scholarly journals Tracer Gas Exposure of Human Subjects Doing Simulated Work at a Benchtop Enclosing Hood in a Wind Tunnel

2013 ◽  
Author(s):  
Rolando A. Carreno-Chavez
Keyword(s):  
Wind Tunnel ◽  
Human Subjects ◽  
Tracer Gas ◽  
Gas Exposure

scholarly journals A schlieren optical study of the human cough with and without wearing masks for aerosol infection control

2009 ◽  
Vol 6 (suppl_6) ◽  
Author(s):  
Julian W. Tang ◽  
Thomas J. Liebner ◽  
Brent A. Craven ◽  
Gary S. Settles
Keyword(s):  
High Speed ◽  
Fluid Dynamic ◽  
Human Subjects ◽  
Tracer Gas ◽  
Airborne Infection ◽  
Dynamic Mechanisms ◽  
Human Volunteers ◽  
Natural Mechanism ◽  
Time Changes ◽  
Aerosol Infection

Various infectious agents are known to be transmitted naturally via respiratory aerosols produced by infected patients. Such aerosols may be produced during normal activities by breathing, talking, coughing and sneezing. The schlieren optical method, previously applied mostly in engineering and physics, can be effectively used here to visualize airflows around human subjects in such indoor situations, non-intrusively and without the need for either tracer gas or airborne particles. It accomplishes this by rendering visible the optical phase gradients owing to real-time changes in air temperature. In this study, schlieren video records are obtained of human volunteers coughing with and without wearing standard surgical and N95 masks. The object is to characterize the exhaled airflows and evaluate the effect of these commonly used masks on the fluid-dynamic mechanisms that spread infection by coughing. Further, a high-speed schlieren video of a single cough is analysed by a computerized method of tracking individual turbulent eddies, demonstrating the non-intrusive velocimetry of the expelled airflow. Results show that human coughing projects a rapid turbulent jet into the surrounding air, but that wearing a surgical or N95 mask thwarts this natural mechanism of transmitting airborne infection, either by blocking the formation of the jet (N95 mask), or by redirecting it in a less harmful direction (surgical mask).

Evaluation of alveolar amplitude response technique for determination of lung perfusion in exercise

1981 ◽  
Vol 50 (5) ◽  
pp. 1071-1078 ◽  
Author(s):  
S. C. Luijendijk ◽  
A. Zwart ◽  
A. M. van der Kooij ◽  
W. R. de Vries
Keyword(s):  
Venous Return ◽  
Human Subjects ◽  
Compartment Model ◽  
Quantitative Agreement ◽  
Experimental Results ◽  
Tracer Gas ◽  
Amplitude Response ◽  
Good Quantitative Agreement ◽  
Anesthetized Dogs

We investigated the influence of tracer gas venous return on the determination of pulmonary perfusion (Qp) using the alveolar amplitude response technique (AART) to evaluate the applicability of this technique at rest and during exercise. The venous return influence was calculated by a computer simulation applied to a simplified body compartment model. Using the AART method, which neglects the influence of venous return, a simulation based on acetylene as a tracer gas predicted an overestimation of the actual value of Qp ranging from 0 to 10% for all work loads investigated. These theoretical results were compared with experimental results. Experiments with human subjects with acetylene as the tracer gas yielded an underestimation of Qp of about 20% at rest and an overestimation of about 7% under different exercise conditions. Experiments with anesthetized dogs showed an underestimation of Qp of about 12% for acetylene and about 6% for halothane. The theoretical and experimental results related to exercise conditions are thus in good quantitative agreement. The experimental data obtained for acetylene with human subjects at rest and with anesthetized dogs are also in good quantitative agreement. However, they deviate considerably from theoretical predictions. This discrepancy may be due to the simplified body compartment model used in the calculations, which can considerably influence the calculated results, especially for conditions at rest. The main conclusion of this paper is that recirculating tracer gas does not unduly influence results for Qp obtained with the AART method when halothane is used as the tracer gas.

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