Wearable Cardiorespiratory Sensor for Real-Time Monitoring With Smartphone Integration

In this study, we propose a novel portable wearable cardiorespiratory sensor integrated with a smartphone, fabricated from plastic optical fiber (POF) and polydimethylsiloxane (PDMS) material. The sensor is designed for comprehensive cardiorespiratory monitoring, enabling accurate measurement of respiratory rate (BR), heart rate (HR), and HR variability (HRV). The prototype successfully captures heartbeat signals with excellent waveforms, revealing distinct BR and HR peaks in the frequency-domain plot. Our measurements show an average difference of 0.310 bpm for BR and 0.033 bpm for HR compared to reference values. Additionally, we performed 5-min HRV assessments under different conditions, yielding mean standard deviations of normal to normal (SDNN) of 52.87, 81.89, 49.41, and 28.22 ms for the control, specific breathing pattern, walking, and running groups, respectively. The cardiorespiratory sensor demonstrates its potential as a reliable alternative for daily monitoring of BR, HR, and HRV, offering versatility for various application scenarios with high safety and widespread usability.