Simplified dual-lumen catheter design for simultaneous potentiometric monitoring of carbon dioxide and pH

Abstract

A novel dual-lumen catheter electrode design suitable for the simultaneous measurement of PCO2 (partial pressure of carbon dioxide) and pH in flowing blood is described. The probe is fabricated from a single segment of dual-lumen silicone rubber or polyurethane tubing that is impregnated with the proton ionophore tridodecylamine. The impregnation step imparts H+ permselectivity to both inner and outer walls of the tubing. By filling each lumen with a suitable buffer/electrolyte solution and Ag/AgCl reference electrode wire, simultaneous potentiometric detection of both PCO2 and pH is achieved. Careful optimization of incorporated proton carrier (tridodecylamine), plasticizer (o-nitrophenyl octyl ether), and lipophilic counteranion sites (tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) within the tubing walls yields catheter electrodes with resistance values of 10-20 M omega and relatively high stability in flowing blood. Results from continuous measurements of PCO2 and pH during long-term 30-65-h blood loop experiments demonstrate that, after an initial conditioning period, the catheter exhibits low drift rates (PCO2, 4.7 +/- 1.7 mV/30 h; pH, 1.4 +/- 0.5 mV/30 h) and yields continuously measured values in good agreement with those obtained on discrete samples with a commercial blood gas analyzer (PCO2, r2 = 0.997; pH, r2 = 0.915). In vivo evaluation of the catheter sensors, performed by implanting silicone rubber dual-lumen probes in the arteries of anesthetized dogs, indicates that the proposed catheter design can closely follow PCO2/pH changes induced in the animals during 6-13 h of continuous monitoring.

Response Characteristics of Anion-Selective Polymer Membrane Electrodes Based on Gallium(III), Indium(III) and Thallium(III) Porphyrins

“…EMF values were measured at ambient temperature (~22˚C) via a Macintosh IIcx computer with a NB-MIO-6X analog/digital input/output board (National Instruments, Austin, TX) and an electrode interface module (World Precision Instruments, Sarasota, FL) controlled by custom programmed LabView 2 software (National Instruments) as previously described. 35 Selectivity coefficients were calculated by the separate solution method using 0.01 M sodium salts solutions in 0.05 M 4-morpholinoethanesulfonic acid (MES) buffer, adjusted to pH 5.5 with NaOH. However, coefficients towards bicarbonate only were measured in 0.05 M 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid (EPPS) buffer adjusted to pH 8.5 with NaOH.…”

A Hydrogen Ion-Selective Sensor Based on Non-Plasticised Methacrylic-acrylic Membranes

“…Many polymer membranes that require less plasticisers compared with PVC were studied as sensing membrane for pH, e.g. polyurethane (Tecoflex) and silicon rubber (5,6) . To ensure that biocompatibility of the sensor is achieved, these membranes were further coated with antithrombogenic substances such as tridodecylmethylammonium heparinate complex or poly(ethylene oxide) (6,7) .…”

“…polyurethane (Tecoflex) and silicon rubber (5,6) . To ensure that biocompatibility of the sensor is achieved, these membranes were further coated with antithrombogenic substances such as tridodecylmethylammonium heparinate complex or poly(ethylene oxide) (6,7) . An obvious solution to the problem of non-biocompatibility caused by plasticiser is to eliminate the use of plasticiser altogether.…”

Determination of Low-Molecular-Weight Heparins and Their Binding to Protamine and a Protamine Analog Using Polyion-Sensitive Membrane Electrodes

“…Potentiometric responses of DNNS-based electrodes were measured against a miniature Ag/AgCl reference electrode (Bioanalytical Systems Inc., West Lafayette, IN), using a Macintosh IIcx computer and a data acquisition setup described previously (18). Sensors were calibrated by adding small aliquots of a standard protamine or [ϩ18RGD] solution (1 mg/ml) to 10 ml of a well-stirred sample solution.…”