Airborne Aerosolized Mouse Cytomegalovirus From Common Otolaryngology Procedures: Implications for COVID-19 Infection

Aerosol mitigation in upper airway surgery

BACKGROUND

Aerosol generating procedures pose a risk for SARS-CoV-2 transmission, and comprise a large percentage of cases performed in otolaryngology. An optimal method to mitigate this hazard does not currently exist. This study examined methods to mitigate surgical aerosols from the operating room.

METHODS

Utilizing an intubation manikin (Nasco Healthcare) and particle counter (Sensirion SPS30), a series of electrocautery-induced aerosols containing particles 0.5-10 μm in diameter were measured. Three different mitigation strategies were tested: intraoral (Yankauer, suction Bovie pencil (SBP)), extraoral (smoke evacuator system (SES)), and their combinations.

RESULTS

SES was effective compared to controls, but inferior to intraoral mitigation strategies (p < 0.0001). Combining SES with any intraoral mitigation strategy did not enhance mitigation efficiency, and in some comparisons led to inferior performance (SBP vs SBP-SES, p < 0.05). Comparison of intraoral mitigation strategies found no statistically significant differences between techniques, although SBP was found to have the lowest overall level of particles.

CONCLUSIONS

Intraoral suction techniques are recommended for aerosol mitigation. Extraoral SES use alone is insufficient for aerosol mitigation, and may be counterproductive when used with intraoral suction techniques. Further research is needed to determine the optimal mitigation strategy for intraoperative surgical aerosols.

Variation in aerosol generation by surgical modality during oropharyngeal and laryngeal surgery

Objectives

The objectives were to determine the surgical modality with the lowest aerosol and droplets generated by commonly used modalities in oropharyngeal and laryngeal surgery.

Methods

A simulation of oropharyngeal and laryngeal surgery was set up using fresh sheep heads. Four common surgical modalities were utilized: cold steel, electrocautery, coblation, and microdebrider. The resultant aerosol generated was evaluated using two measurement modalities at two key positions in the theater. (1) DustTrak Pro Aerosol Monitor was used to measure the concentration of particles. (2) Fluorescein dye coated on the oropharynx and larynx, and the resultant scatter on paper.

Results

Electrocautery and coblation produced statistically significant increases in the concentration of aerosols (p < .001). Microdebrider and cold steel instrumentation produced the least aerosols. No measurable fluorescein droplets were noted for all four modalities.

Conclusion

Electrocautery and coblation produced higher concentrations of aerosols. Mitigation factors should be considered with instruments with increased aerosolization. These modalities show low droplet-related infection risk.

Comparing Aerosol Generation in Human and Animal Tissues During Common Otolaryngology Procedures

OBJECTIVE

To determine whether hamster and human tissues generate similar amounts of aerosolized particles using common otolaryngology surgical techniques.

STUDY DESIGN

Quantitative experimental research.

STUDY SETTING

University research laboratory.

METHODS

Drilling, electrocautery, and coblation were performed on human and hamster tissues. Particle size and concentration were measured during the surgical procedures using a scanning mobility particle sizer and an aerosol particle sizer (SMPS-APS) and GRIMM aerosol particle spectrometer.

RESULTS

SMPS-APS and GRIMM measurements detected at least 2-fold increases in aerosol concentrations compared to baseline during all procedures. Procedures performed on human and hamster tissues produced similar trends and order of magnitude of aerosol concentrations. Generally, hamster tissues produced higher aerosol concentrations compared to human tissues, and some of these differences were statistically significant. Mean particle sizes for all procedures were small (<200 nm), although statistically significant differences in particle size were identified between human and hamster tissues during coblation and drilling.

CONCLUSION

Aerosol-generating procedures performed on human and hamster tissue produce similar trends in aerosol particle concentrations and sizes, although we observed some differences between the 2 tissue types. Further studies should be performed to understand the clinical significance of these differences.

Aerosol Generation During Nasal Airway Instrumentation

OBJECTIVE

Airborne aerosol transmission, an established mechanism of SARS-CoV-2 spread, has been successfully mitigated in the health care setting through the adoption of universal masking. Upper airway endoscopy, however, requires direct access to the face, thereby potentially exposing the clinic environment to infectious particles. This study quantifies aerosol production during rigid nasal endoscopy (RNE) and RNE with debridement (RNED) as compared with intubation, a posited gold standard aerosol-generating procedure.

STUDY DESIGN

Prospective cross-sectional study.

SETTING

Subspecialty single-center clinic and surgical study.

METHOD

Three aerosol detectors (NANOSCAN-3910, OPS-3330, and APS-3321) with a particle size sensitivity of 10 to 20,000 nm were utilized to detect particulate production during the clinical care of 209 patients undergoing RNE/RNED and 25 patients undergoing intubation.

RESULTS

RNE and RNED produced statistically significant particles over baseline in 29.3% and 51.0% of subjects (P = .003-.049 and .002-.047, respectively). Intubation produced statistically significant particles in 31.2% (P = .001-.015). The mean ± SD particle diameter in all tests was 69.9 ± 10.5 nm with 99.7% <300 nm. There were no statistical differences in particle production among RNE, RNED, and intubation. The presence of concomitant cough, sneeze, or prolonged speech similarly did not significantly affect particle production during any procedure.

CONCLUSIONS

Instrumentation of nasal airway produces airborne aerosols to a similar degree of those seen during intubation, independent of reactive patient behaviors such as cough or sneeze. These data suggest that an improved understanding is necessary of both the definition of an aerosol-generating procedure and the functional consequences of procedural aerosol generation in clinical settings.