[Mechanical ventilation in acute respiratory distress syndrome (ARDS): lung protecting strategies for improved alveolar recruitment].

For patients with acute respiratory distress syndrome (ARDS) the most important objective of mechanical ventilation is opening and keeping open the alveoli to achieve adequate oxygenation, without further damaging the lungs or negatively affecting the circulation. Alveolar recruitment is achieved by making use of positive end-expiratory pressure (PEEP). The best PEEP level is that with which the largest improvement in oxygen transport and lung compliance is achieved, without a decrease in the stroke volume of the left ventricle. In addition to the usual volume-controlled ventilation with PEEP, pressure-limited ventilation is also possible. In this a preselected pressure is never exceeded, whereas a maximum inspiratory airflow at the start of inspiration provides more opportunity for gaseous exchange. The oxygenation can possibly be further improved by increasing the inspiration-expiration ratio. As a result of the reduced expiratory period the alveoli which tend to collapse at the end of a normal expiration are kept open. Mechanical ventilation with a lower tidal volume decreases mortality. Ventilation in a prone position increases the end-expiratory lung volume and reduces the intrapulmonary shunt and the regional differences in the degree of ventilation. These factors possibly contribute to preventing ventilation-induced lung damage. Administration of natural surfactant during the ventilation of patients with ARDS seems to be a highly promising strategy; the clinical effectiveness still needs to be demonstrated.