Simplified dual-lumen catheter design for simultaneous potentiometric monitoring of carbon dioxide and pH.
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.
Telting-Diaz
M
M
Department of Chemistry, University of Michigan, Ann Arbor 48109.
Collison
M E
ME
Meyerhoff
M E
ME
D000818:Animals; D001784:Blood Gas Analysis / Q000295:instrumentation*; D002138:Calibration; D002245:Carbon Dioxide / Q000097:blood*; D002408:Catheters, Indwelling; D002417:Cattle; D004285:Dogs; D006863:Hydrogen-Ion Concentration
D002245:Carbon Dioxide