Respiratory Particle Emission During Voice Assessment and Therapy Tasks in a Single Subject

SARS-CoV-2 is transmitted via respiratory particles. Respiratory particle emission is impacted by manner of breathing and voicing, as well as intersubject variability. Assessment and treatment of voice disorders may include tasks that increase respiratory particle emission beyond typical breathing and speaking. This could increase the risk of disease transmission via respiratory particles.

Respiratory particle emission was measured during a single-subject, repeated measures clinical simulation of acoustic and aerodynamic assessment and voice therapy tasks. An optical particle sizer was used to measure particle count (1-10 μm in diameter). Assessment and therapy tasks were completed in three conditions: (1) 15 cm from the device, (2) 1 m from the device, and (3) 1 m from the device with the subject wearing a surgical mask.

Condition 1 generated the highest particle count, with a median of 5.1 (13) additional particles above baseline, which was statistically significant (U = 381.5, P= 0.002). In condition 1, therapy and acoustic tasks combined produced more particles compared to the baseline and speech tasks, with a median difference of 6.5 additional particles per time point (U = 309.0, P= 0.002). This difference was not significant for conditions 2 and 3. Peak particle generation occurred in specific phonatory tasks, which was most pronounced in condition 1. Voice therapy tasks during condition 1 generated the highest peaks of normalized total particles with classical singing and expiratory muscle strength training. There was a significant difference in the amount of particle generation between condition 1 and 2, with a median difference of 5.2 particles (U = 461.0, P= 0.002). The particle count difference between conditions 2 and 3 was 2.1 (U = 282.0, P= 0.292), and this difference was not significant. The normalized total particles were assessed over time for each condition. For all conditions, there was no significant accumulation of particles.

For a single subject, production of voice assessment and therapy tasks combined resulted in an increased number of respiratory particles compared to speech and baseline (1-10 μm). EMST and classical singing generated the greatest concentration of particles. Respiratory particle counts were higher at 15 cm from the particle sizer compared to 1 m from the particle sizer, suggesting that physical distancing may reduce immediate clinician exposure to respiratory particles. Particle concentration did not accumulate over time.