Goal of this study is to determine optimal PEEP levels for patients undergoing surgery in lateral decubitus position. Patients will be randomized into 3 groups - PEEP 0, 5 and 10 mbar. Endotracheal anesthesia will be conducted with propofol, fentanyl, rocuronium and sevoflurane/O2/air gas mixture.

Patients with preexisting lung disease, organ transplants and disseminated malignant disease will be excluded.

Demographic data - age, weight, height, ASA status, smoking history will be recorded. EIT measured parameters - tidal variation ratio of nondependent and dependent lung, regional end-tidal and end-expiratory lung impedances as well as horizontal and vertical centers of ventilation will be recorded and calculated at 3 time points - before anesthesia induction, 5 minutes after lateral positioning of the patient and 90 minutes after lateral positioning. ABGs will be sampled to calculate aA gradient and Horovitz quotient at those time points as well as measured hemodynamic parameters (HR, BP, CI, SVI).

Primary endpoints for the study are nondependent/dependent tidal variation ratios measured at predefined time points and changes in ABGs. Secondary endpoints are number of postoperative pulmonary complications (defined as new onset of pneumonia during 28 days of followup), length of hospital stay and changes in hemodynamic parameters.

Inclusion Criteria:

• patients scheduled for nephrectomy, adrenalectomy or urterotomy surgery which will be performed in lateral decubitus position
• signed informed consent form

Exclusion Criteria:

• preexisting moderate to severe obstructive (GOLD score > 1) or restrictive lung disease (FVC < 85%)
• history of organ transplant
• disseminated malignant disease
• pregnancy