title: Airflow dynamics of coughing in healthy human volunteers by shadowgraph imaging: an aid to aerosol infection control.
abstract: Cough airflow dynamics have been previously studied using a variety of experimental methods. In this study, real-time, non-invasive shadowgraph imaging was applied to obtain additional analyses of cough airflows produced by healthy volunteers. Twenty healthy volunteers (10 women, mean age 32.2±12.9 years; 10 men, mean age 25.3±2.5 years) were asked to cough freely, then into their sleeves (as per current US CDC recommendations) in this study to analyze cough airflow dynamics. For the 10 females (cases 1-10), their maximum detectable cough propagation distances ranged from 0.16-0.55 m, with maximum derived velocities of 2.2-5.0 m/s, and their maximum detectable 2-D projected areas ranged from 0.010-0.11 m(2), with maximum derived expansion rates of 0.15-0.55 m(2)/s. For the 10 males (cases 11-20), their maximum detectable cough propagation distances ranged from 0.31-0.64 m, with maximum derived velocities of 3.2-14 m/s, and their maximum detectable 2-D projected areas ranged from 0.04-0.14 m(2), with maximum derived expansion rates of 0.25-1.4 m(2)/s. These peak velocities were measured when the visibility of the exhaled airflows was optimal and compare favorably with those reported previously using other methods, and may be seen as a validation of these previous approaches in a more natural setting. However, the propagation distances can only represent a lower limit due to the inability of the shadowgraph method to visualize these cough airflows once their temperature cools to that of the ambient air, which is an important limitation of this methodology. The qualitative high-speed video footage of these volunteers coughing into their sleeves demonstrates that although this method rarely completely blocks the cough airflow, it decelerates, splits and redirects the airflow, eventually reducing its propagation. The effectiveness of this intervention depends on optimum positioning of the arm over the nose and mouth during coughing, though unsightly stains on sleeves may make it unacceptable to some.
authors.affiliation: Department of Laboratory Medicine, National University Hospital, Queenstown, Singapore. jwtang49@hotmail.com
authors.forename: Julian W
authors.initials: JW
authors.lastname: Tang
authors.forename: Andre
authors.initials: A
authors.lastname: Nicolle
authors.forename: Jovan
authors.initials: J
authors.lastname: Pantelic
authors.forename: Gerald C
authors.initials: GC
authors.lastname: Koh
authors.forename: Liang De
authors.initials: LD
authors.lastname: Wang
authors.forename: Muhammad
authors.initials: M
authors.lastname: Amin
authors.forename: Christian A
authors.initials: CA
authors.lastname: Klettner
authors.forename: David K W
authors.initials: DK
authors.lastname: Cheong
authors.forename: Chandra
authors.initials: C
authors.lastname: Sekhar
authors.forename: Kwok Wai
authors.initials: KW
authors.lastname: Tham
mesh_terms: D000328:Adult; D002487:Centers for Disease Control and Prevention, U.S.; D003140:Communicable Disease Control / Q000379:methods; D003371:Cough; D005260:Female; D005540:Forced Expiratory Flow Rates; D017408:Guidelines as Topic; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter; D014481:United States; D014741:Video Recording; D055815:Young Adult
chemical_list: D052638:Particulate Matter