The Science Journal of the American Association for Respiratory Care

2009 OPEN FORUM Abstracts

MODEL OF THE RESPIRATORY SYSTEM WITH GAS EXCHANGE SIMULATION

Jaroslav Marek, Karel Roubik; Faculty of Biomedical Engineering, Czech Technical University in Prague, Kladno, Czech Republic

Background: Models of the respiratory system are widely used in education, equipment testing and calibrations. They simulate mechanical parameters of the respiratory system but only a few of them can simulate gas exchange. The aim of the study is to design an educational mechanical model of the respiratory system of an adult human that is able to simulate gas exchange in the lungs and allows studying effects of ventilatory parameters changes upon the alveolar gas composition. Method: The main part of the model is represented by a ‘metabolic unit’ consisting of a propane-butane (PB) burner and a water cooler. Burning of PB assures oxygen consumption and CO2 production. The analogous respiratory quotient for PB is RQ=0.6. The metabolic unit is encased in a rigid plexiglass chamber. Its volume of 137 liters yields an adiabatic compliance of 1 L/kPa which corresponds to the compliance of an adult respiratory system. Airway resistance may be adjusted using exchangeable parabolic resistances and anatomic dead space may be modified by attaching an extra volume to the input port of the model. For educational purposes, a respiratory monitor is placed between the model and a ventilator for VT, f, MV, FIO2, Crs and Raw monitoring. Simulated alveolar gas is sampled from the chamber and alveolar FAO2 and FACO2 are analyzed. Results: The model is able to simulate mechanical parameters of an adult respiratory system. Crs measured by Veolar ventilator (Hamilton Medical, Rhäzüns, Switzerland) is 1.06 L/kPa. For physiological ventilatory parameters (VT=500 mL, f=18 bpm), the steady alveolar FAO2 is 0.16. Hypoventilation leads to the PB flame extinguishment. Conclusion: The model allows students to study influence of ventilatory parameters upon the alveolar gas composition, to understand RQ, importance and effect of anatomic dead space, etc. The model is used for education at the Faculty of Biomedical Engineering, CTU in Prague. Acknowledgment: Supported by grant MSM 6840770012. Sponsored Research - Supported by grant MSM 6840770012

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