The Real-Time Estimation of Respiratory Flow and Mask Leakage in a PAPR Using a Single Differential-Pressure Sensor and Microcontroller-Based Smartphone Interface in the Development of a Public-Oriented Powered Air-Purifying Respirator as an Alternat

In this study, a prototype system was developed as a potential alternative to lockdown measures against the spread of airborne infectious diseases such as COVID-19. The system integrates real-time estimation functions for respiratory flow and mask leakage into a low-cost powered air-purifying respirator (PAPR) designed for the general public. Using only a single differential-pressure sensor (SDP810) and a controller (Arduino UNO R4 WiFi), the respiratory flow (<b><i>Q</i>_3e</b>) is estimated from the differential pressure (<b>Δ<i>P</i></b>) and battery voltage (<b>V_b</b>), and both the wearing status and leak status are transmitted to and displayed on a smartphone application. For evaluation, a testbench called the Respiratory Airflow Testbench was constructed by connecting a cylinder-piston drive to a mannequin head to simulate realistic wearing conditions. The estimated respiratory flow <b><i>Q</i>_3e</b>, calculated solely from <b>Δ<i>P</i></b> and <b>V_b</b>, showed high agreement with the measured flow <b><i>Q</i>_3m</b> obtained from a reference flow sensor, confirming the effectiveness of the estimation algorithm. Furthermore, an automatic leak detection method based on the time-integrated value of <b><i>Q</i>_3e</b> was implemented, enabling the detection of improper wearing. This system thus achieves respiratory flow estimation and leakage detection based only on <b>Δ<i>P</i></b> and <b>V_b</b>. In the future, it is expected to be extended to applications such as pressure control synchronized with breathing activity and health monitoring based on respiratory and coughing analysis. This platform also has the potential to serve as the foundation of a PAPR Wearing Status Network Management System, which will contribute to societal-level infection control through the networked sharing of wearing status information.