ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

The purpose of this review is to highlight areas in alveolar cell biology in which our understanding of the effects of mechanical stress have been advanced in the last year, focusing on intracellular signal transduction pathways, the surfactant system, and cell injury and repair. Mechano-transduction pathways are only now beginning to be elucidated in alveolar cells. The importance of the mitogen-activated protein kinase, G protein, and growth factor systems is emphasized. The research conducted in the last year has also stressed the importance of alveolar cell cross-talk, with surfactant exocytosis being facilitated through parathyroid hormone–related peptide and leptin and calcium in interstitial fibroblasts and endothelial cells, respectively. Finally, the importance of deformation-induced plasma membrane breaks is emphasized. Alveolar cells were found to exocytose intracellular lipid vesicles to the plasma membrane—not only to prevent cell breaks but also to reseal cell breaks. This dynamic process was a stronger determinant of cell breaks than the prestress properties of the cytoskeleton. All of these exciting findings provide further potential treatment targets for ventilator-induced lung injury.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

In this review, we discuss the heat shock response, a specific example of gene expression that has been studied over the past 25 years, and its relevance to acute lung injury and other critical conditions. The heat shock response has been observed in virtually all organisms and involves the rapid induction of a set of highly conserved genes that encode heat shock proteins (HSPs). The HSP70 family represents the most prominent eukaryotic group of HSPs. It has been suggested that members of the HSP70 family act in the protection of cellular damage by binding to denatured or abnormal proteins after heat shock, thereby preventing protein aggregation. The capacity of HSPs to subserve cytoprotection has produced considerable interest from the perspective of elucidating the pathophysiology of organ damage and dysfunction. Several studies support the hypothesis that HSPs are cytoprotectivein vivo.In addition, recent investigations have demonstrated that HSP70 is released into the systemic circulation and is involved in the activation of innate immunity.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Even a slight increase in pulmonary vascular resistance can overload a normal right ventricle, which ejects blood through a low-pressure circuit. In a clinical setting, a persistent increase in pulmonary vascular resistance produces acute cor pulmonale. From an echocardiographic point of view,acute cor pulmonalemay be defined as the combination of a paradoxical septal motion, reflecting systolic overload, with right ventricular enlargement, reflecting diastolic overload. In patients with acute respiratory distress syndrome, this complication reflects the severity of the pulmonary disease involving the microvasculature but may also be caused or exacerbated by an aggressive ventilatory strategy. In the past, conventional respiratory support used in acute respiratory distress syndrome to obtain normocapnia was associated with a poor prognosis and a high frequency of acute cor pulmonale, suggesting some relation between the two findings. This prognosis has greatly improved with protective ventilation. At the same time, the incidence of acute cor pulmonale has diminished in acute respiratory distress syndrome, and the prognosis of this specific complication has also improved, suggesting that the right ventricle may develop some adaptation against persistent overload. Past lessons, however, have taught us that this potential may be limited and lead us to recommend right ventricular protection during mechanical ventilation.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Reduction of tidal volume to limit plateau pressure currently is recommended for the ventilatory management of acute respiratory distress syndrome. However, sufficient evidence now exists to support the fact that excessive reduction in tidal volume may result in harmful alveolar derecruitment depending on the level at which positive end-expiratory pressure is set. The use of recruitment maneuvers has been proposed as an adjunctive lung-protective strategy to reverse low tidal volume–related derecruitment. Many questions remain regarding the basic physiologic principles of recruitment, and, therefore, the optimal way to perform recruitment maneuvers remains unknown. Moreover, apart from physiologic studies suggesting a potential benefit of recruitment maneuver in terms of recruitment and gas exchange, no data are yet available that demonstrate the ability of such a maneuver to improve outcome. In this article, we discuss the physiologic rules governing recruitment and derecruitment and review articles that provide new insights in the field of recruitment maneuver.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

The last decade has seen increased appreciation of ventilator-induced lung injury. The understanding that the process of mechanical ventilation can itself damage lungs has spurned the search for ventilation strategies that are more lung protective. High-frequency oscillatory ventilation is a mode of high-frequency ventilation that may accomplish all of the current goals of lung protection. Historically, much of the data evaluating high-frequency oscillatory ventilation came from neonatal and pediatric populations. In the past year, a number of provocative and exciting studies have been published that contribute significantly to our understanding of high-frequency oscillatory ventilation, its role in preventing and reducing ventilator-induced lung injury, and its use in the support of adult patients with lung injury. In this article, we discuss the current understanding of high-frequency oscillatory ventilation and highlight the most recent literature addressing its application in adult patients with acute respiratory distress syndrome.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Mechanical ventilation is a supportive lifesaving therapy that can potentially cause lung injury if periodic alveolar overdistension, or cyclic collapse, and reopening occur. The use of a low tidal volume with moderate to high positive end-expiratory pressure improves the survival of patients with acute lung injury and acute respiratory distress syndrome. Positioning the patient with the “good lung down” and using differential ventilation with selective positive end-expiratory pressure are the two currently accepted ventilatory strategies to be applied in patients with severe unilateral lung injury. However, both have serious limitations in clinical practice. Lung injury may be rather inhomogeneous—confined to one lung or preferentially distributed toward the dependent lung areas. In unilateral lung injury, ventilatory strategies that allow recruitment of injured lung and that avoid overdistension of uninjured lung parenchyma should be applied. Experimental studies have shown that the use of selective tracheal gas insufflation and partial liquid ventilation facilitates low tidal volume with appropriate gas exchange while reducing cyclic lung stretch and shear stresses. Further studies are needed to determine future applications of these therapies in humans.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

The effect of the settings of inspiratory time and inspiratory flow during assist–control ventilation on the response of a patient's respiratory controller has been the subject of intense research during the last few years. An increase in inspiratory flow or a decrease in tidal volume delivered by the ventilator is associated with prompt increases in respiratory frequency. The changes occur before any change in arterial blood gases can take place. These responses occur both during wakefulness and sleep and in health and disease states. Whether the responses are the result of Hering-Breuer reflex activity or they arise in flow-sensitive receptors remains to be defined. Important clinical implications of the respiratory rate response to changes in ventilatory settings include effects on carbon dioxide, intrinsic positive end-expiratory pressure, and, possibly, on the instability of the respiratory rate in the transition between wakefulness and sleep.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

The density of helium is markedly lower than that of air or any of its components, leading to a substantial decrease in airway resistance to flow when it is inhaled. In mechanically ventilated patients with obstructive airway disease, replacing the usual air–oxygen mixture with helium–oxygen has been shown to reduce dynamic hyperinflation and intrinsic positive end-expiratory pressure; to decrease lung inflation pressures, respiratory acidosis, and work of breathing; and to improve arterial blood gases. Aerosol delivery to distal airways is enhanced with helium–oxygen. Preliminary data also suggest that the use of helium–oxygen could be a valuable approach to decrease postextubation respiratory distress. However, interference with ventilator function and added costs are two major disadvantages of helium–oxygen. Hence, before its widespread use in mechanically ventilated patients can be recommended, studies are needed to determine whether these favorable short-term effects can influence patient outcome.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Increased knowledge of the mechanisms that determine respiratory failure has led to the development of new technologies aimed at improving ventilatory treatment. Proportional assist ventilation and neurally adjusted ventilatory assist have been designed with the goal of improving patient–ventilator interaction by matching the ventilator support with the neural output of the respiratory centers. With proportional assist ventilation, the support is continuously readjusted in proportion to the predicted inspiratory effort. Neurally adjusted ventilatory assist is an experimental mode in which the assistance is delivered in proportion to the electrical activity of the diaphragm, assessed by means of an esophageal electrode. Biologically variable (or fractal) ventilation is a new, volume-targeted, controlled ventilation mode aimed at improving oxygenation; it incorporates the breath-to-breath variability that characterizes a natural breathing pattern.

ISSN:1070-5295    

出版商:OVID    

年代:2003

数据来源: OVID