[Current modalities of mechanical ventilation for acute respiratory failure in chronic respiratory insufficiency]

Acute respiratory failure in patients with chronic obstructive lung disease is a frequent and serious complication, with a mortality rate of 20 p. 100 and 57 p. 100 of the patients kept under mechanical ventilation for more than two weeks. The main problem with mechanical ventilation is an unavoidable intrinsic positive expiratory pressure and a hyperinflation that can be increased by the different modes of ventilation. All the classical modes of mechanical ventilation may be used, including control-mode ventilation, assist/control-mode ventilation, intermittent mandatory ventilation and ventilation with inspiratory assistance. Another major problem is weaning from mechanical ventilation as it may take a long time or even be impossible, so that the patients stay in intensive care units for ages or require long-term home ventilation. At the moment, there is no way of predicting the outcome of weaning in each individual subjects, and none of the various ventilation procedures has proved superior to the others. Nasal ventilation has recently been introduced in intensive care where it constitutes a major step forward being less invasive; it avoids intubation in 60 p. 100 of the patients but is more exacting for the physicians and nursing staff; finally, it makes it possible to treat acute respiratory failure at an earlier stage than previously.