Noninvasive and Minimally Invasive Multimodal Sensing for Continuous Cerebral Blood Flow Monitoring After TBI

One of the primary objectives of treatment for acute traumatic brain injury is to prevent subsequent ischemic injury. Reliable cerebral blood flow (CBF) monitoring is desirable for accurate clinical assessments and quick interventions, but existing tools can be complex to apply or available only intermittently. This study introduces two new multimodal approaches for relative CBF tracking based on simple sensing elements. In the first approach, sensors are used to augment an existing minimally-invasive intracranial catheter. In the second approach, sensors are worn non-invasively as a ring. Both consist of a photoplethysmogram blood volume sensor and a piezoelectric-based pressure sensor, which are used to capture local cerebral vascular resistance changes that are rarely available in the existing practice. Sensors are tested with (N=8) swine experiments in which multi-modal signals are collected, followed by data cleaning, feature extraction, and long short-term memory (LSTM) regression analysis to identify CBF information carried by intracranial and/or peripheral waveforms. Reference CBF measurements are collected by transcranial Doppler ultrasound. Results indicate that by combining the photoplethysmogram and piezoelectric sensing, a continuous relative CBF tracking method can be obtained. Alone or in combination, the proposed sensors demonstrate a better estimation of CBP changes than the cerebral perfusion pressure.