Articles: respiratory-distress-syndrome.
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Critical care medicine · Nov 1993
Comparative StudyAccurate assessment of right ventricular function in acute respiratory failure.
Since right ventricular ejection fraction is highly dependent on afterload, right ventricular ejection fraction may not reflect right ventricular contractile function in acute respiratory failure. Despite a severe reduction in right ventricular ejection fraction, the right ventricle may be able to generate pressure output that is sufficient enough to maintain an adequate distribution of pulmonary perfusion. We tested this hypothesis by assessing the correlation between the right ventricular ejection fraction and the right ventricular end-systolic pressure-volume relationship, and by assessing the correlations between right ventricular ejection fraction and the physiologic deadspace/tidal volume ratio and between the physiologic deadspace/tidal volume ratio and the right ventricular end-systolic pressure-volume relationship. ⋯ These data suggest that in acute respiratory failure, the right ventricular ejection fraction does not reflect right ventricular performance.
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The justification for restricting fluid administration, or more directly, for actively trying to lower pulmonary capillary pressures during pulmonary edema, is embodied in the familiar "Starling equation." This model predicts that pulmonary edema will develop if lymph flow or changes in other so-called "safety factors" cannot compensate for increases in pulmonary capillary pressures. Numerous experimental studies support the logical extension of this paradigm, namely that reduced capillary pressures and/or reduced perfusion to acutely injured lung units will result in reduced extravascular lung water accumulation. ⋯ Furthermore, although a strategy of fluid restriction/diuresis could potentially increase the risk of either cardiac or renal dysfunction, currently available data suggest that this management strategy in euvolemic (and certainly in hypervolemic) ARDS patients can be pursued without clinically important deterioration in either type of organ function. Thus, on balance, a strategy of fluid restriction/diuresis should be pursued during the first few days of ARDS, while carefully monitoring and supporting the perfusion of vital organs.
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Conventional therapy in the management of adult respiratory distress syndrome is often associated with an increased mortality rate. Several methods to improve survival in patients with severe respiratory insufficiency are under evaluation. One recently developed method of treatment is an implantable intravascular oxygenator, which provides supplemental gas exchange for failing lungs. ⋯ Reduction in ventilator settings such as airway pressure, oxygen concentration, positive end-expiratory pressure and minute volume can be achieved, decreasing the likelihood of oxygen toxicity and barotrauma. Success of the intravascular oxygenator in adult respiratory distress syndrome is dependent in part on critical care staff expertise. Therefore, a thorough understanding of the operation of this device and its role in acute respiratory failure is necessary for optimal care.