Analysis of aerosol production and aerosol dispersion during otologic surgery

As a respiratory disease, the transmission of Coronavirus disease (COVID-19) is mainly caused by small droplets and aerosols. Healthcare personnel are particularly exposed during otologic surgery given the continuity with the nasopharynx, where the viral load is high, and the use of high-speed instruments. The purpose of the present study is to test a model of droplet dispersion produced in the performance of a drilling procedure on human bone to provide information about its distribution and size of the deposit in similar conditions to those of an operating theatre, to design different preventive measures.

A mastoidectomy and trans-labyrinthine approach were performed on an embalmed human corpse using for irrigation during drilling methylene blue dye in physiological saline solution (pss) at a concentration of 0.324 mg/mL. The distribution of the drops was stablished using semi-absorbent papers of size 52 cm × 42 cm covering the area around the dissection field to a radius of 150 cm and on the corpse at different heights to check vertical dispersion. The collected deposit material was analysed with the microscope at different magnification objectives.

Droplets between 2 μm and 2.6 cm were obtained. The visualization of the coloured droplets in the horizontal plane at a magnification of 1.5 was detected at 150 cm from the focus of emission of milling particles.

According to our study, bone drilling with high speed motors under continuous saline irrigation in a haemorrhagic surgical field increases the amount of aerosols exposing healthcare personnel to additional airbone particles. This risk does not end in the operating rooms as particles smaller than 2 μm can be suspended in the air for hours and could exit the operating theatre due to the use of positive pressure systems. Thus, the use of N95, FFP2, FFP3 or PAPRS should be considered and the development of hood systems to prevent the dispersion of aerosols during these procedures should be considered.