The Single Field method uses a primary pair of excitation electrodes with the positive electrode located at the proximal end of the measurement area and the negative electrode located at the distal end of the measurement area to generate an electrical field in the heart. The change in conductance as the blood pool volume changes is measured by a single pair of sensing electrodes between the pair of excitation electrodes. Single field catheters can be quickly identified by the uniform spacing of the two pairs of electrodes over the entire length of the measurement area, and are usually Two French or smaller in size. Single Field catheters are also known as single segment catheters, and are normally used in small animal models such as rodents.
The Dual Field method also uses a primary pair of excitation electrodes with the positive electrode located at the proximal end of the measurement area and the negative electrode located at the distal end of the measurement area. An additional secondary pair of excitation electrodes are placed on the catheter next to the primary pair of electrodes. The secondary positive electrode is located at the distal end of the measurement area (but proximal to the primary negative electrode) and the secondary negative electrode is located at the proximal end of the measurement area (but distal to the primary positive electrode). These secondary electrodes create a second electrical field of opposite polarity which serves to expand the primary field to create a more uniform electrical field over the length of the measurement area.
The change in conductance as the blood pool volume changes is then measured by multiple pairs of sensing electrodes, each of these pairs is known as a segment. The signals from these segments (there are normally seven) are then summed together for the total volume signal. Dual field catheters can be quickly identified by the group of five or six closely spaced electrodes at either the proximal or distal end of the measurement area, and are also known as multiple segment catheters. Dual Field catheters are normally used in large animal models such as pigs, and are Three French or larger in size.
For further technical assistance with this or any other issue, please contact ADInstruments Technical Support by clicking HERE.