillomandibular fixation (MMF) using hybrid arch bars. ORIF was performed with both self-drilling screws and with the use of a power drill for creating guide holes. Real-time aerosol concentration was measured throughout each procedure using 3 particle counters placed 0.45, 1.68, and 3.81 m (1.5, 5.5, and 12.5 feet, respectively) from the operative site. Results There was a significant decrease in particle concentration in all procedures at 1.68 m compared to 0.45 m, but only 2 of the 5 procedures showed further significant decrease in particle concentration when going from 1.68 to 3.81 m from the operative site. There was significantly less particle concentration generated at all distances when using self-drilling techniques compared to power drilling for ORIF. Conclusion Consideration of using self-drilling screwing techniques as well as maintaining physical distancing protocols may decrease risk of transmission of airborne diseases such as COVID-19 while in the intraoperative setting.

A quantitative evaluation of aerosol generation from upper airway suctioning during tracheal intubation and extubation sequences.

Background: Open respiratory suctioning is considered to be an aerosol generating procedure (AGP) and laryngopharyngeal suction, used to clear secretions during anaesthesia, is widely managed as an AGP. It is uncertain whether such upper airway suctioning should be designated an aerosol generating procedure (AGP) because of a lack of both aerosol and epidemiological evidence of risk. Aim: To assess the relative risk of aerosol generation by upper airway suction during tracheal intubation and extubation in anaesthetised patients. Methods: Prospective environmental monitoring study in ultraclean operating theatres to assay aerosol concentration during intubation and extubation sequences including upper airway suctioning for patients undergoing surgery (n=19 patients). An Optical Particle Sizer (particle size 300nm-10μm) was used to sample aerosol 20cm above the mouth of the patient. Baseline recordings (background, tidal breathing and volitional coughs) were followed by intravenous induction of anaesthesia with neuromuscular blockade. Four periods of oropharyngeal suction were performed with a Yankauer sucker: pre-laryngoscopy, post-intubation and pre- and post-extubation. Findings: Aerosol from breathing was reliably detected (65[39-259] particles.L-1 (median[IQR])) above background (4.8[1-7] particles.L-1, p<0.0001 Friedman). The procedure of upper airway suction was associated with much lower average concentrations of aerosol than breathing (6.0[0-12] particles.L-1, P=0.0007) and was indistinguishable from background (P>0.99). The peak aerosol concentration recorded during suctioning (45[30-75] particles.L-1) was much lower than both volitional coughs (1520[600-4363] particles.L-1, p<0.0001, Friedman) and tidal breathing (540[300-1826] particles.L-1, p<0.0001, Friedman). Conclusion: The procedure of upper airway suction during airway management is associated with no higher concentration of aerosol than background and much lower than breathing and coughing. Upper airway suction should not be designated as a high risk AGP.

Outcome of major abdominal surgeries in COVID-19 positive patients with awake anaesthesia: surgeons’ perspective

In view of the COVID-19 pandemic, the use of locoregional anaesthesia has gained popularity as the greatest number of the major abdominal surgical cases which were usually done under general anaesthesia (GA) is now shifted towards awake anaesthesia due to fear of aerosol generation. In a COVID era, with evolving risk of aerosol generation in surgery under GA and the urge for reserving ICU beds for needy patients, this study was undertaken to assess the adequacy of surgery and other benefits with awake anaesthesia. A retrospective observational study for 8 COVID-19 positive patients, undergoing emergency major abdominal surgeries with locoregional anaesthesia in pre-operatively diagnosed COVID positive from May 2020 to May 2021 was conducted. Low to medium risk patients (ASA 1-2) were considered following assessment by anaesthesiologist. We retrospectively analysed data including perioperative events, post-op follow up. The mean operative time was 103 minutes (minimum 50 minutes; maximum 170 minutes). In one case, conversion to general anaesthesia was necessary. Post-operative pain was always well controlled. None of them required postoperative intensive care support. No perioperative major complications (Clavien Dindo ≥3) occurred. Early readmission after surgery never occurred. In our experience in the COVID-19 era, RA may help to limit the intubation-related risk of contagions inside theatres and could be feasible, safe, and painless alternative to GA in selected cases and this approach could become part of an ICU-preserving strategy.

Correction: Lee, B.U. Minimum Sizes of Respiratory Particles Carrying SARS-CoV-2 and the Possibility of Aerosol Generation. Int. J. Environ. Res. Public Health 2020, 17, 6960

The author would like to update a few calculation results in the Abstract and Section 4 “Calculation of Sizes of Respiratory Particles Containing SARS-CoV-2” in the previous publication [...]

Aerosol emission from the respiratory tract: an analysis of aerosol generation from oxygen delivery systems

Introductioncontinuous positive airway pressure (CPAP) and high-flow nasal oxygen (HFNO) provide enhanced oxygen delivery and respiratory support for patients with severe COVID-19. CPAP and HFNO are currently designated as aerosol-generating procedures despite limited high-quality experimental data. We aimed to characterise aerosol emission from HFNO and CPAP and compare with breathing, speaking and coughing.Materials and methodsHealthy volunteers were recruited to breathe, speak and cough in ultra-clean, laminar flow theatres followed by using CPAP and HFNO. Aerosol emission was measured using two discrete methodologies, simultaneously. Hospitalised patients with COVID-19 had cough recorded using the same methodology on the infectious diseases ward.ResultsIn healthy volunteers (n=25 subjects; 531 measures), CPAP (with exhalation port filter) produced less aerosol than breathing, speaking and coughing (even with large >50 L/min face mask leaks). Coughing was associated with the highest aerosol emissions of any recorded activity. HFNO was associated with aerosol emission, however, this was from the machine. Generated particles were small (<1 µm), passing from the machine through the patient and to the detector without coalescence with respiratory aerosol, thereby unlikely to carry viral particles. More aerosol was generated in cough from patients with COVID-19 (n=8) than volunteers.ConclusionsIn healthy volunteers, standard non-humidified CPAP is associated with less aerosol emission than breathing, speaking or coughing. Aerosol emission from the respiratory tract does not appear to be increased by HFNO. Although direct comparisons are complex, cough appears to be the main aerosol-generating risk out of all measured activities.