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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An Analysis of Respiratory Mechanisms Controlling Exercise Hyperpnea During Cycle Ergometry Conducted at Selected Workloads and Pedal Frequencies

Wise, Charles Hamilton 12 1900 (has links)
Respiratory and metabolic patterns in response to variations in exercise workload (WL) and pedal frequency (RPM) were examined in 10 healthy males. Each subject performed WLs of low (L), moderate (M) and high (H) intensity, equivalent to 25%, 50% and 75% V02 m a x at 7 pedal frequencies (40, 50, 60, 70, 80, 90 and 100 RPM). ANOVA ( 3 X 7 design) indicated that WL and RPM had independent and significant effects on all respiratory and metabolic measures; i.e., the greater the WL and RPM, the higher the HR, V02, VC02, Ve, Fb, Vt, Vt/Ti, Vt/Te and Ti/TtQt and the lower the Ti and Te. However, analysis of the interaction effect revealed different response patterns for Fb, Vt, Ti, Vt/Ti, Vt/Te and Ve among the WLs. During L-WL, increases in RPM produced increases in Ve which were due to progressive increases in both Fb and Vt. However, during M-WL and H-WL, increases in RPM produced increases in Ve which were accomplished by a constant Vt and a progressive increase in Fb. My findings suggest that during low WLs, the signal for Vt is dependent on rate of contraction, while during M-WL and H-WL, the signal for Vt appears to depend on force of contraction and is independent of increasing RPM. When comparing the L-WL and M-WL, alterations in Ve, Fb, Vt/Ti and Vt/Te in relation to increases in pedal frequency were additive. However, when these two lower WLs were compared to the H-WL, the interaction between pedal frequency and Ve, Fb, Vt/Ti and Vt/Te was multiplicative. In addition, the interaction between WL and RPM on Vt and Ti was additive when comparing the M-WL and H-WL and multiplicative when these two lower WLs were compared to the H-WL. Correlation analysis indicated that for all WLs, Te was more highly related to Fb than was Ti, while Vt/Te was more highly related to Ve than was Vt/Ti. Our findings suggest that during M-WL and H-WL, increases in Ve are accomplished by progressive increases in Fb and decreases in Te, while during L-WL, increases in Ve are achieved by progressive increases in both Fb and Vt.
2

Modeling and control of a pressure-limited respirator and lung mechanics

Li, Hancao 05 April 2013 (has links)
The lungs are particularly vulnerable to acute, critical illness. Respiratory failure can result not only from primary lung pathology, such as pneumonia, but also as a secondary consequence of heart failure or inflammatory illness, such as sepsis or trauma. When this occurs, it is essential to support patients with mechanical ventilation while the fundamental disease process is addressed. The goal of mechanical ventilation is to ensure adequate ventilation, which involves a magnitude of gas exchange that leads to the desired blood level of carbon dioxide, and adequate oxygenation that ensures organ function. Achieving these goals is complicated by the fact that mechanical ventilation can actually cause acute lung injury, either by inflating the lungs to excessive volumes or by using excessive pressures to inflate the lungs. Thus, the challenge to mechanical ventilation is to produce the desired blood levels of carbon dioxide and oxygen without causing further acute lung injury. In this research, we develop an analysis and control synthesis framework for a pressure-limited respirator and lung mechanics system using compartment models. Specifically, a general mathematical model is developed for the dynamic behavior of a multicompartment respiratory system. Then, based on this multicompartment model, an optimal respiratory pattern is characterized using classical calculus of variations minimization techniques for inspiratory and expiratory breathing cycles. Furthermore, model predictive controller frameworks are designed to track the given optimal respiratory air flow pattern while satisfying control input amplitude and rate constrains.

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