On the Development of an Instrument for In-Line and Real-Time Monitoring of Blood-pH in Extracorporeal Circulation

The possibility of real-time monitor critical care analytes, such as pH, is recognized to provide relevant information for the diagnosis and treatment of a variety of disorders and would be of considerable support for the management of extracorporeal circulation (ECC). However, despite that blood pH can be measured from a long time by using electrodes or point-of-care instruments, such as blood-gas analyzers, costs, and complications associated with such measurement methods limit their use, thus, blood pH is generally not monitored during routinary ECC. In this article, we propose to exploit the tubing composing the ECC line to realize a low-cost and disposable pH-sensor and to interrogate such fluorescent sensors by using optical radiations. The proposed measuring system avoids complications related to blood sampling and may allow achieving single-patient cost requirements. Preliminary tests performed on a real ECC bloodline demonstrate that the system can operate with blood in ECC. Indeed, a 6-h ECC treatment simulated using bovine blood revealed a deviation with respect to the reference pH-meter typically of about a few thousandths pH and with a maximum of about 0.01 pH.