With the development of medical technology, minimally invasive surgery has been widely used in clinical practice because of its small trauma and short recovery period. And in-vivo monitoring of pressure within the organ spaces can provide essential diagnostic information to help doctors guide the clinical treatment of diseases in minimally invasive surgery. Nevertheless, in early-stage, physicians have used catheters with external three-way drains to transmit BP (blood pressure) and ICP (intracranial pressure) to external sensors for measurement of saline or blood. The accuracy is vulnerable to the position of the patient during surgery.
This article presented a miniature and high-sensitivity micro-bubble F-P (Fabry-Perot) pressure sensor based on a cascade sensing structure of micro-bubble F-P cavity and FBG (fiber Bragg grating) has been proposed for invasive measuring the BP and ICP in minimally invasive surgery. Both fibers were chosen as silica materials leading to excellent biocompatibility. The tip micro-bubble F-P cavity was highly sensitive to pressure and thermal expansion, while the loosely arranged cascaded FBG is only sensitive to temperature. This configuration can realize pressure and temperature measurement at the same time without coupling effect, and effectively realize temperature compensation.
Experiments and analysis showed the optical fiber sensor has high-pressure sensitivity (8.93 pm/kPa) and temperature sensitivity (10.18 pm/℃) under constant pressure and temperature, and the relative error was less than 1.72%. Under the experimental verification, the full range error of the sensor after temperature compensation was reduced from 11.73% to 3.89%. In addition, the pressure measurement effect of the sensor in the clinical application was evaluated by an intracranial pressure test in live rats. The designed sensor showed excellent pressure dynamic response, and the in-vivo monitoring pressure was consistent with the clinical reference value.