Wednesday  |  Carnegie III  |  10:00 AM–10:20 AM

#13663, Time-dependent Deformation of Vaginal Tissue Under Inflation

Women who undergo Cesarean deliveries are at higher risk of certain maternal morbidities on subsequent pregnancies. The US has one of the highest Cesarean rates in the world, with a rate double what has been estimated necessary. This is exacerbated by the lack of scientific-based universal standards for when Cesarean deliveries are recommended. Knowledge of the viscoelastic behavior of vaginal tissue could lead to new methods of identifying safe vaginal delivery. In this study, we use free-extension inflation to examine the biaxial creep behavior of rat vaginal tissue.

The vaginal canals of adult virgin female rats were isolated via dissection. Specimens (n=12) were mounted onto two needles as described in [1]. Specimens were then loaded into an inflation setup and preconditioned for 20 cycles to 150% of the initial volume, then allowed to rest for 10 minutes. Specimens were then inflated with phosphate buffered saline to 4 psi for 50 minutes (first creep), then 8 psi for 50 minutes (second creep), then 12 psi for 50 minutes (third creep). Two cameras (Basler ace acA2440-75um, Basler Inc., Exton, PA) captured images during testing, and digital image correlation (DIC) software (Vic-3D, version 9, Correlated Solutions, Columbia, SC) was used to calculate the normal axial Lagrangian strains in the longitudinal (LD) and circumferential (CD) directions.

Through all creep tests, significantly more strain occurred in the CD than in the LD. In the LD, significantly more strain occurred in the first creep (0.0039±0.0007) than in the second (0.0019±0.0003) or third (0.0018±0.0002). Likewise in the CD, significantly more strain occurred in the first creep (0.0079±0.0012) than in the second (0.0043±0.0004) or third (0.0048±0.0005).

This abstract presents the first DIC measurements of strain of vaginal tissue during biaxial inflation creep tests. Results indicate that vaginal tissue exhibits nonlinear viscoelastic behavior since the change in strain over time decreased in the later creep phases, even though the intraluminal pressure increased. Future constitutive models will need to account for the nonlinear viscoelasticity of the vaginal tissue to predict the deformations of the vagina during delivery.

This work was supported by NSF Grant No. 1929731

References: 1. McGuire, J. et al., 2019, Interface Focus, 9(4), p.20190029

Justin Dubik   Virginia Tech
Alfonsina Tartaglione   Università degli Studi della Campania “Luigi Vanvitelli”
David Dillard   Virginia Tech
Raffaella De Vita   Virginia Tech