First, during controlled mechanical ventilation all patients will be ventilated for 5 minutes with 100% oxygen. After 5 minutes an PaO2/FiO2 will be calculated and compared with a PaO2/FiO2 during ventilation with FiO2 - 30%.~The patients will be divided in two sections: Section A are the patients with less than 24 hours mechanical ventilation until weaning start. Section B are the patients with more than 24 hours until weaning start.~The patients in every section will be further divided in two groups. Group 1 will be weaned starting with a PEEP equal with P mean during BiPAP, Group 2 will be weaned starting with a PEEP equal with PEEP during BiPAP.~Further, the weaning will be conducted after an known algorithm. The differences in the oxygenation and decarboxylation will be measured after 30 and 120 Minutes for Group A and after 30, 120, 240, 360 Minutes for Group B.
The purpose of this study is to determine the differences in oxygenation and decarboxylation between two weaning processes.