Class: BE-310
Group: T5
Members: Seungtaek Lee, Chris Lindsey, Melinda Patterson, Edwin Tan
Date: May 4, 1998
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Abstract:
Coughing is the body’s initial defense when an increased amount of mucus or phlegm collects in the trachea or the larger bronchial tubes. The mucus is cleared when internal pressure, built up by raising the diaphragm and closing the glotis, is suddenly released and forced through the larger tubes of the lungs. Asthmatics often find it difficult to cough, due the constriction of the upper airways caused by subepithelial tissue thickening as well as smooth muscle contraction. Goldie and Pederson have determined that the "airway resistance is inversely proportional to the fourth power of tube radius" (Goldie p. 392). They are also plagued by increased viscosity of mucus, caused by plasma proteins that are associated with the condition. Through our experimentation, we modeled the upper airway with a pressurized tank (lung analog), a length of tube (trachea analog) a viscous fluid (mucus analog), and a solenoid valve (glotis analog). By varying the pressure in the tank, the diameter of the tube, and the viscosity of the fluid we were able to simulate the major characteristics of asthma. In our experiment, we found that for a 2/3 filled small tube, a pressure of 7 psi was sufficient to cough out the same amount as 10 psi in a 2/3 filled large tube at lower viscosity. In addition, we found that a complete clogging allowed a larger fraction of mucus to be coughed out within the whole range of viscosity tested. Even though the partially filled tube data and completely filled tube data differ, they show a consistent trend involving the viscosity of the solution. With increasing viscosity the fraction coughed out decreases. Therefore, it seems that the inability to create enough pressure coupled with increased resistance, due to a smaller airway, and increased mucus viscosity are the most dominant aspects of an asthmatic’s cough.