1,720,980 research outputs found
A procedure for the autonomic diagnosis of esophageal motor disorders from HRM data processing
Full text linkA proper understanding of physiological mechanisms for the propulsion of ingested food within the gastrointestinal canal is mandatory for the diagnosis of pathologies affecting its motility. One of the most discussed regions within the digestive system is the esophagus, as a tubular structure whose function pertains to bring food from mouth to stomach by means of a precise sequence of longitudinal and circumferential muscular contractions, called peristalsis. Pathologies and degenerative phenomena may influence this mechanism, leading to chest pain, acid reflux, cancer development and/or inability to swallow. As a growing number of subjects suffer from esophageal motility disorders, it represent a relevant social-health problem.
The diagnosis of esophageal motility disorders is actually performed by analyzing results from High Resolution Manometry (HRM), the gold standard in esophageal diagnostics. HRM consists in a clinical test designed to measure the pressure evolution over time at different positions within a duct by means of a special probe. A number of models have been proposed in literature to interpret data from HRM, but results are often inadequate because of an improper evaluation of the complex esophageal conformation and the corresponding heterogeneous distribution of physio-mechanical properties. Furthermore, an inadequate effort was made to identify relationships between model parameters and esophageal properties, and their identification was usually performed accounting for limited sets of experimental data. The guidelines in diagnosis of esophageal motility disorders are currently defined by the Chicago Classification: a hierarchical algorithm that accounts for specific parameters evaluated by analyzing HRM results. The main drawback in this procedure pertains to the requirement of specialized experts for the evaluation of such parameters, inducing intra- and inter-operator variabilities with regard to the final diagnosis.
The esophageal motility was investigated with the goal of providing a physiological model able to interpret results from HRM, accounting for parameters related to specific physio-mechanical properties of the esophagus and their heterogeneous distribution. Activities were focused on the implementation of a procedure for the autonomic detection of esophageal motility dysfunctions based on HRM measurements processing. As a result, objective criteria were defined to support the medical staff during the traditional diagnostic activity of esophageal motility disorders.
The physiological model was developed to this purpose to evaluate the pressure distribution due to the transit of a generic pressure wave. The corresponding optimal sets of model parameters were identified accounting for the HRM results of each subject of a training set composed by 229 patients and 35 healthy volunteers. Patients and volunteers were classified into groups according to their specific healthy or pathological conditions, as non-pathological (73 patients and 35 volunteers), Achalasia pattern I (34 subjects), Achalasia pattern II (44 subjects), Achalasia pattern III (7 subjects), Esophago-Gastric Junction (EGJ) outflow obstruction (39 subjects), hypertensive LES (9 subjects), Nutcracker esophagus (14 subjects) and Diffuse Esophageal Spasm (9 subjects). The identified model parameters were analyzed, and their distributions were assessed for each group of subjects, as basis for the implementation of the autonomic diagnosis procedure. Thus, the condition of a generic patient could be determined through the evaluation of a similarity index designed to correlate the model parameters of the patient to the parameters distributions of the training set.
As a result, a preliminary set of HRMs of healthy and pathological subjects was collected for a proper design and testing of the autonomic diagnosis software. The suitability of the developed physiological model was assessed by evaluating the coefficient of determination R2 between clinical data and model results, ranging from 83% to 96% among the different groups of subjects. The application of the model to each subject of the dataset allowed to assess the distribution of model parameters with regard to different healthy or pathological conditions, as the basis for the development of the autonomic diagnosis procedure. Furthermore, the main differences between the parameters distributions of pathological groups and the parameters distribution of the healthy group were observed in specific regions where the different symptoms are manifested, endorsing the suitability of the model to interpret the variation of physiological properties in pathological situations. Finally, the reliability of the autonomic diagnosis procedure was assessed by analyzing the performance of the algorithm, which was able to match the correct diagnosis in the 86% of the considered cases. Results suggest that the computational tools provided may represent a reliable support to the medical staff during the traditional diagnostic activity.
As model parameters distributions represent the basis for the autonomic diagnosis procedure, there is room for improvement of the algorithm by considering a larger training set, which must be extended and continuously updated involving different research groups, as a future development of the research activity. Furthermore, the autonomic diagnosis procedure should be extended, in order to make it capable to diagnose pathologies accounting for additional clinical tests providing information about conductivity, morphometry and mechanical behavior of the involved biological tissues. Such information should be collected in a single clinical test in order to reduce costs and invasiveness for the patient, and can be performed by means of an innovative esophageal endoscope that is already under development
A review of the effects of some endocrinological factors on respiratory mechanics.
Full text linkContext: Endocrinological factors have been recently described to affect respiratory mechanics.
Objective: To review recent literature data, most of all obtained by the end-inflation occlusion
method, describing the effects of molecules of endocrinological interest such as endothelin,
erythropoietin and renin-angiotensin, on respiratory mechanics parameters.
Methods: The papers considered in this review were found by inserting in Pubmed/Medline the
following indexing terms: hormones, endothelin, erythropoietin, angiotensin and respiratory
mechanics.
Results: It was found that the above cited molecules, beside their well known physiological
main effects, exhibit influences on respiratory mechanics, most of all on the airflow resistance,
which was described to be increased by endothelin and angiotensin, and decreased by
erythropoietin.
Conclusions: A number of molecules of biological interest exhibit unexpected influences on
respiratory mechanics. The clinical effects depend on the consequences of modified inspiratory
pressure values the respiratory muscles have to perform for a given breathing pattern
Analysis of the biomechanical behaviour of gastrointestinal regions adopting an experimental and computational approach
No full textAn integrated experimental and computational procedure is provided for the evaluation of the biomechanical behaviour that characterizes the pressure-volume response of gastrointestinal regions. The experimental activity pertains to inflation tests performed on specific gastrointestinal conduct segments. Different inflation processes are performed according to progressively increasing volumes. Each inflation test is performed by a rapid liquid in-flaw, up to a prescribed volume, which is held constant for about 300 s to allow the development of relaxation processes. The different tests are interspersed by 600 s of rest to allow the recovery of the specimen mechanical condition. A physio-mechanical model is developed to interpret both the elastic behaviour of the sample, as the pressure-volume trend during the rapid liquid in-flaw, and the time-dependent response, as the pressure drop during the relaxation processes. The minimization of discrepancy between experimental data and model results entails the identification of the parameters that characterize the viscoelastic model adopted for the definition of the behaviour of the gastrointestinal regions. The reliability of the procedure is assessed by the characterization of the response of samples from rat small intestine
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A physiological model for the investigation of esophageal motility in healthy and pathologic conditions
No full textRecent technological advances in esophageal manometry allowed the definition of new classification methods for the diagnosis of disorders of esophageal motility and the implementation of innovative computational tools for the autonomic, reliable and unbiased detection of different disorders. Computational models can be developed aiming to interpret the mechanical behavior and functionality of the gastrointestinal tract and to summarize the results from clinical measurements, as high-resolution manometry pressure plots, into model parameters. A physiological model was here developed to interpret data from esophageal high-resolution manometry. Such model accounts for parameters related to specific physiological properties of the biological structures involved in the peristaltic mechanism. The identification of model parameters was performed by minimizing the discrepancy between clinical data from high-resolution manometry and model results. Clinical data were collected from both healthy volunteers (n=35) and patients with different motor disorders, such as achalasia patterns 1 (n=13), 2 (n=20) and 3 (n=5), distal esophageal spasm (n=69), esophago-gastric junction outflow obstruction (n=25), nutcracker esophagus (n=11) and normal motility (n=42). The physiological model that was formulated in this work can properly explain high-resolution manometry data, as confirmed by the evaluation of the coefficient of determination R-2=0.83 - 0.96. The study finally led to identify the statistical distributions of model parameters for each healthy or pathologic conditions considered, addressing the applicability of the achieved results for the implementation of autonomic diagnosis procedures to support the medical staff during the traditional diagnostic process
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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