1,721,012 research outputs found
Assessing peak inspiratory flow for initial HFNC flow setting: the end point or a first step towards a new approach?
No full textWe read with interest the report by Milesi et al1 showing a new physiologic approach for setting high flow nasal cannula (HFNC) therapy in infants with bronchiolitis, based on actual inspiratory flow demands, by measuring peak tidal inspiratory flow (PTIF) before HFNC therapy begins. In this study, 29% of PTIF values were >2 L/kg/min. The Authors thus cautiously propose a higher initial HFNC flow rate of 2.5 L/kg/min (or >3 L/kg/min in particular cases) than the commonly used 2 L/kg/min.
We acknowledge the authors’ effort to identify a physiologic variable that may help to couple HFNC flow delivery and patients’ flow demands, the basic principle for HFNC efficacy. However, the study did not evaluate whether HFNC therapy itself influences patients’ PTIF and thus if the set HFNC flow becomes inadequate or exceedingly high after HFNC begins. We wish to raise some concerns that we see as crucial for their subsequent clinical implications. Although their findings question whether 2 L/kg/min is adequate in young infants with bronchiolitis, previously published clinical and physiologic studies suggest that this setting may be the correct choice in most infants. Previous clinical findings show that flow rates higher than 2 L/kg/min (i.e., 3 L/kg/min) bring about no further improvement.2 Weiler et al found a dose-dependent relationship between increasing HFNC flow rates and the reduced effort of breathing, optimal flow rates ranging between 1.5 and 2.0 L/kg/min .3 Thus, we wonder whether evaluating PTIF only once before HFNC therapy, and then using this PTIF value to set HFNC without further verification, is the right way to match patients and HFNC flow. An empirically consistent scenario is that PTIF will change once HFNC therapy begins. Indeed, breathing frequency slows during HFNC, and longer times flatten the flow tracings, thus reducing PTIF. Equally important, because HFNC therapy reduces esophageal pressure swings, PTIF values will likely diminish. Thus, after HFNC starts, reduced PTIF values might meet a 2 L/kg/min set flow rate or an even lower threshold.
Although HFNC was developed as a procedure with no monitoring requirement, today’s expanded use requires extended physiologic studies to guide clinicians in setting HFNC flow. This study has uncovered the important issue of measuring PTIF to set the optimal initial HFNC flow rate and for that the authors should be complimented; however, we believe that further work is needed to verify what happens to PTIF during HFNC therapy
A flow-leak correction algorithm for pneumotachographic work-of-breathing measurement during high-flow nasal cannula oxygen therapy
No full textMeasuring work of breathing (WOB) is an intricate task during high-flow nasal cannula (HFNC) ther-
apy because the continuous unidirectional flow toward the patient makes pneumotachography technically
difficult to use. We implemented a new method for measuring WOB based on a differential pneumota-
chography (DP) system, equipped with one pneumotachograph inserted in the HFNC circuit and another
connected to a monitoring facemask, combined with a leak correction algorithm (LCA) that corrects flow
measurement errors arising from leakage around the monitoring facemask. To test this system, we used
a mechanical lung model that provided data to compare LCA-corrected respiratory flow, volume and time
values with effective values obtained with a third pneumotachograph used instead of the LCA to measure
mask flow leaks directly. Effective and corrected volume and time data showed high agreement (Bland–
Altman plots) even at the highest leak. Studies on two healthy adult volunteers confirmed that corrected
respiratory flow combined with esophageal pressure measurements can accurately determine WOB (rel-
ative error < 1%). We conclude that during HFNC therapy, a DP system combined with a facemask and an
algorithm that corrects errors due to flow leakages allows pneumotachography to measure reliably the
respiratory flow and volume data needed for calculating WOB
Expiratory braking defines the breathing patterns of asphyxiated neonates during therapeutic hypothermia
Full text linkIntroduction Although neonatal breathing patterns vary after perinatal asphyxia, whether they change during therapeutic hypothermia (TH) remains unclear. We characterized breathing patterns in infants during TH for hypoxic-ischemic encephalopathy (HIE) and normothermia after rewarming. Methods In seventeen spontaneously breathing infants receiving TH for HIE and in three who did not receive TH, we analyzed respiratory flow and esophageal pressure tracings for respiratory timing variables, pulmonary mechanics and respiratory effort. Breaths were classified as braked (inspiratory:expiratory ratio >= 1.5) and unbraked (<1.5). Results According to the expiratory flow shape braked breaths were chategorized into early peak expiratory flow, late peak expiratory flow, slow flow, and post-inspiratory hold flow (PiHF). The most braked breaths had lower rates, larger tidal volume but lower minute ventilation, inspiratory airway resistance and respiratory effort, except for the PiHF, which had higher resistance and respiratory effort. The braked pattern predominated during TH, but not during normothermia or in the uncooled infants. Conclusions We speculate that during TH for HIE low respiratory rates favor neonatal braked breathing to preserve lung volume. Given the generally low respiratory effort, it seems reasonable to leave spontaneous breathing unassisted. However, if the PiHF pattern predominates, ventilatory support may be required
Synchronized Nasal Intermittent Positive Pressure Ventilation of the Newborn: Technical Issues and Clinical Results
No full textAlthough mechanical ventilation via an endotracheal tube has undoubtedly led to improvement in neonatal survival in the last 40 years, the prolonged use of this technique may predispose the infant to development of many possible complications including bronchopulmonary dysplasia. Avoiding mechanical ventilation is thought to be a critical goal, and different modes of noninvasive respiratory support beyond nasal continuous positive airway pressure, such as nasal intermittent positive pressure ventilation and synchronized nasal intermittent positive pressure ventilation, are also available and may reduce intubation rate. Several trials have demonstrated that the newer modes of noninvasive ventilation are more effective than nasal continuous positive airway pressure in reducing extubation failure and may also be more helpful as modes of primary support to treat respiratory distress syndrome after surfactant and for treatment of apnea of prematurity. With synchronized noninvasive ventilation, these benefits are more consistent, and different modes of synchronization have been reported. Although flow-triggering is the most common mode of synchronization, this technique is not reliable for noninvasive ventilation in neonates because it is affected by variable leaks at the mouth and nose. This review discusses the mechanisms of action, benefits and limitations of noninvasive ventilation, describes the different modes of synchronization and analyzes the technical characteristics, properties and clinical results of a flow-sensor expressly developed for synchronized noninvasive ventilation
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
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
- …
