Management of COVID-19-related post-intubation tracheal stenosis.

Introduction: The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic has affected Italy since the beginning of 2020. Endotracheal intubation, prolonged mechanical ventilation, and tracheostomy are frequently required in patients with severe COVID-19. Tracheal stenosis is a potentially severe condition that can occur as a complication after intubation. The aim of this study was to evaluate the utility and safety of endoscopic and surgical techniques in the treatment of tracheal stenosis related to COVID-19. Materials and Methods: Between June 2020 and May 2022, consecutive patients with tracheal stenosis who were admitted to our surgical department were considered eligible for participation in the study. Results: A total of 13 patients were included in the study. They consisted of nine women (69%) and four men (31%) with a median age of 57.2 years. We included seven patients with post-tracheostomy tracheal stenosis. Bronchoscopy was performed to identify the type, location, and severity of the stenosis. All patients underwent bronchoscopic dilation and surveillance bronchoscopy at 7 and 30 days after the procedure. We repeated endoscopic treatment in eight patients. Three patients underwent tracheal resection anastomosis. Final follow-up bronchoscopy demonstrated no residual stenosis. Conclusions: The incidence of and risk factors associated with tracheal stenosis in critically ill patients with COVID-19 are currently unknown. Our experience confirms the efficacy and safety of endoscopic management followed by surgical procedures in cases of relapsed tracheal stenosis.

Chemotherapy-induced myasthenic crisis in thymoma treated with primary chemotherapy with curative intent on mechanical ventilation: a case report and review of the literature.

BACKGROUND: Thymoma is an uncommon cancer often associated with myasthenia gravis, an autoimmune disorder of the neuromuscular junction characterized by muscular fatigability. In patients with advanced nonmetastatic thymoma, primary chemotherapy may be required to induce tumor shrinkage and to achieve radical resection. Cancer chemotherapy has been anecdotally reported as a trigger factor for worsening of myasthenia gravis in thymic epithelial cancers. The study of uncommon cases of chemotherapy-related myasthenic crisis is warranted to gain knowledge of clinical situations requiring intensive care support in the case of life-threatening respiratory failure. CASE PRESENTATION: We report a case of an 18-year-old Caucasian woman with advanced Masaoka-Koga stage III type B2 thymoma and myasthenia gravis on treatment with pyridostigmine, steroids and intravenous immunoglobulins, who developed a myasthenic crisis 2 hours after initiation of cyclophosphamide/doxorubicin/cisplatin primary chemotherapy. Because of severe acute respiratory failure, emergency tracheal intubation, mechanical ventilation, and temporary (2 hours) discontinuation of chemotherapy were needed. Considering the curative intent of the multimodal therapeutic program, we elected to resume primary chemotherapy administration while the patient remained on mechanical ventilation. After 24 hours, the recovery of adequate respiratory function allowed successful weaning from respiratory support, and no further adverse events occurred. After 3 weeks, upon plasma exchange initiation with amelioration of myasthenic symptoms, a second course of chemotherapy was given, and in week 6, having documented partial tumor remission, the patient underwent radical surgery (R0) and then consolidation radiation therapy with 50.4 Gy in 28 fractions in weeks 15-20. CONCLUSIONS: This case report, together with the only four available in a review of the literature, highlights that chemotherapy may carry the risk of myasthenic crisis in patients affected by thymoma and myasthenia gravis. To our knowledge, this is the first reported case of chemotherapy continuation on mechanical ventilation in a patient with chemotherapy-induced myasthenic crisis requiring tracheal intubation. The lesson learned from the present case is that, in selected cases of advanced thymoma, the paradoxical worsening of myasthenia gravis during chemotherapy should not be considered an absolute contraindication for the continuation of primary chemotherapy with curative intent.

Stent en y autoexpandible para el tratamiento de la estenosis traqueobronquial maligna. Estudio retrospective / Self-expanding y stent for the treatment of malignant tracheobronchial stenosis. Retrospective study

El tratamiento paliativo de la estenosis traqueobronquial maligna es difícil. Las experiencias publicadas con stent en Y autoexpandibles son escasas, por lo que es necesario evaluar si los resultados que ofrecen son mejores que los de otras prótesis alternativas. Presentamos una serie retrospectiva de 20 pacientes consecutivos con estenosis traqueobronquial maligna, a los que se insertó un stent en Y metálico y recubierto. Las variables analizadas fueron las siguientes: alivio de la disnea, complicaciones y supervivencia. Los stent se insertaron a través de un traqueoscopio rígido en las 24h siguientes al ingreso del paciente, de forma segura y sin dificultades. Todos los pacientes lograron un alivio eficaz de la disnea y no se observaron efectos adversos, tempranos o tardíos, relacionados con el stent. La mortalidad a los 30 días fue del 40%, con una mediana de supervivencia de 12,2 semanas. La inserción de stent en Y autoexpandibles es un procedimiento seguro y eficaz para el tratamiento paliativo de la estenosis traqueobronquial maligna. En la actualidad, este es nuestro stent de elección para este subgrupo de pacientes

Palliation of malignant tracheobronchial stenosis is challenging. Published experience with self-expanding Y-shaped stents is limited and it seems necessary to evaluate whether they improve clinical results with respect to alternative prostheses. We present a retrospective case series of 20 consecutive patients with malignant tracheobronchial stenosis that underwent placement of a single-unit, Y-shaped covered metallic stent. Outcomes were: safety of the procedure, palliation of dyspnea, complications, and survival. All stents were safely and easily placed using a rigid tracheoscope within 24hours of admission. Dyspnea was effectively palliated in all patients, and no early or late adverse stent-related events were observed. Thirty-day mortality was 40%. Median survival was 12.2 weeks. Placement of Y-shaped self-expanding stents is a safe and effective procedure for the palliation of malignant tracheobronchial stenosis, and is currently our stent of choice for this subgroup of patients

Self-expanding y stent for the treatment of malignant tracheobronchial stenosis. Retrospective study. / Stent en y autoexpandible para el tratamiento de la estenosis traqueobronquial maligna. Estudio retrospectivo.

Palliation of malignant tracheobronchial stenosis is challenging. Published experience with self-expanding Y-shaped stents is limited and it seems necessary to evaluate whether they improve clinical results with respect to alternative prostheses. We present a retrospective case series of 20 consecutive patients with malignant tracheobronchial stenosis that underwent placement of a single-unit, Y-shaped covered metallic stent. Outcomes were: safety of the procedure, palliation of dyspnea, complications, and survival. All stents were safely and easily placed using a rigid tracheoscope within 24hours of admission. Dyspnea was effectively palliated in all patients, and no early or late adverse stent-related events were observed. Thirty-day mortality was 40%. Median survival was 12.2 weeks. Placement of Y-shaped self-expanding stents is a safe and effective procedure for the palliation of malignant tracheobronchial stenosis, and is currently our stent of choice for this subgroup of patients.

Mapping topographic structure in white matter pathways with level set trees.

Fiber tractography on diffusion imaging data offers rich potential for describing white matter pathways in the human brain, but characterizing the spatial organization in these large and complex data sets remains a challenge. We show that level set trees--which provide a concise representation of the hierarchical mode structure of probability density functions--offer a statistically-principled framework for visualizing and analyzing topography in fiber streamlines. Using diffusion spectrum imaging data collected on neurologically healthy controls (N = 30), we mapped white matter pathways from the cortex into the striatum using a deterministic tractography algorithm that estimates fiber bundles as dimensionless streamlines. Level set trees were used for interactive exploration of patterns in the endpoint distributions of the mapped fiber pathways and an efficient segmentation of the pathways that had empirical accuracy comparable to standard nonparametric clustering techniques. We show that level set trees can also be generalized to model pseudo-density functions in order to analyze a broader array of data types, including entire fiber streamlines. Finally, resampling methods show the reliability of the level set tree as a descriptive measure of topographic structure, illustrating its potential as a statistical descriptor in brain imaging analysis. These results highlight the broad applicability of level set trees for visualizing and analyzing high-dimensional data like fiber tractography output.

CONSISTENCY UNDER SAMPLING OF EXPONENTIAL RANDOM GRAPH MODELS.

The growing availability of network data and of scientific interest in distributed systems has led to the rapid development of statistical models of network structure. Typically, however, these are models for the entire network, while the data consists only of a sampled sub-network. Parameters for the whole network, which is what is of interest, are estimated by applying the model to the sub-network. This assumes that the model is consistent under sampling, or, in terms of the theory of stochastic processes, that it defines a projective family. Focusing on the popular class of exponential random graph models (ERGMs), we show that this apparently trivial condition is in fact violated by many popular and scientifically appealing models, and that satisfying it drastically limits ERGM's expressive power. These results are actually special cases of more general results about exponential families of dependent random variables, which we also prove. Using such results, we offer easily checked conditions for the consistency of maximum likelihood estimation in ERGMs, and discuss some possible constructive responses.

Characterization of multilocus linkage disequilibrium.

Linkage disequilibrium (LD) in the human genome, often measured as pairwise correlation between adjacent markers, shows substantial spatial heterogeneity. Congruent with these results, studies have found that certain regions of the genome have far less haplotype diversity than expected if the alleles at multiple markers were independent, while other sets of adjacent markers behave almost independently. Regions with limited haplotype diversity have been described as "blocked" or "haplotype blocks." In this article, we propose a new method that aims to distinguish between blocked and unblocked regions in the genome. Like some other approaches, the method analyses haplotype diversity. Unlike other methods, it allows for adjacent, distinct blocks and also multiple, independent single nucleotide polymorphisms (SNPs) separating blocks. Based on an approximate likelihood model and a parsimony criterion to penalize for model complexity, the method partitions a genomic region into blocks relatively quickly, and simulations suggest that its partitions are accurate. We also propose a new, efficient method to select SNPs for association analysis, namely tag SNPs. These methods compare favorably to similar blocking and tagging methods using simulations.