Performance Improvement and Evaluation for Indirect Calorimetry in Small Preterm Infants

• Main Authors: Shih-ching Lin, 林詩清
• Other Authors: Ching-Hsing Luo
• Format: Others
• Language: en_US
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/54777289489693391551

博士 === 國立成功大學 === 電機工程學系 === 89 === An indirect calorimetry system of measuring oxygen consumption and carbon dioxide production has been frequently used for preterm infants. The energy consumption and metabolic measurements are based on flow-through technology. The noninvasive measurement feature of the indirect calorimeter is widely used in pediatric clinical research. However, the indirect calorimeter has several limitations for small preterm infants, particularly the ill infant weighing < 1.0 kg. In this study, we propose some technologies and methodologies to improve the performance of the indirect calorimetry. According to these technologies and methodologies, we redesign the indirect calorimeter proposed in our pervious study. For supplying stable inspiratory gas, a fuzzy PID oxygen control system is designed to adjust oxygen concentration. The oxygen controller that designed for premature infants is based on fuzzy control logic to automatically adjust the mixing ratio of room air and pure oxygen gas from the hospital''s supply system. It is designed to reduce the risks of oxygenic toxicity and retinopathy of prematurity by lowering the overshoot of oxygen concentration. Its performance was evaluated and optimal membership functions were obtained. The system is quite robust with little effect by disturbance and has little or no overshoot when step changing the level of oxygen concentration in the mixed gas. A new apparatus of alcohol-burner is designed for calibration and evaluation. It is based on alcohol combustion to mimic infant''s breath. The evaluation at the different alcohol combustion rates and several air-extracting flow rates is used to survey the improved performance. As the results, the accuracy and precision are enhanced by these methods and the lowest oxygen consumption rate, 3.9 ml/min, fits for baby weight of 0.66 kg. It is demonstrated that the performances of new indirect calorimetry are substantially improved. It can be applied to calculate the energy consumption and metabolic rate for low-birth-weight infants in clinical research. 1.1 Stable inspiratory gas concentration 1.2 Collect completely mixed expiratory gas 1.3 Reduce measurement error in small gas volume 1.4 Frequent calibration in measurement process Chapter 2 INSTRUMENT DESIGN 2.1 Inspiratory Gases Supply System 2.1.1 Simulating Fuzzy PID Oxygen Controller 2.1.2 Implementing Fuzzy PID Oxygen Controller 2.2 Measurement of VO2 and VCO2 2.2.1 Calculation of VO2 and VCO2 from open-circuit apparatus 2.3 Hood Design 2.4 Sampling and Controlling Circuit 2.5 The Processes of Measurement and Controlling in Software Design 2.6 Calibration and Laboratory Evaluation 2.6.1 Standard gas calibration 2.6.2 Metabolic measurement simulations 2.6.3 Respiration simulations 2.6.4 Design of the automatic alcohol burner Chapter 3 RESULTS 3.1 Fuzzy PID Oxygen Controller 3.2 Calorimeter Laboratory Evaluation Chapter 4 DISCUSSION Chapter 5 CONCLUSIONS REFERENCES Appendix A Photographs of Indirect Calorimetry and Alcohol-burner System Appendix B Calculation of Energy Production from VO2 & VCO2 Appendix C Gas analyzers C.1 CO2 Analyzer--Uras 14 Infrared Analyzer Module C.1.1 Analyzer module structure C.1.2 Measurement principle C.1.3 Calibration C.2 O2 Analyzer--Magnos 16 Oxygen Analyzer Module C.2.1 Analyzer module structure C.2.2 Measurement principle characteristics Appendix D The Principle of Mass Flow Meter Appendix E Schematics of the sampling and controlling circuit and alcohol burner VITA