Tissue Oxygenation in Individuals with Spinal Cord Injury: A Pilot Study

Pressure injuries (PI) are debilitating tissue lesions characterised by slow healing and a high risk of severe infection. These injuries result from continued tissue hypoxia, or low tissue oxygen saturation (StO₂), which is a consequence of impaired blood circulation caused by continued pressure against tissue. PI result in significant suffering and a substantial financial burden. Therefore, we aim to develop an effective preventive measure. Persons with spinal cord injury (SCI) are at a high risk for PI due to their impaired mobility and lack of sensation to alert them to danger. The aim was to test the feasibility of an alert system based on StO₂ monitoring in persons with SCI using a novel textile-based near-infrared spectroscopy (NIRS) sensor.Sensors consisted of two emission and two detection points, each point comprising eight fibres each with three light-coupling bends. Textile integration of fibres was achieved by stitching on a mass-production stitching machine. Emission fibres were connected to LEDs of 740 nm and 810 nm. Detection fibres were connected to avalanche photodiodes. Sensors were attached to the skin in the high-PI-risk buttocks area covering the bony prominences of the ischial tuberosity. StO₂ was measured in three healthy subjects and two subjects with SCI during repeated sitting and pressure recovery phases.Our experiments showed decreases in StO₂ in both groups during sitting phases: during low-pressure sitting phases, StO₂ decreased on average -0.32%/min in the healthy subjects and at -1.24%/min in the SCI subjects. During high-pressure sitting, these rates increased to -1.16%/min for the healthy subjects and -2.16%/min for the SCI subjects. During recovery phases, StO₂ returned towards normal values, but did not always reach the initial baseline. No discomfort or skin irritation was observed.These first measurements show physiologically reasonable StO₂ values and demonstrate sufficient comfort while sitting on a sensor with no skin irritation or other adverse effects of sitting on the sensor for over 30 min. The nurses involved were satisfied with the easy-of-use, materials used, and patient safety demonstrated during the study. These results show that it is feasible to develop an alert system for PI prevention using a safe, wearable, textile-based NIRS sensor.