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Research Papers

# Direct Measurement of the Permeability of Human Cervical Tissue

[+] Author and Article Information
Michael Fernandez

Deptarment of Mechanical Engineering,
Columbia University,
New York, NY 10027
e-mail: mjf2152@columbia.edu

Joy Vink

Assistant Clinical Professor
Department of Obstetrics and Gynecology,
Columbia University Medical Center,
New York, NY 10032
e-mail: jyv2101@columbia.edu

Kyoko Yoshida

Department of Mechanical Engineering,
Columbia University,
New York, NY 10027
e-mail: ky2218@columbia.edu

Ronald Wapner

Vice Chairman for Research
Department of Obstetrics and Gynecology,
Columbia University Medical Center,
New York, NY 10032
e-mail: rw2191@columbia.edu

Kristin M. Myers

Assistant Professor
Department of Mechanical Engineering,
Columbia University,
New York, NY 10027
e-mail: kmm2233@columbia.edu

1Corresponding author.

Contributed by the Bioengineering Division of ASME for publication in the JOURNAL OF BIOMECHANICAL ENGINEERING. Manuscript received October 3, 2012; final manuscript received January 4, 2013; accepted manuscript posted January 18, 2013; published online February 7, 2013. Editor: Victor H. Barocas.

J Biomech Eng 135(2), 021024 (Feb 07, 2013) (8 pages) Paper No: BIO-12-1462; doi: 10.1115/1.4023380 History: Received October 03, 2012; Revised January 04, 2013; Accepted January 18, 2013

## Abstract

The mechanical integrity of the uterine cervix is critical for a pregnancy to successfully reach full term. It must be strong to retain the fetus throughout gestation and then undergo a remodeling and softening process before labor for delivery of the fetus. It is believed that cervical insufficiency (CI), a condition in pregnancy resulting in preterm birth (PTB), is related to a cervix with compromised mechanical strength which cannot resist deformation caused by external forces generated by the growing fetus. Such PTBs are responsible for infant developmental problems and in severe cases infant mortality. To understand the etiologies of CI, our overall research goal is to investigate the mechanical behavior of the cervix. Permeability is a mechanical property of hydrated collagenous tissues that dictates the time-dependent response of the tissue to mechanical loading. The goal of this study was to design a novel soft tissue permeability testing device and to present direct hydraulic permeability measurements of excised nonpregnant (NP) and pregnant (PG) human cervical tissue from women with different obstetric histories. Results of hydraulic permeability testing indicate repeatability for specimens from single patients, with an order of magnitude separating the NP and PG group means ($2.1 ± 1.4×10-14$ and $3.2 ± 4.8×10-13m4/N·s$, respectively), and large variability within the NP and PG sample groups. Differences were found between samples with similar obstetric histories, supporting the view that medical history may not be a good predictor of permeability (and therefore mechanical behavior) and highlighting the need for patient-specific measurements of cervical mechanical properties. The permeability measurements from this study will be used in future work to model the constitutive material behavior of cervical tissue and to develop in vivo diagnostic tools to stage the progression of labor.

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## Figures

Fig. 1

Permeability experiment overview. A soft tissue specimen is placed between two porous supports while a constant fluid pressure gradient is applied. Flow is measured downstream using time-lapse images of dye as it is displaced inside a capillary tube.

Fig. 2

A typical plot of dye progression over the course of a cervical tissue permeation test for a PG specimen. The visible straightening of the curve signifies steady-state conditions.

Fig. 3

Permeability versus pregnancy state (semilog plot; PG = pregnant, NP = nonpregnant). Each cross or circle represents the average (mean) of all specimen permeability measurements from a single patient. Error bars represent the minimum and maximum measured permeability values (range) for a given cervix sample.

Fig. 4

(a) Nonpregnant permeability versus gravida (number of pregnancies). (b) Nonpregnant permeability versus number of prior vaginal births (linear plot). There was not enough obstetric information to include specimen NP5 in panel B. Each point represents the mean permeability from all specimens from a given patient. The error bars represent the minimum and maximum measured permeability values (range) for a given patient.

Fig. 5

Mean hydraulic permeability of the specimens for each pregnant patient versus gestation time at hysterectomy. Each data point is the mean permeability across all specimens from a given patient. Error bars represent the minimum and maximum measured permeability values for a given cervix sample.

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