Multi-wavelength SPAD photoplethysmography for cardio-respiratory monitoring

There is a growing interest in photoplethysmography (PPG) for the continuous monitoring of cardio-respiratory signals by portable instrumentation aimed at early diagnosis cardiovascular diseases. In this context, it conceivable that PPG sensors working different wavelengths simultaneously can optimize identification apneas and quantification associated heart-rate changes or other parameters depend on shape (e.g., systematic vascular resistance pressure), when evaluating severity breathing disorders during sleep general health monitoring. Therefore, objective work to present novel pulse oximeter provides synchronous data logging related three light (green, red, infrared) transmission mode both heart rate measurements reliable assessment oxygen saturation. The considered more robust over motion artifacts than reflection mode, but current oximeters cannot employ green due high absorbance body tissues wavelength. For reason, our device based Single-Photon Avalanche Diode (SPAD) with very short deadtime (less 1 ns) have, same time, single photon sensitivity high-count allows acquiring all site mode. Previous studies have shown SPAD cameras be used measuring through remote PPG, saturation measures contact SPAD-based never been addressed so far. results preliminary validation six healthy volunteers reflect expected physiological phenomena, providing rms errors Inter Beat Interval estimation smaller 70 ms (with light) maximum error 1% apneas. Our prototype demonstrates reliability devices long-term variables as an alternative photodiodes especially minimal area optical power are required.