Preliminary results of cervical impedance measurements
Thiago Kira de Souza Saito, Rafael Augusto Pedriali, Cinthia Mara Gabella, Maurício Chaves Junior, Elvio João Leonardo
Introduction: In this work, we report the development and initial tests of a measuring system that is used to measure the cervical electrical impedance with the purpose of assessing cervical ripening. The objective is to offer a system that provides real-time information about the cervical electrical impedance and, indirectly, of the cervical ripening with the aim of preventing premature birth.
Methods: Probes were developed and initial tests were performed. The probes used had electrodes that are far apart, with the assumption that in such cases deeper layers of the cervical tissue are measured.
Results: Preliminary measurements were performed in a single session on a non-gravid uterus, using as excitation signal a sinusoidal wave with frequency varying from 3 kHz to 100 kHz. Results indicate, as expected, that the magnitude of the impedance is inversely proportional to the frequency, indicating capacitive impedance.
Conclusion: Preliminary results were very encouraging. However, further measurements must be performed to correlate the impedance to the cervical ripening.
Analog Devices. Evaluation Board for the 1 MSPS 12-Bit Impedance Converter Network Analyzer, EVAL-AD5933EB - Preliminary Technical Data. Norwood: Analog Devices; 2007. 32 p.
Analog Devices. 1 MSPS, 12-Bit Impedance Converter, Network Analyzer, AD5933 - Datasheet. Norwood: Analog Devices; 2013. 40 p.
Avis NJ, Lindow SW, Kleinermann F. A preliminary investigation of electrical impedance measurements of the cervix as a method of monitoring and predicting the onset of labour. In Proceedings of the 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society; 1996 Oct 31-Nov 3; Amsterdam, Netherlands. Piscataway: IEEE; 1997. Vol. 2, p. 782-3. http://dx.doi.org/10.1109/IEMBS.1996.651974.
Blencowe H, Cousens S, Chou D, Oestergaard M, Say L, Moller A, Kinney M, Lawn J. Born too soon: the global epidemiology of 15 million preterm births. Reprod Health. 2013; 10(Suppl 1):S2-14. http://dx.doi.org/10.1186/1742-4755-10-S1-S2. PMid:24625129.
Bishop EH. Pelvic scoring for elective induction. Obstet Gynecol. 1964; 24(2):266-8. PMid:14199536.
Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Rouse DJ, Spong CY. Parturition. In: Cunningham F, Leveno K, Bloom S, Hauth J, Rouse D, Spong C. Williams obstetrics. 23rd ed. New York: McGraw-Hill; 2010. p. 136-72.
Danforth DN. The fibrous nature of the human cervix, and its relation to the isthmic segment in gravid and nongravid uteri. Am J Obstet Gynecol. 1947; 53(4):541-60. http://dx.doi.org/10.1016/0002-9378(47)90273-1. PMid:20291226.
Etemadi M, Chung P, Heller JA, Liu JA, Rand L, Roy S. Towards birth alert - a clinical device intended for early preterm birth detection. IEEE Trans Biomed Eng. 2013; 60(12):3484-93. http://dx.doi.org/10.1109/TBME.2013.2272601. PMid:23893706.
Fricke H, Morse S. The electrical resistance of blood between 800 and 4.5 million cycles. J Gen Physiol. 1925; 9(2):153-67. http://dx.doi.org/10.1085/jgp.9.2.153. PMid:19872239.
Gandhi SV, Walker DC, Brown BH, Anumba DOC. Comparison of human uterine cervical electrical Impedance measurements derived using two probes of different sizes tetra. Biomed Eng Online. 2006b; 5(62):1-7.
Gandhi SV, Walker DC, Milnes P, Mukherjee S, Brown BH, Anumba DOC. Electrical impedance spectroscopy of the cervix in non-pregnant and pregnant women. Eur J Obstet Gynecol Reprod Biol. 2006a; 129(2):145-9. http://dx.doi.org/10.1016/j.ejogrb.2005.12.029. PMid:16517044.
Hendrix NW, Chauhan SP, Morrison JC, Magann EF, Martin JN Jr, Devoe LD. Bishop score: a poor diagnostic test to predict failed induction versus vaginal delivery. South Med J. 1998; 91(3):248-52. PMid:9521363.
Hoe YSG, Gurewitsch ED, Shaahinfar A, Hu ES, Sampattavanich S, Ruffner M, et al. Measuring bioimpedance in the human uterine cervix: Towards early detection of preterm labor. In: Proceedings of the 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society; 2004 Sep 1-4; San Francisco, USA. Piscataway: IEEE; 2004. Vol. 1, p. 2368-72. http://dx.doi.org/10.1109/IEMBS.2004.1403686.
Jokhi RP, Brown BH, Anumba DOC. The role of cervical electrical impedance spectroscopy in the prediction of the course and outcome of induced labour. BMC Pregnancy Childbirth. 2009; 9(40):1-8. https://doi.org/10.1186/1471-2393-9-40. PMid:19725953.
Kleissl HP, Van Der Rest M, Naftolin F, Glorieux FH, De Leon A. Collagen changes in the human uterine cervix at parturition. Am J Obstet Gynecol. 1978; 130(7):748-53. http://dx.doi.org/10.1016/0002-9378(78)90003-0. PMid:637097.
O’Connell MP, Tidy J, Wisher SJ, Avis NJ, Brown BH, Lindow SW. An in vivo comparative study of the pregnant and nonpregnant cervix using electrical impedance measurements. Br J Obstet Gynaecol. 2000; 107(8):1040-1. http://dx.doi.org/10.1111/j.1471-0528.2000.tb10410.x. PMid:10955439.
Pandis GK, Papageorghiou AT, Ramanathan VG, Thompson MO, Nicolaides KH. Preinduction sonographic measurement of cervical length in the prediction of successful induction of labor. Ultrasound Obstet Gynecol. 2001; 18(6):623-8. http://dx.doi.org/10.1046/j.0960-7692.2001.00580.x. PMid:11844202.
Petersen LK, Oxlund H, Uldbjerg N, Forman A. In vitro analysis of muscular contractile ability and passive biomechanical properties of uterine cervical samples from nonpregnant women. Obstet Gynecol. 1991; 77(5):772-6. PMid:2014094.
Schwan HP. Electrical properties of tissue and cell suspensions. Adv Biol Med Phys. 1957; 5:147-209. http://dx.doi.org/10.1016/B978-1-4832-3111-2.50008-0. PMid:13520431.
Uldbjerg N, Ekman G, Malmstrom A, Olsson K, Ulmsten U. Ripening of the human uterine cervix related to changes in collagen, glycosaminoglycans, and collagenolytic activity. Am J Obstet Gynecol. 1983; 147(6):662-6. http://dx.doi.org/10.1016/0002-9378(83)90446-5. PMid:6638110.