Dear Sir or Madam,

Thank you for showing interest in this study.

The PROTHOR trial is directed to optimize mechanical ventilation in patients undergoing anesthesia for thoracic surgery. We, the trial investigators, aim at minimizing pulmonary complications after a surgical intervention.

While under anesthesia, the patient is not able to breathe himself. Instead, a machine will take over the work of breathing for the patient. This is called 'mechanical ventilation'. Pressurized air flows into the lungs, resulting in a breath. Then the pressure is reduced, allowing the lungs to exhale. Due to completely relaxed abdominal muscles, the lung actually exhales more air than it would in an awake, non-anesthetized state. This causes parts of the lung to collapse, which in turn impedes normal lung function and can lead to complications. Thoracic surgery patients have a very high risk for impaired lung function, not only during surgery, but especially in the period after the operation. The anesthesiologist can improve airflow to all parts of the lung by administering a constant positive pressure in both in- and exhalation. This positive pressure may not only improve lung function during general anesthesia, but also in the period after surgery, during recovery. Mechanical ventilation with higher positive pressure may reduce the possibility of pulmonary complications such as pneumonia or low blood oxygen (called 'hypoxia'). This could improve well-being after surgery as well as even shorten hospital stay.

As of yet, a higher continuous positive pressure is not in routine clinical use because it is not known how high it actually needs to be to provide healthy, safe anesthesia. Current practice is to use a relatively low pressure, deliberately allowing parts of the lung to collapse and maintaining only a minimum of lung function. On the other hand, a higher pressure will improve the distribution of air in the lung, but may also cause blood pressure to drop. In some cases this requires extra medication.

The main objective of this trial is to find out, whether a higher continuous positive pressure during mechanical ventilation can influence lung-associated complications.

First, an anesthesiologist will use special criteria to determine if the patient is a suitable candidate for the trial. By giving written consent, the patient can enroll. Before surgery, the trial doctor will take the patient's history and vital signs, conduct a physical examination and draw blood. After all the standard preparations have been made, general anesthesia will begin and the patient will receive mechanical ventilation with either a higher or lower pressure for the entire duration of the operation. The patient will be assigned either the high or low pressure strategy by a randomizing computer algorithm - patients and doctors cannot influence this decision. Moreover - as part of the study, the patient will not know about the modality of ventilatory management he received. Directly before the end of anesthesia, the trial doctor will draw blood one more time. While the patient is recovering, another trial doctor will visit the patient every day for the first five days and on the day before hospital discharge. The physician will also call the patient by telephone after at least three month after surgery. The trial has no influence on the length of the hospital stay and does not include any additional tests after the patient goes home. The treatment will follow international standard patient guidelines.

If the patient decides to take part in the trial, he/she will be asked to:

• Read and sign an informed consent form
• Schedule and agree to follow-up telephone call
• Answer additional questions at follow-up
• Report any problems to your treating physician

The probability that you will be assigned to the group with the higher respiratory pressure or the group with the lower respiratory pressure is equal, 50% for both cases. A particular advantage for all patients participating in this study is that they can benefit from extended monitoring during and after the operation. Nevertheless, there are different risks and benefits for both groups. If you are assigned to the low-pressure ventilation group, you will be given the ventilation treatment that is preferred by most of the anesthesists all over the world. During low pressure ventilation, the oxygen content in the blood may be too low so that the respiratory gas mixture or respiratory pressure has to be adapted. A particular advantage of this form of ventilation is that the circulation is somewhat more stable. During ventilation with higher pressure, the air passages may well be held open, which is likley to help the transfer of oxygen. However, a transient drop in blood pressure may occur, which can be easily treated by the administration of specific drugs. These drugs occasionally lead to a reduction of the heart rate, which does not cause damage. If a situation develops with impaired lung function or depression of the cardiocirculatory system, the applied ventilation pressure will be adapted to restore proper function. Physical examination does not involve invasive or painful procedures. The study-related blood samples are, as far as possible, linked to the routine blood collection or carried out via existing vascular access. In the case of study-related venipunctions, there is a risk of infections, hematoms and nerve damage in the area of the puncture site or its surroundings. In the blood samples, laboratory tests are carried out, which allow a statement on the function of different organs, including the lungs. Blood samples will be stored in the Department of Anesthesia and Intensive Care (Director: Prof. T. Koch) of the University Hospital Carl Gustav Carus in Dresden and destroyed after 10 years.

All research protocols that are conducted in patients are reviewed carefully by an independent research ethics committee, which aims to protect your safety, rights, well-being and dignity. This trial has been approved by the ethics committee that is responsible for the corresponding hospital.

The data collected in the study will be saved both electronically and in paper form for at least 10 years in the coordination center for clinical Trials (KKS) in Dresden and partly also in the Department of Anesthesia and Intensive Care of the University Hospital Carl Gustav Carus Dresden (Director: Prof. Dr. Dr. T. Koch). This time period can be changed by new laws of the Federal Republic of Germany. Data access is granted to the staff of the KKS Dresden and the investigators of the study in Dresden, whereby all parties must comply with the german data safety and privacy regulations. For this case your consent is required. The data will be processed by special software and statistically evaluated. In data processing, the identity of the patients is encrypted by means of a number code (pseudonymization). This code can be passed on to the relevant monitoring authorities. For inspection purposes the access to the encrypted data can be granted, but the person entitled to access is obliged to maintain secrecy.It is planned to publish the study results in one or more scientific journals. In this case, due to the pseudonymization conclusions on individual patients will not be possible.You have the right to access and to correct your data collected in the study. Informing your family practitioner about participation in the study is desirable, but requires your explicit consent.