A sensorized face mask to monitor sleep and health of the astronauts: architecture definition, sensing section design and biosignals’ acquisition

Sleep can be classified into NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement) phases, forming cycles lasting 90-120 minutes. In this field, polysomnography (PSG) is the primary sleep diagnostic technique for sleep staging and sleep disorder diagnosis despite its limitations (e.g., lack of continuous monitoring and invasiveness). The research work proposes a mask-shaped wearable PSG device for astronauts to continuously and discretely monitor their sleep and health, aiming to improve sleep quality and duration. Notably, the mask discretely acquires multiple biosignals (i.e., EEG, ECG, PPG, eye movements, etc.) and jointly processes them to determine sleep stage and quality, as well as the user condition. This paper presents a literature overview of face-worn devices for sleep analysis and staging and of electrode or sensor placement to acquire PPG, ECG, and EEG signals. Then, the architecture of the face mask to be realized in the research project and the scouting results to determine the most optimal sensors or front-ends for each biosignal are presented. PPG, ECG, and inertial signals were acquired using the chosen sensors or front ends for each category, displaying good signal quality and accuracy. Thus, the optimal positioning of sensors and electrodes on the face to gather ECG, PPG, and inertial signals from the face was defined as fundamental for their integration into the sleep mask.