Influence of airway structure on gas expirograms
Bioengineering research has been conducted in the area of respiratory gas transport to determine the effects of emphysema, a chronic obstructive pulmonary disease (COPD), on the shape of the CO$\sb2$ expirogram and to develop a reliable noninvasive pulmonary function test sensitive to this disorder that afflicts 14 million Americans and is attributable to over 100,000 deaths annually. This work has also contributed to the basic science of pulmonary physiology in healthy lungs, since details of the interactions of gas transport, pulmonary circulation, and airway anatomy are not completely understood. A single-path theory of respiratory gas transport has been developed into a computer model that simulates the movement of gases from the alveolar-blood interface to the mouth during tidal air flow in a single-path model (SPM) of the entire bronchial tree, with a small number of adjustable input parameters representing physical, physiological, and anatomical features of real lungs. SPM simulations were compared to steady state gas expirograms measured on healthy subjects and patients with COPD. Instrumentation consisted of hardware and software developed for a computerized fast-response quadrapole mass spectrometer system that is capable of simultaneously measuring CO$\sb2$ and infused inert gas expirograms. After extensive experimental and simulation studies on data from healthy subjects and patients with COPD, an optimization algorithm was developed to find the structural SPM input parameters necessary to fit simulated gas washout results to experimental data from any particular subject. Through the interaction of laboratory experiments and numerical modeling, the basis for a pulmonary function test has evolved that quantifies the gas transport limitation and the alveolar tissue obliteration of emphysema, and is corroborated by conventional pulmonary function test data. This is the first time that acinar airway information has been recovered from gas expirograms that is seen to distinguish between health and disease. ^
Jeffrey D Schwardt,
"Influence of airway structure on gas expirograms"
(January 1, 1992).
Dissertations available from ProQuest.