The aim of the study: The application of progressive change position program in lung health in patients undergoing mechanical ventilation. Design of study: Progressive change position program is gradually putting the patient in the chair position that 3 times a day and in three different shifts, for 4 days, will be done and Includes the following steps: The head of the bed at an 45 degrees and the foot of the bed an -75 degrees for 15 minutes; The head of the bed at an 60 degrees and the foot of the bed an -75 degrees for 15 minutes; The head of the bed at an 75 degrees and the foot of the bed an -75 degrees for 30 minutes. In this study, drug or chemical composition will not be used. In this study of the ergonomics rule is used to determine the angles of the bed. Healthy lungs in this study is the respiratory index in the range of natural and not infection to mechanical ventilation pneumonia. Sampling method: Completely randomized block design Study population: All newly admitted patients under mechanical ventilation tube in the ICU. Inclusion criteria: Age between 18 to 65 years; Having oral endotracheal tube; Connected to a mechanical ventilator; Lack of previous pneumonia by chest radiography; Lack of Immunosuppressive diseases; Lack of Immunosuppressive drug; Lack of damage to the spine and being permitted to impose conditions according to intensive care specialist. Exclusion criteria: The patient died during the study; Leaving the endotracheal tube at the time of the study; The separation of mechanical ventilation during the study; The risk of pneumonia after 24 hours according to intensive care specialist. Sample: 30 patients in each group Method: First newly admitted patients under mechanical ventilation tube in the ICU are evaluated for inclusion criteria and the patients with inclusion criteria are selected and investigated for mechanical ventilation pneumonia by intensive care specialist. The patients with pneumonia are removed and then the sampling, the samples in the intervention group or control will be done. Then in the intervention group, 24 hours after admission, the progressive change position program until obtain exclusion criteria by the researcher and trained nurses will be done. Progressive change position program are as follows: The head of the bed at an 45 degrees and the foot of the bed an -75 degrees for 15 minutes The head of the bed at an 60 degrees and the foot of the bed an -75 degrees for 15 minutes The head of the bed at an 75 degrees and the foot of the bed an -75 degrees for 30 minutes In both groups, routine care will be alike. Respiratory parameters in intervention group (Respiratory rate, Tidal volume, Minute ventilation and Arterial oxygen saturation) before the program, half an hour after starting the program, immediately after and one hour after the end of the program will be measured and recorded. Respiratory parameters in control group (Respiratory rate, Tidal volume, Minute ventilation and Arterial oxygen saturation) at the same intervals as the intervention group will be recorded. 48 and 96 hours after study (Two times during the study) patients will be examined by colleague physician based on set criteria from pneumonia associated with mechanical ventilation, and cases of pneumonia associated with mechanical ventilation will be recorded.