The standard of my test is as follows: <70 years, PaO2/FiO2> 250, ELWI ≤ 10, PaO2> 100 mmHg, FiO2 <50%, MAP> 22 60 mmHg, heart rate 60 - 80 times / min, sinus rhythm, CI> 3 liter / min / m2, CVP<12 mmHg, dobutamine / dopamine ≤ 5 µg / kg / min, adrenaline / noradrenaline <0.05 µg / kg / min, clear 2-sided X-ray, smokes<20 packs / year, no chest injury, no reflux or infection, no history of cardiopulmonary surgery, no bacteria on the gram stain, no secretions / gastric juice during bronchoscopy, no history of chronic lung disease.