Effectiveness of cough etiquette maneuvers in disrupting the chain of transmission of infectious respiratory diseases

Abstract

Background: The effectiveness of recommended measures, such as "cover your mouth when coughing", in disrupting the chain of transmission of infectious respiratory diseases (IRD) has been questioned. The objective of the current study was to determine the effectiveness of simple primary respiratory hygiene/cough etiquette maneuvers in blocking droplets expelled as aerosol during coughing.

Method: In this study, 31 healthy non-smokers performed cough etiquette maneuvers in an effort to cover their voluntarily elicited best effort coughs in an open bench format. A laser diffraction system was used to obtain accurate, non-invasive, quantitative, real time measurements of the size and number of droplets emitted during the assessed cough etiquette maneuvers.

Results: Recommended cough etiquette maneuvers did not block the release and dispersion of a variety of different diameter droplets to the surrounding environment. Droplets smaller than one-micron size dominate the total number of droplets leaked when practicing assessed maneuvers.

Conclusions: All the assessed cough etiquette maneuvers, performed as recommended, do not block droplets expelled as aerosol when coughing. This aerosol can penetrate profound levels of the respiratory system. Practicing these assessed primary respiratory hygiene/cough etiquette maneuvers would still permit direct, indirect, and/or airborne transmission and spread of IRD, such as influenza and Tuberculosis. All the assessed cough etiquette maneuvers, as recommended, do not fully interrupt the chain of transmission of IRD. This knowledge urges us all to critically review recommended CE and to search for new evidence-based procedures that effectively disrupt the transmission of respiratory pathogens. Interrupting the chain of transmission of IRD will optimize the protection of first responders, paramedics, nurses, and doctors working in triage sites, emergency rooms, intensive care units, and the general public against cough-droplet-spread diseases.

Figure 1

Laser and sensor arrangement for assessment of surgical mask and hand as barriers.

Figure 2

Laser and sensor arrangement for assessment of using the arm/sleeve as a barrier.

Figure 3

Laser and sensor arrangement for assessment of using a tissue as a barrier.

Figure 4

Average droplets detected per cough etiquette maneuver. Control: Size and number of droplets expelled by healthy non-smokers when coughing. Data acquired from an expanding unobstructed cough aerosol. CE data: The short distance from the mouth to the barrier prevents the expansion of the cough plume, and the shape of the barrier redirects a more concentrated flow across the measurement zone. The non-expanding concentrated plume would bring droplets travelling in the periphery closer to the center of the plume increasing the number of droplets accounted for. Particles deposited within the fiber network of tissues and surgical masks during the manufacturing process might be dislodged when coughing, hence increasing the number of items detected by the system.