Physical Methods Simulating Mechanisms of the Human Cough: Elimination of Radiopaque Material From the Bronchi of Dogs

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Abstract
A 24% aqueous suspension of Thorotrast thickened with mucin was employed as the contrast medium and instilled by bronchoscope into the right lower lobe of treated and control animals. In 15 of 19 dogs exposed for 2 hrs. to high expiratory flow rates produced in the exsufflator X-rays of the bronchi revealed definite decrease in the amt of contrast medium retained, i.e., approx. 70% of the material introduced. The forces involved in this procedure include a high expiratory flow rate of air approx. 65% of that of a vigorous cough; a 2-fold dilation of the medium-sized bronchi; and abrupt narrowing and shortening of the bronchial tree during the high velocity expiration. The relaxation pressure of the lungs and surrounding structures is responsible for the high expiratory flow rates and the abrupt decrease in bronchial diameters. In 24 dogs treated for 1 and 2 hrs. in the mechanical cough chamber, over 90% of the instilled contrast medium was eliminated in all instances. In an equal number of control animals negligible changes in the bronchogram were observed. The physical forces operating in this procedure simulate more nearly those employed in an effective human cough; these include prevention of expansion of the lungs, compression of the chest and abdomen, pressures that tend to elevate the diaphragm, and a rapid outflow of air from the lungs.
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