Micromachined catheter flow sensor and its applications in breathing measurements in animal experiments

A combination of silicone oil and a parylene film coating was newly introduced in the packaging process of a catheter flow sensor for measuring breathing characteristics under high humidity conditions. The produced catheter flow sensor was used in two animal experiments described in this paper to verify its usefulness. At first, it was inserted into the air passage of a mouse, and then methacholine was given to it to provoke contraction of the air passage. The sensor could directly detect the breathing characteristics successfully. Then, the sensor was inserted into a rabbit bronchus by using a guide tube and a fiberscope. The position of the tube’s fore-end was confirmed from images taken using the fiberscope. The sensor directly evaluated the breathing characteristics of rabbits with and without a pneumothorax. We conclude from these results that our developed catheter flow sensor can be used in the future to directly measure the breathing characteristics in a bronchus.