Eliminating Flooding-related Issues in Electrochemical CO2-to-CO Converters: Two Lines of Defense.

By using silver (Ag) in nanostructured (nanowire, nanosphere, etc.) or thin-layer form as a catalyst for electrochemical CO2 reduction, very high CO-forming selectivity of almost 100% can be achieved. Supported by gas diffusion layers (GDLs),  the reactant CO2 in the gas phase can approach and potentially access active Ag sites, which allows current densities in the range of a few hundred mA cm-2 to be reached. Yet, the stability of gas diffusion electrode (GDE) based electrochemical CO2-to-CO converters is far from perfect, and the activity of GDE cathodes, especially when operated at high current densities, often significantly decays during electrolyses after no more than a few hours. The primary reason of stability losses in GDE-based CO2-to-CO electrolysers is flooding: that is, the excess wetting of the GDE that prevents CO2 from reaching Ag catalytic sites. In the past years, the authors of this paper at Empa and at the University of Bern, cooperating with other partners of the National Competence Center for Research (NCCR) on Catalysis, took different approaches to overcome flooding. While opinions differ with regard to where the first line of defense in protecting GDEs from flooding should lie, a comparison of the recent results of the two groups gives unique insight into the nature of processes occurring in GDE cathodes used for CO2 electrolysis.

Enhancing C≥2 product selectivity in electrochemical CO2 reduction by controlling the microstructure of gas diffusion electrodes.

We fabricate polymer-based gas diffusion electrodes with controllable microstructure for the electrochemical reduction of CO2, by means of electrospinning and physical vapor deposition. We show that the microstructure of the electrospun substrate is affecting the selectivity of a Cu catalyst, steering it from H2 to C2H4 and other multicarbon products. Specifically, we demonstrate that gas diffusion electrodes with small pores (e.g. mean pore size 0.2 µm) and strong hydrophobicity (e.g. water entry pressure >1 bar) are necessary for achieving a remarkable faradaic efficiency of ∼50% for C2H4 and ∼75% for C≥2 products in neutral 1M KCl electrolyte at 200 mA cm-2. We observe a gradual shift from C2H4 to CH4 to H2 during long-term electrochemical reduction of CO2, which we ascribe to hygroscopic carbonate precipitation in the gas diffusion electrode resulting in flooding of the Cu catalyst by the electrolyte. We demonstrate that even with minimal electrolyte overpressure of 50 mbar, gas diffusion electrodes with large pores (mean pore size 1.1 µm) lose selectivity to carbon products completely, suddenly, and irreversibly in favor of H2. In contrast, we find that gas diffusion electrodes with small pore size (mean pore size 0.2 µm) and strong hydrophobicity (water entry pressure ∼5 bar) are capable of resisting up to 1 bar of electrolyte overpressure during CO2RR without loss of selectivity. We rationalize these experimental results in the context of a double phase boundary reactivity, where an electrolyte layer covers the Cu catalyst and thus governs local CO2 availability. Our results emphasize the pivotal role of microstructure and hydrophobicity in promoting high C≥2 product selectivity and long-term stability in CO2RR flow cells.

A prospective study of pelvic floor dysfunctions related to delivery.

OBJECTIVE: To estimate the prevalence and impact on quality of life of urinary incontinence (UI) and anal incontinence (AI) three months after first delivery; to identify risk factors involved in UI or AI; to evaluate possible changes in sexual behaviour and anatomical modifications of pelvic floor after childbirth. STUDY DESIGN: A multicenter prospective study, in six Italian Ob/Gyn departments, of nulliparous women who delivered at term (37-42 weeks of gestation) between April and September 2005. A structured questionnaire investigated several maternal and obstetric variables. UI and AI were assessed by administration of the International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) and according to Wexner's Continence Grading Scale, at 2-3 days post-partum and at 3 months after delivery. Changes in sexual behaviour, and pelvic floor condition after delivery, were also recorded. Statistical analysis included comparison of means (Mann-Whitney or Student's t-test) and proportions (Chi-square test). Multiple logistic regression analysis was performed including variables that were significant in univariate comparisons. RESULTS: Of 960 enrolled women, 744 were evaluated 3 months after delivery and included in final analysis. The prevalences of UI and AI at that time were 21.6% and 16.3%, respectively. Onset of incontinence during pregnancy was an independent predictor for persistent UI (Odds Ratio (OR) 4.6, Confidence Interval (CI) 3.1-6.8, p<0.001) and AI (OR 3.6, CI 2.2-6.1, p<0.001). Family history of urinary or anal incontinence were respectively associated with UI (OR 2.6, CI 1.6-4.0, p<0.001) and AI (OR 2.4, CI 1.4-4.0, p<0.001) 3 months after delivery. Among obstetric factors, vaginal delivery was a strong risk factor for UI (OR 3.3, CI 2.0-5.3, p<0.001). The sexual score improved 3 months after delivery in 72.4% of women. Urogynaecological evaluation showed a significant association between grade 1-2 anterior prolapse, urethral hypermobility and UI. CONCLUSION: New onset of UI or AI during pregnancy, positive family history and vaginal delivery are independent risk factors for the persistence of symptoms of UI and AI in the early postpartum period. Adequate counselling and the implementation of targeted strategies to prevent or early identify these conditions are therefore mandatory to improve the patient's quality of life.

TVT SECUR System: Final results of a prospective, observational, multicentric study.

INTRODUCTION AND HYPOTHESIS: This is an observational multicentre prospective study into the complications and effectiveness of TVT SECUR™. METHODS: One hundred forty-seven patients with urodynamic or occult Stress Urinary Incontinence (SUI) were enrolled. Outcome measures at 6, 12 and 24 months were: objective cough test; subjective responses to PGI-S questionnaire and Visual Analogue Score. STATISTICAL ANALYSIS: Wilcoxon Test; Monte Carlo Exact Test. RESULTS: Ninety-five urodynamic SUI and 41 occult SUI patients were treated using transobturator (H-position) or retropubic (U-position) approach (110 vs. 26 patients). Cure rates at 6, 12, and 24 months were 87.5%, 88.6% and 89.5%. Failure rates at all follow-ups were similar for urodynamic and occult SUI. The U-position failure rate was comparable to H-position at short-term but significantly higher at mid-term. Familiarity with the technique brought significantly higher success rates. CONCLUSIONS: TVT SECUR is safe, effective and versatile, but has an appreciable learning curve.

Peri-operative morbidity and early results of a randomised trial comparing TVT and TVT-O.

The aim of this study was to compare the morbidity and short-term efficacy of retro-pubic (TVT) and inside-out trans-obturator (TVT-O) sub-urethral sling in the treatment of stress urinary incontinence. This was a prospective multi-centre randomised trial; 231 women with primary stress urinary incontinence were randomised to TVT (114) or TVT-O (117). The International Consultation on Incontinence-Short Form (ICIQ-SF), Women Irritative Prostate Symptoms Score (W-IPSS) and Patient Global Impression of Severity (PGI-S) questionnaires were used to evaluate the impact of incontinence and voiding dysfunction on QoL and to measure the patient's perception of incontinence severity. The primary and secondary outcome measures were rates of success and complications. The SPSS software was used for data analysis. The TVT-O procedure was associated with significantly shorter operation time and with a more extensive use of general anaesthesia when compared with TVT. There were 5 (4%) bladder perforations in the TVT group compared with none in the TVT-O group. Rates of early post-operative urinary retention and voiding difficulty were similar for both groups and no difference was found in the average hospital stay. Six patients (5%) in the TVT-O group complained of thigh pain in the post-operative course. The median follow-up time was 6 months. Two hundred eighteen patients were available for the analysis of outcomes. Subjective and objective cure rates were 92% and 92% in the TVT group and 87% and 89% in the TVT-O group. The ICIQ-SF questionnaire symptoms score showed a highly statistical decrease in both groups, the W-IPSS on the contrary was unchanged. Our data show that both procedures were equally effective in the short-term for the treatment of stress urinary incontinence with a highly significant improvement in incontinence-related QoL.

Porcine skin collagen implants to prevent anterior vaginal wall prolapse recurrence: a multicenter, randomized study.

PURPOSE: We evaluated the efficacy of the Pelvicol porcine collagen implant for preventing recurrent anterior vaginal wall prolapse in women undergoing primary surgery for pelvic organ prolapse. MATERIALS AND METHODS: This was a prospective, randomized, multicenter trial in 206 women with stage II or greater anterior vaginal wall prolapse (point Ba -1 or greater) according to the pelvic organ prolapse quantification system. The patients were randomly assigned to undergo anterior vaginal repair or the same procedure with Pelvicol implant reinforcement. SPSS software was used for data analysis. RESULTS: A total of 201 women were available for surgical outcome analysis, including 98 and 103 in the implant and no implant groups, respectively. All completed the 1-year followup visit. Most women were satisfied with the postoperative condition with a significant decrease in the visual analog scale score in each group (p <0.001). Anatomical anterior recurrence (point Ba greater than -1) was observed in 7 women (7%) in the implant group and in 20 (19%) in the other groups (OR 3.13, 95% CI 1.26-7.78, p = 0.019). Additionally, there were 11 women (3 and 8, respectively, or 5%) with posterior recurrence and 6 (3 per group or 3%) with unsatisfactory results at the upper vaginal segment. One patient who received a porcine implant had vaginal extrusion of the mesh 1 month after surgery. CONCLUSIONS: Our data show that the Pelvicol implant can be easily and readily used to augment and reinforce anterior colporrhaphy. The prolapse recurrence rate was considerably lower in the implant group compared with outcomes in patients treated with simple anterior repair.

Tension-free vaginal tape (TVT) and intravaginal slingplasty (IVS) for stress urinary incontinence: a multicenter randomized trial.

OBJECTIVE: This study was undertaken to compare the efficacy and morbidity of 2 minimally invasive procedures for stress urinary incontinence. STUDY DESIGN: This was a prospective randomized multicenter trial; 190 women with primary urodynamic stress incontinence were randomly assigned to tension-free vaginal tape (TVT) (n = 95) or intravaginal slingplasty (IVS) (n = 95). The primary and secondary outcome measures were rates of success and complications. SPSS software was used for data analysis. RESULTS: At 2 years 92 and 87 patients were available in the TVT and IVS group for outcomes analysis. Subjectively, 80 (87%) and 68 (78%) women were cured, respectively. Objectively, a 1-hour pad test was negative in 78 (85%) and 63 (72%) patients. Eight of the patients assigned to IVS (9%) had vaginal erosion/infection, compared with none in the TVT group (P < .01). CONCLUSION: Both procedures were effective for stress incontinence, but 9% of women treated with the IVS required removal of the tape for erosions.

New trends in the surgical treatment of outlet obstruction: clinical and functional results of two novel transanal stapled techniques from a randomised controlled trial.

BACKGROUND AND AIMS: A randomised trial was undertaken to compare the clinical and functional results of two novel transanal stapled techniques in patients with outlet obstruction syndrome. MATERIALS AND METHODS: Ninety-six females with outlet obstruction were treated with medical therapy and biofeedback for 2 months; 67 non-responders were evaluated by the Constipation Scoring and Continence Grading Systems, clinical examination, endoscopy, dynamic defecography, anorectal manometry, transanal ultrasound and anal EMG, and 50 of them, all affected with descending perineum, intussusception and rectocele, were randomly assigned to two groups and operated on: 25 patients (mean age 53.2+/-15.3 years) underwent a single Stapled Trans-Anal Prolapsectomy, associated with Perineal Levatorplasty (STAPL Group), and the other 25 (mean 54.6+/-14.2 years) underwent a double Stapled Trans-Anal Rectal Resection (STARR Group). Patients were followed-up for a mean period of 23.4+/-5.1 months in STAPL Group and 22.3+/-4.8 in STARR Group. RESULTS: STARR Group showed a significantly (p<0.0001) lower pattern of postoperative pain and a greater decrease (P=0.0117) of the rectal sensitivity threshold volume; otherwise, no differences were found in operative time, hospital stay, or time of inability to work. Complications included delayed healing of the perineal wound (ten), dyspareunia (five), urinary retention (two) and stenosis (one) in STAPL Group, and urge to defecate (four), transitory incontinence to flatus (two), urinary retention (two), bleeding (one) and stenosis (one) in STARR Group. All constipation symptoms significantly improved without worsening of anal continence and with excellent/good outcome at 20 months in 76 and 88% of patients of STAPL Group and STARR Group, respectively. Seven patients of STAPL Group had a little residual rectocele, while both intussusception and rectocele were corrected in all patients of STARR Group. Neither operation modified anal pressures or caused lesions of anal sphincters. CONCLUSIONS: Both techniques are safe and effective in the treatment of outlet obstruction; nevertheless, the double Stapled Trans-Anal Rectal Resection seems to be preferable due to less pain, absence of dyspareunia, reduced rectal sensitivity threshold volume and absence of residual rectocele at defecography.