An Accurate Metabolic Simulator for Indirect Calorimetry System Validation

University of Utah

A metabolic simulator capable of simulation of respiratory oxygen consumption (VO₂) and carbon dioxide production (VCO₂) for validation of indirect calorimetry systems is described. The metabolic simulator adds/removes respiratory gases by way of mass flow controllers to/from a physiologically realistic lung simulator (Michigan Instruments Inc. Training/Test Lung). The metabolic simulator and Michigan Instruments Training/Test Lung in combination are capable of simulating a wide range of metabolic and physiologic lung conditions. Simulation of VCO₂ is achieved by adding controlled amounts of carbon dioxide to the Training/Test Lung every (mechanical ventilator delivered) breath cycle. VO₂ simulation consists of adding controlled amounts of nitrogen and removing controlled amounts of inspiratory gas from the Training/Test Lung every breath. Real time monitoring of ventilation parameters is obtained from a Novametrix Cosmo+ respiratory profile monitor and control of gas flow through the simulator is achieved by way of a programmed IBM personal computer.