MODERN MODES OF VENTILATION

Mechanical ventilation has become a widely used technique in anaesthes iology and intensive care medicine. Difficulties arise with patients w ho suffer from acute or chronic pulmonary disease. Lung models are use d to simulate the behaviour of healthy and diseased lungs and to optim ize breathing patterns. Flow-controlled ventilation is suitable for he althy lungs. Diseased lungs need more finely differentiated ventilator y modes that adapt to the different time constants within the lung. PC V seems to have some advantages in ventilation of such lungs. It has b een demonstrated that prolongation of inspiratory time and inversion o f the I:E ratio can open nonventilated compartments of the lung and th us reduce intrapulmonary shunt. BiPAP ventilation and APRV serve the s ame purpose. Additionally, they support spontaneous breathing of the p atient. Weaning from the respirator can be achieved by either reducing the number of mandatary breaths (IMV, SIMV, MMV) or reducing the work of breathing by applying inspiratory pressure support (PSV). Both tec hniques can be applied simultaneously. BiPAP ventilation and APRV are also suitable for weaning patients from a ventilator. Respirators able to adapt breathing patterns to the lung mechanics of a patient automa tically on the basis of a breath-to-breath lung function analysis (ALV ) are currently in clinical development.