Current opinion in critical care
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Curr Opin Crit Care · Feb 2002
ReviewPulmonary versus extrapulmonary acute respiratory distress syndrome: different diseases or just a useful concept?
The acute respiratory distress syndrome may complicate both pulmonary and extrapulmonary conditions. There is a growing belief that the predisposition to, and clinical course of, the syndrome may be influenced by the extent to which the lung is directly involved in the precipitating pathologic changes. Several studies have highlighted differences in morphology and respiratory physiology between the two subgroups in the early stages of acute respiratory distress syndrome. ⋯ There are, however, inconsistencies between various studies addressing these issues, which may relate in part to differences in etiologic case mix. There are also practical difficulties in assigning certain cases to one of these two groups. Finally, there are as yet no outcome data to support any modification of clinical management on the basis of this distinction.
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Increased knowledge of the pathophysiologic mechanisms of impaired gas exchange during acute respiratory failure during recent years has stimulated many studies that evaluate different treatments to improve oxygenation and outcome. Changes in body position (mainly prone positioning) can significantly improve gas exchange in patients with acute respiratory distress syndrome and acute lung failure, with few complications related to the maneuver; however, no survival advantage has yet been detected. A correlation between aerated lung tissue and oxygenation also confirms the importance of recruitment maneuvers in improving gas exchange. ⋯ New data support the hypothesis that maintenance of even small amount of spontaneous breathing during mechanical ventilation (with airway pressure release ventilation or biphasic positive airway pressure) can improve gas exchange, whereas other unconventional ventilatory modes have not yet proved advantageous. Some mechanisms responsible for the high percentage of nonresponse to inhaled nitric oxide have recently been proposed, and combinations of inhaled nitric oxide with other therapies have been tested. Increased knowledge in this area may, in the future, make inhaled nitric oxide more attractive in the treatment of adult respiratory failure as well as in neonatal intensive care.
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Curr Opin Crit Care · Feb 2002
ReviewReinterpreting the pressure-volume curve in patients with acute respiratory distress syndrome.
New evidence requires a reinterpretation of the inflation pressure-volume curve and suggests that neither the lower nor the upper inflection point provides reliable information to determine safe ventilator settings in the acute respiratory distress syndrome. Recruitment probably continues throughout the inflation pressure-volume curve, and studies of the deflation pressure-volume curve, reinflations after partial deflation, or decremental positive end-expiratory pressure trials after a recruitment maneuver are probably needed to determine open-lung positive end-expiratory pressure.
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Curr Opin Crit Care · Feb 2002
ReviewGenetics and the pathogenesis of adult respiratory distress syndrome.
Most human diseases are substantially affected by genetic factors. It now seems clear that the pathogenesis of most diseases lies in complex interactions among the genotype, the environment, and the nature of the process that leads to cell, tissue, organ, or systemic injury. The information derived from the knowledge of the recent completion of the human genome, when combined with the sophisticated tools of molecular biology, will provide the framework for more rapid identification of the genes responsible for susceptibility to disease. ⋯ Markers of susceptibility will indicate differences in individuals or populations that affect the body's response. The underlying principle of susceptibility markers is the interindividual differences that confer sensitivity or resistance to environmentally induced diseases. This article reviews some of those susceptibility factors for critical illness and acute lung injury.
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Curr Opin Crit Care · Feb 2002
ReviewRole of reactive oxygen and nitrogen species in acute respiratory distress syndrome.
Reactive oxygen species are reactive, partially reduced derivatives of molecular oxygen (O 2 ). Important reactive oxygen species in biologic systems include superoxide radical anion, hydrogen peroxide, and hydroxyl radical. Closely related species include the hypohalous acids, particularly hypochlorous acid; chloramine and substituted chloramines; and singlet oxygen. ⋯ This view is further supported by data from clinical studies that correlate biochemical evidence of reactive oxygen species-mediated or reactive nitrogen species-mediated stress with the development of acute respiratory distress syndrome. Despite these data, pharmacologic strategies directed at minimizing reactive oxygen species-mediated or reactive nitrogen species-mediated damage have yet to be successfully introduced into clinical practice. The most extensively studied compound in this regard is N -acetylcysteine; unfortunately, clinical trials with this compound in patients with acute respiratory distress syndrome have yielded disappointing results.