Figure 2:

Clinical system to monitor TBI patients in ITU

a: Schematic of microfluidic platform layout. b: Top photograph shows an electrocorticography strip electrode (ECoG), the microdialysis probe and the intracranial pressure (ICP) probe which are inserted into human brain tissue during a craniotomy. Bottom photograph depicts use in King’s College Hospital ITU. The dotted blue line shows where a length of fine-bore tubing connects the implanted microdialysis probe to the analysis system. c: An example potassium calibration carried out during TBI monitoring in the hospital. Dialysate measurements are indicated by blue bars and multi-point calibration by purple bars. Concentrations are 10.0, 2.70, 6.35 and 10.0 mM (levels indicated by dotted lines). This is an expanded view of the calibration highlighted by a yellow box in (e). d: Removal of air bubble in chip using the larger capacity flow module. An air bubble caused a sudden decrease in the signal-to-noise ratio of a sample perfused at 2 μl/min. PBS was flushed through the system at 10 μl/min on top of the glucose flow for 20 seconds, removing the air bubble and the signal returned to the same level. e: Clinical automatic calibration example in TBI patient monitoring. Potassium (purple), glucose (red) and lactate (green) sensors were continually analysing dialysate (blue boxes) in between programmed calibration cycles (purple boxes). Known standards were introduced every 3 h (glucose: 0.0, 2.0, 1.0 mM, lactate: 1.0, 0.0, 0.5 mM, potassium: 10.0, 2.70, 6.35 mM). The changes in potassium and lactate seen at around 3 h are not artefactual but possibly represent a pathophysiological event that is not picked up by other monitoring modalities.