Micro-machined respiratory monitoring system development for artificial ventilator in animal experiment

We developed a respiratory monitoring system to evaluate elasticity on the lungs of small animals by the positive-pressure airflow under artificial ventilation during experiments. The system consists of a tube-type thermal flow sensor fabricated using microelectromechanical systems (MEMS) technology and commercially available Si-MEMS pressure sensors. We first used a small spherical balloon having an inner volume of 0.68 cc as a simulated lung. We evaluated the balloon elasticity from the supplied flow volume and pressure inside the balloon and confirmed that our system can detect balloon elasticity from the gradient under both static and cyclic airflow. We evaluated our system in terms of the lung elasticity of a rat and obtained a flow volume vs. pressure curve showing the lung elasticity under artificial ventilation. The changes in the flow rate and pressure waveforms due to airway contraction with drug administration were detected with our system in real time.