Measurement of heartbeat signals from airflow at mouth in rat by catheter flow sensor

We previously proposed heartbeat measurement by airflow at the mouth, and applied the catheter flow sensor to evaluate the airflow [1-3]. This time, we applied the drug to a rat to change the heartbeat frequency and tried to detect its change by catheter flow sensor. MEMS technology was used to fabricate the catheter flow sensor with an outer diameter of 1.8 mm to be applied to the measurement in the rat. The catheter flow sensor output was calibrated by a commercially available mass-flow controller. The catheter flow sensor was inserted into the airway of the rat to detect the airflow, and the four rod-shaped electrodes were used to obtain the ECG signals. The airflow waveforms were analyzed by discrete Fourier transform to obtain frequency spectra. Both results, the frequency spectra from the airflow and the ECG signals, were coincident, and the heartbeat signals decreased to 5.37 Hz from 7.08 Hz due to the inderal injection.