Quantification and visualization of aerosols in ear, nose, and throat exam and flexible laryngoscopy

Abstract

Objective: To measure and visualize aerosol generation during ear, nose, and throat (ENT) exam and flexible laryngoscopy, as safety recommendations are currently to defer routine and low-priority examinations.

Methods: Aerosols generated during ENT examination and flexible laryngoscopy were quantified by laser aerosol spectrometry and visualized live by high-speed imaging during those procedures for three participants who were tested three times for each test.

Results: Routine ENT examination and flexible laryngoscopy produce aerosols at levels comparable to normal breathing and speech.

Conclusion: During ENT examination and flexible laryngoscopy, the practitioner should wear a surgical mask and potentially contaminated surfaces should be cleaned after the procedure. For flexible laryngoscopy, it is recommended in addition that the patient wear a mask over the mouth in case the procedure induces a sneeze. The time during which the patient is unmasked should be minimized. In these settings, the risk to the practitioner is minimal unless the patient is sneezing or symptomatic.

Level of evidence: 1.

Keywords: COVID‐19; ENT examination; aerosols; flexible laryngoscopy; safety.

FIGURE 1

Experimental setup. The experimental setup for laser aerosol spectrometry viewed from the right (A) with the laser aerosol spectrometer (LAS) aspiration tube (red arrow) fixed 10 cm in front of the participant. The experimental setup for laser aerosol spectrometry viewed from the front left side with the circular doors (red arrow) opened for the practitioner to perform a flexible laryngoscopy without interfering with aerosol measurements (B). The experimental setup for live aerosol imaging showing the positioning of the camera, green laser sheet and participant (C).

FIGURE 2

Aerosol and droplets quantification using aerosol spectrometry during normal breathing, normal speech, routine clinical examination procedures, and flexible laryngoscopy. Normal breathing and normal speech were assessed both with a surgical mask and with no mask, while other procedures were assessed only with no mask as they are impossible to perform with the participant wearing a mask. Procedures were performed in the SplashGuard Plexiglass box. Particles were counted using a LAS and normalized to log₁₀ particles per SLPM. Three different participants were tested for every procedure, three times each (total n = 9). No particles were detected for all repetitions of normal breathing and speech with surgical mask (plotted at log₁₀ particles per SLPM = 0). No statistical difference was observed between the six tests with no mask.

FIGURE 3

Aerosol and droplets quantification using aerosol spectrometry for coughing and sneezing. Evaluations were performed during normal breathing with a surgical mask, normal speech with a surgical mask, normal breathing without mask, coughing without mask, and sneezing simulations without mask or with two‐layer cloth mask and surgical masks. Procedures were performed in the SplashGuard Plexiglass box. Particles were counted using a laser aerosol spectrometer (LAS) and normalized to log₁₀ particles per standard litre per minute (SLPM). Three different participants were tested for every procedure, three times each (total n = 9). No particles were detected for all repetitions of normal breathing and speech with surgical mask and for three repetitions of sneezing with surgical mask (plotted at log₁₀ particles per SLPM = 0). Statistical comparison to normal breathing is shown for every test.

FIGURE 4

Laser aerosol imaging representative images. Aerosol and droplets visualization during flexible laryngoscopy removal with the participant with no mask (A) and wearing a surgical mask (B) during the procedure. Aerosol and droplets visualization during sneezing with the participant with no mask (C) and wearing a surgical mask (D). Aerosol and droplets visualization during coughing with the participant with no mask (E) and wearing a surgical mask (F). Complete videos are available in online‐only material.