Seminars in respiratory and critical care medicine
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Early reports of late outcomes among survivors of ARDS indicated that most patients improved dramatically after their intensive care unit stay, and few lived with residua of their once-severe pulmonary injury. Over the last decade, a collection of new studies with improved methodology and novel questions has improved our understanding of life after ARDS. After reviewing these newer investigations in the context of previously published literature, we have drawn several preliminary conclusions: (1) Long-term survival after hospital discharge is unaffected by ARDS, but is strongly affected by ARDS risk factor and comorbidities. (2) Respiratory symptoms after ARDS are more prevalent than previously indicated, but improve over the first 12 months of recovery. (3) Pulmonary function testing reveals marked impairment soon after ARDS. ⋯ A small group of patients have severe impairment without improvement. (4) Quality of life, functional independence, and cognitive function are severely affected by ARDS, with dramatic improvement over the first year. Quality of life is lower than in matched critically ill controls. (5) Significant numbers of ARDS survivors suffer from posttraumatic stress syndrome. This is an exciting time for research in long-term outcomes of ARDS, with potential for future studies that validate these single-center hypotheses, explore their ramifications, and investigate the impacts of changing practices in the intensive care unit in the acute phase of ARDS.
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The acute respiratory distress syndrome (ARDS) is a life-threatening syndrome that may occur in any patient without any predisposition and that is mostly triggered by underlying processes such as sepsis, pneumonia, trauma, multiple transfusions, and pancreatitis. ARDS is defined by (1) acute onset, (2) bilateral infiltrates in chest x-rays, (3) absence of left ventricular failure, and (4) severe arterial hypoxemia with a PaO2/FiO2 ratio less than 200 mmHg. Still, ARDS is feared (mortality 30-40%) and relatively frequent (incidence between 13.5 per 100,000 to 75 per 100,000). ⋯ Despite ongoing and intensive scientific research in this area, the mechanisms underlying ALI/ARDS are still not completely understood, and until recently, there were no studies demonstrating any beneficial effect of a single treatment modality in ARDS. The recent report that a specific approach to ventilatory support can significantly reduce mortality in ARDS underscores the need for better understanding of the pathophysiological events occurring in this syndrome. This review therefore summarizes the current pathophysiological concepts underlying the evolution of acute hypoxemic respiratory failure and focuses on: (1) possible reasons for the development of ALI/ARDS; (2) cellular and humoral mediator responses leading to a sustained and self-perpetuating inflammation of the lung; (3) consequences with regard to fluid balance, pulmonary perfusion, ventilation, and efficiency of gas exchange; and (4) mechanisms underlying the aggravating complications commonly seen in ARDS, especially ventilator-associated lung injury, ventilator-associated pneumonia, and lung fibrosis.
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Semin Respir Crit Care Med · Jun 2001
Ventilator-associated pneumonia complicating the acute respiratory distress syndrome.
Pulmonary infections span a wide spectrum, ranging from self-limited processes (e.g., tracheobronchitis) to life-threatening infections including both community-acquired pneumonia (CAP) and hospital-acquired pneumonia (HAP). Together, pneumonia and influenza rank as the sixth leading cause of death in the United States and lead all other infectious diseases in this respect. Pneumonia is the second-most-common hospital-acquired infection in the United States, accounting for 17.8% of all hospital-acquired infections and 40,000 to 70,000 deaths per year. ⋯ The greater hospital mortality associated with these "high-risk'' pathogens has been attributed to the virulence of these bacteria and the increased occurrence of inadequate initial antibiotic treatment of VAP due to the presence of antibiotic resistance. This review provides an overview of the clinical importance of VAP. We then describe how this nosocomial infection influences the management and outcomes of patients with the acute respiratory distress syndrome (ARDS).
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Semin Respir Crit Care Med · Jun 2001
Pulmonary and extrapulmonary forms of acute respiratory distress syndrome.
Acute respiratory distress syndrome (ARDS) is usually viewed as the functional and morphological expression of a similar underlying lung injury caused by a variety of insults. However, the distinction between ARDS due to a direct (ARDSp) versus an indirect (ARDSexp) lung injury is gaining more attention as a means of better comprehending the pathophysiology of ARDS and for modifying ventilatory management. ⋯ It is possible that the two insults may coexist (i.e., one lung with direct injury (as in pneumonia) and the other with indirect injury, through mediator release from the contralateral pneumonia); (2) the radiological pattern, by chest x-ray or computed tomography (CT), is different in ARDSp (characterized by prominent consolidation) and ARDSexp (characterized by prominent ground-glass opacification); (3) in ARDSp lung elastance is more markedly increased than in ARDSexp, where the main abnormality is the increase in chest wall elastance, due to abnormally high intra-abdominal pressure; (4) positive end-expiratory pressure (PEEP), inspiratory recruitment, and prone position are more effective to improve respiratory mechanics, alveolar recruitment, and gas-exchange in ARDSexp. Further studies are warranted to better define if the distinction between ARDS of different origins can improve clinical management and survival.