Measuring bioimpedance in the human uterine cervix: towards early detection of preterm labor.
We have created a bioimpedance probe designed to detect subtle changes in human cervical tissue composition in vivo, and thereby detect the onset of cervical remodeling in a noninvasive manner sooner than existing clinical methods allow. Our cervical bioimpedance measurement device, which can be used during a routine pelvic examination, is composed of a contoured probe with disposable tip and, within the probe's handle, a bioimpedance sensor equipped with an integrated chip capable of generating sinusoidal voltage of varying frequencies. A constant force spring assures consistent measurements through a range of contact forces applied. An activation switch allows the operator to control the application of current. The sensor can be synchronized with a computer data storage and analysis system, which interfaces with the device. With the probe placed in contact with a collagen gels of varying concentration, the relationship between measured bioimpedance and collagen concentration is verified to be positive exponential (R/sup 2/=0.94) and repeatability in saline solution showed that measurements varied by less than +/-10% over 20 trials. Finally, a variety of user-applied forces showed that impedance values plateau when forces exceed 1N.
Hoe
Y S G
YS
Dept. of Biomed. Eng., Johns Hopkins Univ., Baltimore, MD, USA.
Gurewitsch
Edith D
ED
Shaahinfar
A
A
Hu
Elbert S
ES
Sampattavanich
Somponnat
S
Ruffner
Melanie
M
Ching
Kenny H S
KH
Allen
Robert H
RH