In-ear photoplethysmography for mobile cardiorespiratory monitoring and alarming

In this work, we report on human trials with the MedIT in-ear photoplethysmography (PPG) measurement system. The system is evaluated with healthy subjects and people suffering from heart insufficiency, respectively. Physiological heart activity can be measured with a minimal error of 1.2 heartbeats per minute and a regression coefficient of 0.9975 compared with standard ECG. Respiration related information was extracted by combining PPG amplitude analysis and car-diorespirational coupling (cardiorespiratory sinus arrhythmia). The moments of inspiration and expiration were estimated with a Naive Bayes' classifier with high sensitivity and specificity of 81,4% and 86%, respectively. For automatic cardiological alarming, a feature space is defined that clearly demonstrates the separability of normal heart rhythm and heart insufficiency. The results demonstrate a promising perspective for a mobile and long-term cardiorespiratory monitoring and alarming with an unobtrusive and inexspensive PPG measurement technique that is fully compatible to modern communication devices.