Analysis of measurement conditions for detecting change in vital signs with catheter flow sensor

We previously developed a catheter type flow sensor for measuring both breathing and heartbeat signals by analyzing the frequency of airflow signals in the airway during breathing (Kawaoka et al 2015 18th Int. Conf. on Solid- State Sensors, Actuators and Microsystems, Kawaoka et al 2015 IEEE Sensors, Kawaoka et al 2016 IEEE 29th Int. Conf. Micro Electro Mechanical Systems). In this study, we verified the optimized conditions for measuring heartbeat in the airway airflow and also confirmed during an animal experiment that the developed flow sensor can take measurements while following the change in the vital signs of rats. To obtain the necessary conditions for measuring the heartbeat, frequency analysis was performed using the airflow signals in the airway and measured with varying frequency resolutions. We experimentally confirmed that the heartbeat can be measured in the airflow when the frequency resolution is 1/10 or less of the basic breathing frequency. We also confirmed that the developed sensor could measure the changes in vital signs by administrating adrenaline and propranolol hydrochloride in experiments with rats.