Toward Patient-specific Pessary to Manage Pelvic Organ Prolapse: Design and Simulation.

This study proposed a novel design and personalized approach to developing an intra-vaginal device, also known as a pessary, for the treatment of Pelvic Organ Prolapse (POP). Although POP is likely to have a more diverse dynamic than other health conditions in women, it is currently treated as a "one-shape-fits-all" problem in all cases. Pessaries are conservative devices inserted into the vagina to support its internal structure and predominantly come in a ring shape design. Failure rates as high as 50% within the first year of use have been attributed to the poor design of these pessaries; with symptoms such as irritation, bleeding, and lacerations felt by most users. To address this problem, a new base shape design was proposed and its deformation was examined using Finite Element Analysis (FEA). Based on the anatomical measurements of each patient, the base design can be adjusted accordingly. To demonstrate the effectiveness of the proposed design, a comparative study was conducted with the most commonly used support pessary, also known as the ring pessary. In order to model the large deformation of the pessaries, the hyperelastic constitutive law (Yeoh model) was fitted to the available stress-strain data of SIL 30 (a silicone urethane resin supplied by Carbon Inc.). The results showed that re-directing the reaction forces of the pessary towards the lateral walls, supported by the pelvic bones, could decrease the overall displacement of the pessaries, and provide effective symptomatic relief thereby, delaying or preventing surgical procedures.Clinical relevance- There is a clear clinical need to develop a more effective conservative therapy for managing POP. The personalized pessaries proposed in this paper can be an effective method for providing symptomatic relief and avoiding displacement, compared to the currently available devices on the market. Made-to-measure for each patient, the devices are anatomically suited and can be adjusted throughout a patient's treatment plan to allow for higher compliance and overall success rate.

Effect of magnesium sulfate and nifedipine on the risk of developing pulmonary edema in preterm births.

OBJECTIVE: To evaluate the risk of developing pulmonary edema in women exposed to nifedipine, magnesium sulfate (MgSO4), or both in a preterm setting. STUDY DESIGN: We carried out a retrospective case-control study at a large tertiary care center from 2007 to 2012. Cases of pulmonary edema were age, and gestational age matched to controls at a ratio of 1 case to 4 controls. Logistic regression analysis was used to estimate the effect of nifedipine and/or MgSO4 on the development of pulmonary edema while controlling for predetermined confounding variables. Stepwise logistic regression analysis was used to evaluate additional risk factors of pulmonary edema. RESULTS: A total of 150 charts were reviewed (28 cases and 122 controls). Nifedipine did not increase the odds of developing pulmonary edema [adjusted odds ratio (OR)=1.22 (confidence interval (CI) 0.50, 3.01), P=0.67], whereas exposure to MgSO4, or both MgSO4 and nifedipine, significantly increased the risk of developing pulmonary edema [adjusted OR=3.91 (CI 1.44, 10.65), P=0.008 and adjusted OR=4.75 (CI 1.15, 19.71), P=0.032, respectively]. In the stratified analysis, this association persisted even in nonpreeclamptic women [nifedipine: adjusted OR=0.91 (CI 0.33, 2.52), P=0.852; MgSO4: adjusted OR=3.51 (CI 1.26, 9.76), P=0.016; both: adjusted OR=3.39 (0.76, 15.07), P=0.108]. Other independent risk factors for pulmonary edema were multi-fetal pregnancy, azithromycin, and erythromycin administration. CONCLUSION: MgSO4 treatment is strongly associated with the development of pulmonary edema when used either as a tocolytic agent or for seizure prophylaxis. In light of the availability of safer alternatives, MgSO4 should be used for tocolysis only in cases whereby the benefits clearly outweigh the risks.