SILVER SILVER CHLORIDE ELECTRODES FOR MEASUREMENT OF POTENTIAL DIFFERENCE IN HUMAN BRONCHI/

Background-An easy and reliable method to measure potential difference (PD) in the lower airways would be of interest in the field of cystic fibrosis. We have developed silver/silver chloride (Ag/ AgCl) electro des to measure PD in the lower airways. Methods-To validate this techn ique the nasal PD measured with Ag/AgCl electrodes and with convention al perfused electrodes was compared in 16 patients. The range of PD me asured with Ag/AgCl electrodes in the lower airways during fibreoptic bronchoscopy was determined in 14 adult patients and in nine the repro ducibility of this technique was examined. Results-Nasal PD values mea sured with Ag/AgCl and perfused electrodes were highly correlated (r = 0.985, p<0.0001) and the limits of agreement (mean +/-2SD of the diff erence) between the two methods were -1.91 mV and 1.53 mV. In the lowe r airways a progressive and slight decrease in PD values with decreasi ng airway diameter was observed in most patients. The mean (2SD) of th e differences between the two tracheal measurements was 0.21 (1.73) mV . Conclusions-The use of Ag/AgCl electrodes gives a reliable and repro ducible measurement of PD in the lower airways in humans.