The aim of this study is to assess the incidence of postoperative pulmonary complications in patients undergoing mechanical ventilation during general anesthesia for robotic surgery, to characterize current practices of mechanical ventilation and to evaluate a possible association between ventilatory parameters and postoperative pulmonary complications.

Research questions:

1. What is the incidence of PPC in patients undergoing mechanical ventilation during general anesthesia for robotic surgery?
2. Are the outcomes in patients undergoing robotic surgery dependent on ventilation practice and surgical positioning?
3. What is the incidence of patients at high risk for PPC undergoing robotic surgery

Methods:

In this international observational study, consecutive patients undergoing mechanical ventilation for robotic surgery are eligible for participation. Patients in participating centers will be screened on a daily basis. Patients undergoing mechanical ventilation for robotic surgery will be included during a 30-day period. The inclusion period will be flexible for participating centers and determined at a later stage together with the study-coordinator.

Time points of data collection:

1. Demographic data and baseline data, including severity scores (e.g. ASA) and ARISCAT, are collected from the clinical files on the day of surgery
2. Ventilation settings, gas exchange variables, positioning and vital parameters are collected hourly during surgery
3. Chest radiography data from available chest X-rays (i.e., no extra chest X-rays are obtained)
4. Predefined complications are recorded from medical chart until the first five postoperative days, discharge from hospital or death, whatever comes first
5. Length of hospital stay, and hospital mortality

Centres: The investigators aim to recruit 20 - 50 centers worldwide.

Ethics Approval: National coordinators will be responsible for clarifying the need for ethics approval and applying for this where appropriate according to local policy. Centres will not be permitted to record data unless ethics approval or an equivalent waiver is in place. The investigators expect that in most, if not every participating country, a patient informed consent is not be required.

Monitoring: Due to the observational nature of the study, a DSMB is not be necessary.

Study Population: Adult patients undergoing mechanical ventilation for robotic surgery.

Data Collection: Data will be collected at inclusion, during surgery and every day during five days, and day of hospital discharge. Data will be coded by a patient identification number (PIN) of which the code will be kept safe at the local sites. The data will be transcribed by local investigators onto an internet based electronic CRF.

Sample Size Calculation: A formal sample size will not be calculated, seen the largely descriptive character of this investigation. Data from 500 patients is expected to be collected, which will be sufficient to test the hypotheses.

Statistical Analysis: Patient characteristics will be compared and described by appropriate statistics. Student's t-test or Mann-Whitney U-tests are used to compare continuous variables and chi-squared tests are used for categorical variables. Data are expressed as means (SD), medians (interquartile range) and proportions as appropriate. Comparisons between and within groups are performed using one-way ANOVA and post-hoc analyses for continuous variables.

The primary analysis concerns the determination of the incidence of postoperative pulmonary complications in patients undergoing mechanical ventilation for robotic surgery.

To identify potential factors associated with outcome like development of postoperative pulmonary complications, or death, univariable analyses will be performed. A multi-level multivariable logistic regression model will be used to identify independent risk factors. A gradual approach will be used to enter new terms into the model, with a limit of p < 0.2 to enter the terms. Time to event variables will be analyzed using Cox regression and visualized by Kaplan-Meier.

Organization: The study is conducted by the PROtective VEntilation Network (PROVENet). National co-ordinators will lead the project within individual nations and identify participating hospitals, translate study paperwork, distribute study paperwork and ensure necessary regulatory approvals are in place. They provide assistance to the participating clinical sites in trial management, record keeping and data management. Local coordinators in each site will supervise data collection and ensure adherence to Good Clinical Practice during the trial.

Inclusion Criteria:

• Age ≥ 18 years
• All surgical procedures performed under general anesthesia for robotic surgery, including head and neck operations, chest, cardiac, and abdominal surgeries

Exclusion Criteria:

• Any procedure during pregnancy
• Procedures outside of the operating room

Adult patients undergoing mechanical ventilation during general anesthesia for robotic surgery

The data will be available for substudies suggested by members of the collaboration.

After the publication of the main manuscript

The data will be available for substudies suggested by members of the collaboration.