Sensitivity of a full-head coverage high-density time-resolved NIRS device to carotid compressions

Neuromonitoring during cardiac surgery helps prevent brain injury by detecting evidence of cerebral ischemia. Current neuromonitoring devices, such as cerebral oximeters, generally monitor one brain region, which prevents the detection of blood flow impairment in other vascular territories. A potential solution is to use a device with full-head coverage such as the newly developed high-density time-resolved NIRS system, Kernel Flow. This work aimed to assess Kernel Flow's sensitivity to regional cerebral oxygenation changes using momentary carotid compression (CC), a paradigm that causes substantial decreases in cerebral blood flow and oxyhemoglobin (HbO) throughout the ipsilateral hemisphere. Five healthy volunteers were imaged using a Kernel Flow headset during a 30-s CC. To assess the sensitivity of the device to regional changes, the number of good quality channels was compared between four brain regions: frontal, somatosensory, temporal, and occipital. HbO and deoxyhemoglobin (HbR) time series in the ipsilateral and contralateral hemispheres were analyzed. Overall, the frontal region had the largest amount of good-quality channels, and the ipsilateral regions showed the expected HbO decrease during CC. All contralateral regions showed minimal changes during CC, as expected. Overall, the Flow device showed good sensitivity to reduced cerebral blood flow; however, its use as a neuromonitor during cardiac surgery could be challenged by signal degradation due to hair, although this may be less of an issue with cardiac patients considering that most are older and have less hair.