| This Ph.D. dissertation describes the development of an indirect calorimetry system for use in a critical care setting. Indirect calorimetry systems measure the rate of oxygen consumed ( V&d2;O2 ) by a patient, the rate of carbon dioxide produced ( V&d2;CO2 ), and the respiratory quotient (RQ) or the ratio of V&d2;CO2 to V&d2;O2 . The clinical determination of V&d2;O2, V&d2;CO2 and RQ values from patients undergoing mechanical ventilation therapy is useful in the determination of patient metabolic energy expenditure as well as the proportionate determination of substrate (protein, fat and carbohydrate) utilization. This information is valuable from a clinical standpoint for determination of proper nutritional management of critically ill (ventilator dependent) patients. Caloric mismanagement has been associated with increased morbidity and mortality as well as increased hospital stay. Further, improper management of substrate balance may produce ventilator weaning difficulties. A compact indirect calorimetry system capable of obtaining and tracking these measurements in real time using an on airway sensor would represent a significant advancement in the state of the art of medical care. This advancement would allow physicians to tailor nutritional support to the current needs of patients as well as making possible the tracking of nutritional parameters, while not necessitating the temporary removal of patients from life support systems. The system developed herein solves algorithm challenges that such a system would present. The ultimate goal of this dissertation is to set the foundation for an improvement in critical care medicine delivery. |
