Respiration; international review of thoracic diseases
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Mechanical ventilation with a high tidal volume (VT) increases lung and systemic plasminogen activator inhibitor (PAI)-1 levels and alveolar fibrin deposition. Activated protein C (APC) may decrease PAI activity in endothelial cell-conditioned medium and thus enhance fibrinolysis. ⋯ These results suggest that APC administered at a higher dosage might improve lung function by reducing alveolar protein leakage and systemic coagulation.
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Resident tissue macrophages exert important functions during severe systemic infection and contribute to changes in local as well as systemic immune responses. Alveolar macrophages (AM) play a crucial role in airway diseases and in the defense against microorganisms invading the body via the bronchopulmonary tract. It has been postulated that AM are involved in the development of acute local disorders as a consequence of extrapulmonary stimuli like pancreatitis, peritonitis, or trauma. ⋯ Contrarily to other macrophage populations, AM do not significantly contribute to local and systemic cytokine release during polymicrobial abdominal sepsis. AM have important protective functions for local clearance of gut-derived bacteria and attenuation of lung injury.
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Clinically, the symptoms and limited exercise capabilities of patients with chronic obstructive pulmonary disease (COPD) correlate better with changes in lung volumes than with airflow measurements. The realization of the clinical importance of hyperinflation has been overshadowed for decades by the use of forced expiratory volume during 1 s (FEV(1)) and the ratio of the FEV(1) to the forced expiratory vital capacity (FEV(1)/FVC) to categorize the severity and progression of COPD. Hyperinflation is defined as an elevation in the end-expiratory lung volume or functional residual capacity. ⋯ Severe hyperinflation is the major physiologic cause of the resulting hypercarbic respiratory failure and patients' inability to transition (i.e. wean) from mechanical ventilatory support to spontaneous breathing. This paper reviews the basic physiologic principles of hyperinflation and its clinical manifestations as demonstrated by PEEPi. Also reviewed are the adverse effects of hyperinflation and PEEPi in critically ill patients with COPD, and methods for minimizing or counterbalancing these effects.
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Randomized Controlled Trial Comparative Study
Metabolic and respiratory variables during pressure support versus synchronized intermittent mandatory ventilation.
Mechanically ventilated patients interact and respond differently to different modes of ventilatory support. ⋯ Changes in the level of PSV resulted in smaller changes in metabolic and respiratory variables compared with equivalent changes in the level of volume-cycled SIMV support. PSV may be more suitable for progressive respiratory muscle reloading.