Chapters authored
Severe Acute Respiratory Distress Syndrome
Acute respiratory distress syndrome is characterized by an increase of the permeability of the lungs’ alveolar-capillary membranes, leading to the extravasation of liquid rich in proteins inside the alveolar spaces that turns air-filled lungs into heavy high-osmotic pressure liquid-filled lungs. The consequence is the collapse of the lowermost lung regions, shunt, refractory hypoxemia, decrease in lungs’ compliance and increase in dead spaces that are more pronounced with the severity of the permeability changes of the pulmonary alveoli-capillary membrane. According to the recent Berlin definition, severe acute respiratory distress syndrome is defined by bilateral pulmonary infiltrates of recent onset (less than 1 week) in a patient with a risk factor for ARDS that has a PaO2/FIO2 equal or less than 100 with a positive end-expiratory pressure equal or more than 5 cm H2O with no evidence of cardiac failure or hypervolemia. Severe ARDS patients present a higher mortality ratio, a more difficult mechanical ventilatory support (higher airway pressures with low tidal ventilation and higher PaCO2 levels) and benefits for adjunctive ventilatory support therapy. The recommended mechanical ventilatory support in severe ARDS is with low tidal ventilation (less than 6 mL/Kg predicted body weight) with driving inspiratory pressures less than 15 cm H2O, respiratory rate sufficient to keep adequate minute ventilation and PaCO2 levels. PEEP higher than 15 cm H2O and prolonged prone position are recommended for more severe patients to improve their survival. Adjunctive recruitment maneuvers can be used to improve oxygenation and allow more homogeneous ventilation and PEEP titration. In refractory hypoxemia and especially in younger patients with prognosis, extra-corporeal veno-venous membrane oxygenation support can be used.
Part of the book: Advances in Extra-corporeal Perfusion Therapies