A system for determining at least one physiological parameter based on a vascular blood flow and/or volume characteristics related to a thoracic bone or septum of a subject. The system comprises a sensor for skin apposition. The sensor comprises at least one light source for illuminating of the thoracic bone or septum and a detector for measuring of reflected light from the thoracic bone or septum. The system further includes a control unit configured to control operation of the sensor and an analysing unit configured to analyse the measurement data for determining the at least one physiological parameter
