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Compressive Forces and Computed Tomography-derived Positive End-expiratory Pressure in Acute Respiratory Distress Syndrome
No full textBackground: It has been suggested that higher positive end-expiratory pressure (PEEP) should be used only in patients with higher lung recruitability. In this study, the authors investigated the relationship between the recruitability and the PEEP necessary to counteract the compressive forces leading to lung collapse. Methods: Fifty-one patients with acute respiratory distress syndrome (7 mild, 33 moderate, and 11 severe) were enrolled. Patients underwent whole-lung computed tomography (CT) scan at 5 and 45 cm H2O. Recruitability was measured as the amount of nonaerated tissue regaining inflation from 5 to 45 cm H2O. The compressive forces (superimposed pressure) were computed as the density times the sternum-vertebral height of the lung. CT-derived PEEP was computed as the sum of the transpulmonary pressure needed to overcome the maximal superimposed pressure and the pleural pressure needed to lift up the chest wall. Results: Maximal superimposed pressure ranged from 6 to 18 cm H2O, whereas CT-derived PEEP ranged from 7 to 28 cm H2O. Median recruitability was 15% of lung parenchyma (interquartile range, 7 to 21%). Maximal superimposed pressure was weakly related with lung recruitability (r(2) = 0.11, P = 0.02), whereas CT-derived PEEP was unrelated with lung recruitability (r(2) = 0.0003, P = 0.91). The maximal superimposed pressure was 12 +/- 3, 12 +/- 2, and 13 +/- 1 cm H2O in mild, moderate, and severe acute respiratory distress syndrome, respectively, (P = 0.0533) with a corresponding CT-derived PEEP of 16 +/- 5, 16 +/- 5, and 18 +/- 5 cm H2O (P = 0.48). Conclusions: Lung recruitability and CT scan-derived PEEP are unrelated. To overcome the compressive forces and to lift up the thoracic cage, a similar PEEP level is required in higher and lower recruiters (16.8 +/- 4 vs. 16.6 +/- 5.6, P = 1)
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
Effect of body mass index in acute respiratory distress syndrome
No full textBackground: Obesity is associated in healthy subjects with a great reduction in functional residual capacity and with a stiffening of lung and chest wall elastance, which promote alveolar collapse and hypoxaemia. Likewise, obese patients with acute respiratory distress syndrome (ARDS) could present greater derangements of respiratory mechanics than patients of normal weight. Methods: One hundred and one ARDS patients were enrolled. Partitioned respiratory mechanics and gas exchange were measured at 5 and 15 cm H2O of PEEP with a tidal volume of 6-8ml kg(-1) of predicted body weight. At 5 and 45 cm H2O of PEEP, two lung computed tomography scans were performed. Results: Patients were divided as follows according to BMI: normal weight (BMI 30 kgm(-2)). Obese, overweight, and normal-weight groups presented a similar lung elastance (median [interquartile range], respectively: 17.7 [14.2-24.8], 20.9 [16.1-30.2], and 20.5 [15.2-23.6] cm H2O litre(-1) at 5 cm H2O of PEEP and 19.3 [15.5-26.3], 21.1 [17.4-29.2], and 17.1 [13.4-20.4] cm H2O litre(-1) at 15 cm H2O of PEEP) and chest elastance (respectively: 4.9 [3.18.8], 5.9 [3.8-8.7], and 7.8 [3.9-9.8] cm H2O litre(-1) at 5 cm H2O of PEEP and 6.5 [4.5-9.6], 6.6 [4.2-9.2], and 4.9 [2.4-7.6] cm H2O litre(-1) at 15 cm H2O of PEEP). Lung recruitability was not affected by the body weight (15.6 [6.3-23.4], 15.7 [9.8-22.2], and 11.3 [6.2-15.6]% for normal-weight, overweight, and obese groups, respectively). Lung gas volume was significantly lower whereas total superimposed pressure was significantly higher in the obese compared with the normal-weight group (1148 [680-1815] vs 827 [686-1213] ml and 17.4 [15.8-19.3] vs 19.3 [18.6-21.7] cm H2O, respectively). Conclusions: Obese ARDS patients do not present higher chest wall elastance and lung recruitability
Compressive Forces and Computed Tomography-derived Positive End-expiratory Pressure in Acute Respiratory Distress Syndrome
No full textBackground: It has been suggested that higher positive end-expiratory pressure (PEEP) should be used only in patients with higher lung recruitability. In this study, the authors investigated the relationship between the recruitability and the PEEP necessary to counteract the compressive forces leading to lung collapse. Methods: Fifty-one patients with acute respiratory distress syndrome (7 mild, 33 moderate, and 11 severe) were enrolled. Patients underwent whole-lung computed tomography (CT) scan at 5 and 45 cm H2O. Recruitability was measured as the amount of nonaerated tissue regaining inflation from 5 to 45 cm H2O. The compressive forces (superimposed pressure) were computed as the density times the sternum-vertebral height of the lung. CT-derived PEEP was computed as the sum of the transpulmonary pressure needed to overcome the maximal superimposed pressure and the pleural pressure needed to lift up the chest wall. Results: Maximal superimposed pressure ranged from 6 to 18 cm H2O, whereas CT-derived PEEP ranged from 7 to 28 cm H2O. Median recruitability was 15% of lung parenchyma (interquartile range, 7 to 21%). Maximal superimposed pressure was weakly related with lung recruitability (r(2) = 0.11, P = 0.02), whereas CT-derived PEEP was unrelated with lung recruitability (r(2) = 0.0003, P = 0.91). The maximal superimposed pressure was 12 +/- 3, 12 +/- 2, and 13 +/- 1 cm H2O in mild, moderate, and severe acute respiratory distress syndrome, respectively, (P = 0.0533) with a corresponding CT-derived PEEP of 16 +/- 5, 16 +/- 5, and 18 +/- 5 cm H2O (P = 0.48). Conclusions: Lung recruitability and CT scan-derived PEEP are unrelated. To overcome the compressive forces and to lift up the thoracic cage, a similar PEEP level is required in higher and lower recruiters (16.8 +/- 4 vs. 16.6 +/- 5.6, P = 1)
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
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