For studies involving isolated or in situ perfused organs (heart, lung, liver, kidney) it is often important to continuously monitor pO2, pCO2 and/or pH of the perfusate. Which parameter is measured depends on the organ used and on the type of experiment conducted.
The universal perfusion solution monitor permits precise continuous or discontinuous measurement in liquid media of these three key parameters pO2, pCO2 and pH. The electrodes are all side stream flow-through electrodes and require a pulsation-free roller pump to deliver constant flow of perfusate through the electrode at flow rates in the range from 0.5 to 2 ml/min. The solution is split in parallel and pulled through each of the electrodes simultaneously. Therefore the total minute volume is a function of the flow rate and the number of electrodes used.
The pH sensor requires an external reference electrode (both the pO2 and pCO2 contain internal reference electrodes). For pH measurements one of two external reference electrodes are available; either the solid state leak free reference system or a KCl bridge (wet cell) reference system. The solid state leak free reference system is used whenever the perfusate must be recirculated or is required for further analysis. For applications using perfusate containing proteins like albumin it may be necessary to use the KCl bridge reference system for long term signal stability. Because of the high impedance of these sensors, screening or shielding of the measuring circuit is required to guard against electrostatic discharges and other electrical disturbances. The shielding cases also provide a convenient point of attachment to the multi-electrode mounting plate. The electrical signal produced by the electrodes is amplified by one of three PLUGSYS modules OPPM, pHMM or EMM for the O2, pH and CO2 electrodes respectively.