Do salivary bypass tubes lower the incidence of pharyngocutaneous fistula following total laryngectomy? A retrospective analysis of predictive factors using multivariate analysis

Salivary bypass tubes (SBT) are increasingly used to prevent pharyngocutaneous fistula (PCF) following laryngectomy and pharyngolaryngectomy. There is minimal evidence as to their efficacy and literature is limited. The aim of the study was to determine if SBT prevent PCF. The study was a multicentre retrospective case control series (level of evidence 3b). Patients who underwent laryngectomy or pharyngolaryngectomy for cancer or following cancer treatment between 2011 and 2014 were included in the study. The primary outcome was development of a PCF. Other variables recorded were age, sex, prior radiotherapy or chemoradiotherapy, prior tracheostomy, type of procedure, concurrent neck dissection, use of flap reconstruction, use of prophylactic antibiotics, the suture material used for the anastomosis, tumour T stage, histological margins, day one post-operative haemoglobin and whether a salivary bypass tube was used. Univariate and multivariate analysis were performed. A total of 199 patients were included and 24 received salivary bypass tubes. Fistula rates were 8.3% in the SBT group (2/24) and 24.6% in the control group (43/175). This was not statistically significant on univariate (p value 0.115) or multivariate analysis (p value 0.076). In addition, no other co-variables were found to be significant. No group has proven a benefit of salivary bypass tubes on multivariate analysis. The study was limited by a small case group, variations in tube duration and subjects given a tube may have been identified as high risk of fistula. Further prospective studies are warranted prior to recommendation of salivary bypass tubes following laryngectomy

Integration of Data Assimilation Techniques in Geomechanical Modelling: Ensemble Smoother with Multiple Data Assimilation Analysis

The use of Data Assimilation (DA) techniques is receiving an increasing interest in geomechanical applications, with the aim to assess and reduce uncertainties associated to numerical outcomes by model constrain with available measurements. In geomechanical simulations, ensemble-based DA approaches are usually preferred. Among such techniques, Ensemble Smoother with Multiple Data Assimilation (MDA-ES) is usually recognized to improve the outcomes in nonlinear problems, but its use and parameter definition is still object of research. In this paper, MDA-ES has been tested in a synthetic case study dealing with the prediction of land subsidence above a producing hydrocarbon reservoir. Its effectiveness has been investigated varying both the DA parametrization and the geomechanical properties