Determinants of respiratory tract aerosol generation in a diverse clinical population: an observational study

Rationale:
Respiratory tract infections are transmitted in part by infectious aerosol. Developing a greater understanding of how clinical and demographic factors affect aerosol generation could help to identify airborne infection ‘superspreaders’.

Objectives:
To measure respiratory aerosol from a diverse clinical population, exploring the impact of demographics, physiological factors and disease status.

Methods:
We recruited people with chronic lung disease, respiratory infection and healthy volunteers. We sampled aerosol from an enclosed circuit to exclude background non-respiratory aerosol, uniquely enabling bedside measurements of respiratory aerosol generation from an unwell population, while participants performed simple manoeuvres such as speaking and coughing.

Measurements and main results:
Across 128 participants, we detected lower aerosol generation among patients with a lung disease during a forced expiratory manoeuvre. This is likely to be related to differences in forced exhalation rather than demographic or clinical status. We observed a 500-fold variation in peak aerosol production when coughing. There was an association between aerosol generation and higher body mass index during coughing, but not with other clinical or demographic factors, and most of the variation remained unexplained.

Conclusions:
Our measurement of respiratory aerosol generation from patients with lung disease and infection is comparable with those published previously for healthy subjects. The amount of aerosol generation across the studied population was most closely linked with expiratory flow. While we observed variation in respiratory aerosol generation between participants in a clinical environment, there was no meaningful impact of demographics or respiratory disease on aerosol generation.