# HW6_solutions - BIOE 398BS Quantitative Human Systems...

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BIOE 398BS: Quantitative Human Systems Physiology Spring 2008 Bioengineering, University of Illinois at Urbana-Champaign 1 Problem Set 6. Due Friday, February 29, 2008 at the beginning of class. 1. What factors determine: a. Total Lung Capacity? Total lung capacity refers to the total volume of air in the lung. It is the sum of vital capacity and residual lung volume. The total lung capacity is reached when the chest is maximally expanded, hence the force outward on the chest wall due to the external intercostals (and downward due to the diaphragm) is exactly balanced by the force inward due to the elastic recoil pressure of the lungs and the chest. All lung volumes are a balance between outward forces from the chest wall and its muscles and inward forces of the elastic recoil of the lungs. The coupling of these two is maintained by the fluid filled pleural space. b. Residual Volume? The residual volume is the volume of air remaining in the lungs after maximal expiration. The residual volume is the point at which the internal intercostal muscles are no longer able to reduce the volume of the thoracic cavity. 2. What is the volume of the anatomical dead space in respiration? What percentage of a total breath does this represent? Where does this “dead volume” air reside in the respiratory space at the end of expiration? Where does it reside at the end of inspiration? Assume that the breathing time, ie time for inspiration and expiration, is very short. The anatomical dead space is the volume of space in the respiratory system that does not participate in gas exchange. It is the volume of air that remains in the conducting pathways at the end of expiration, ie. volume that is trapped in the pathways and not exchanging with outside air. It is approximately 150 mL, corresponding to about 30% of a normal breath. At the end of expiration it is in the conducting pathways of the

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HW6_solutions - BIOE 398BS Quantitative Human Systems...

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