Implementering av Patientsimulator för Anestesimaskiner
In order to facilitate testing of anesthesia machines a patient simulator has been required by Maquet Critical Care AB. A patient simulator has been developed to reduce expensive and time consuming animal experiments and temporary lab arrangements. The patient simulator has been developed and designed to simulate human lungs with regards to anesthetic uptake, production of carbon dioxide and heating and moisturizing exhaled air.The system comprises a container and a test lung to simulate the volume and the dynamic of the human lung. The simulation of uptake of anesthetics has been implemented by pumping a fraction of the gas from the container through a bypass circuit with an active charcoal filter that adsorbs volatile anesthetics. The flow through the bypass circuit is generated by a pump and is controlled by a linear valve.The resulting performance of the patient simulator has fulfilled the requirements. A verification of the performance has been done by weighing the anesthetic uptake filter and comparing it with calculated values. The exhaled simulator imitates human lungs to a large extent.The simulation of uptake of anesthetics follows a model that is a modification of a well known model. A modification of the model was made in order to handle changes in agent concentration.The carbon dioxide production was implemented by dosing carbon dioxide from a gas tank through a mass flow controller. The carbon dioxide in the system can be set to a constant flow to achieve a certain production rate or set to achieve a desired concentration in the exhaled gas.To achieve moisture and right temperature in the exhaled air, a humidification chamber with water with heating elements was used. A connection to the humidification chamber with non return valves was used to guide the exhalation gas through the humidification chamber while bypassing the inhalation gas. This minimizes the humidity uptake in the charcoal filter.To monitor and control the system, a program was made in LabVIEW. The graphical user interface of this program consists of a control panel where measurement data of the system is displayed. Settings of patient data and other parameters are also made here. The program handles the communication with the process using a data acquisition and instrument control device.A PI-controller with gain scheduling and anti-windup was implemented to control the flow through the anesthetic uptake filter. The parameters of the controller were tuned experimentally.