Exhaled Air Dispersion during Coughing with and without Wearing a Surgical or N95 Mask

Abstract

ObjectivesWe compared the expelled air dispersion distances during coughing from a human patient simulator (HPS) lying at 45° with and without wearing a surgical mask or N95 mask in a negative pressure isolation room.MethodsAirflow was marked with intrapulmonary smoke. Coughing bouts were generated by short bursts of oxygen flow at 650, 320, and 220L/min to simulate normal, mild and poor coughing efforts, respectively. The coughing jet was revealed by laser light-sheet and images were captured by high definition video. Smoke concentration in the plume was estimated from the light scattered by smoke particles. Significant exposure was arbitrarily defined where there was ≥ 20% of normalized smoke concentration.ResultsDuring normal cough, expelled air dispersion distances were 68, 30 and 15 cm along the median sagittal plane when the HPS wore no mask, a surgical mask and a N95 mask, respectively. In moderate lung injury, the corresponding air dispersion distances for mild coughing efforts were reduced to 55, 27 and 14 cm, respectively, p < 0.001. The distances were reduced to 30, 24 and 12 cm, respectively during poor coughing effort as in severe lung injury. Lateral dispersion distances during normal cough were 0, 28 and 15 cm when the HPS wore no mask, a surgical mask and a N95 mask, respectively.ConclusionsNormal cough produced a turbulent jet about 0.7 m towards the end of the bed from the recumbent subject. N95 mask was more effective than surgical mask in preventing expelled air leakage during coughing but there was still significant sideway leakage.

A Cough Aerosol Simulator for the Study of Disease Transmission by Human Cough-Generated Aerosols

“…Pantelic et al (2009) used a coughing aerosol simulator to test a personalized ventilation system and found that the system offered partial protection, but that cough aerosols were still able to penetrate through it. Hui et al (2012) studied the dispersion of small aerosol particles from a human patient simulator during coughing and found that forward dispersion was reduced and lateral dispersion increased by the use of surgical masks and N95 respirators.…”

Exhaled air dispersion during bag-mask ventilation and sputum suctioning - Implications for infection control

“…Moreover, water content in the respiratory droplets may be evaporated and hence produce small droplet nuclei that are suspended in air. Nevertheless, the smoke particles used in this study mark the continuous air phase, and therefore our data indicated the anticipated "upper limits" of droplet dispersion [10][11][12][13][14][15][16]21 .…”

“…We inserted a size 10 FG suction catheter into the oral cavity. In order to simulate normal, mild and poor coughs, we generated short bursts (20 ms) of airflow through the catheter at 650, 320, and 220 L/min, respectively 21 . The trachea was then intubated with a 9 mm tracheal tube ( Fig.…”

“…Smoke particles of <1 μm in diameter, produced by a M-6000 smoke generator (N19, DS Electronics, Sydney, Australia) was used to highlight exhaled airflow as previously described [10][11][12][13][14][15][16]21,24 . A 6 FG catheter was inserted into the right main bronchus of the HPS to deliver smoke particles.…”

“…After mixing with alveolar gas, smoke particles were exhaled through the normal airway passage. Leakage jet plume were then illuminated by a green (532 nm wavelength) laser light-sheet using a continuous pulse, diode-pumped solid state laser generator (OEM UGH-800 mW, Lambdapro Technologies, China) [10][11][12][13][14][15][16]21 . Assuming the intensity of the laser and the size or shape of the smoke particles remained constant during examination 24 , the intensity of light scattered by the smoke particles indicated the exhaled air smoke concentration.…”