The purpose of this study, is to clarify whether there is benefit from the perioperative use of HFNC in thoracic surgeries, from intubation to the postoperative period, evaluating hipoxemia during orotracheal intubation, immediate complications after intubation, mortality and in-hospital complications.

High-flow Nasal Catheter (HFNC) compared to oxygenation conventional during the perioperative period of patients undergoing thoracic surgery The increase in surgeries performed worldwide, with today an estimate of more than 300 million surgeries/year, makes us increasingly need knowledge and strategies to improve perioperative care. Complications in this period are responsible for an increase in morbidity and mortality of patients, reducing the effectiveness of the surgical treatment, mainly in developing countries. The use of a nasal cannula high-flow (HFNC) oxygen during the perioperative period offers a promising technique to improve the lung function of these patients, enabling better outcomes.

The purpose of this study, therefore, is to clarify whether there is benefit from the perioperative use of HFNC, in thoracic surgeries, from intubation to the postoperative period, evaluating mortality and in-hospital complications.

Primary and secondary objectives

Main goal

• To evaluate the incidence of in-hospital pulmonary complications in 30 days in participants submitted to the use of HFNC in the perioperative period of participants undergoing thoracic surgery, when compared to the use of conventional oxygen therapy.
• To evaluate in-hospital postoperative mortality within 30 days.

Secondary objectives

• Assess the incidence of hypoxemia during orotracheal intubation and extubation
• Assess the incidence of immediate complications after intubation and extubation (desaturation, failure of intubation/ extubation)

It will be a randomized, non-blinded, single-center clinical trial. Participants (older than 18 years old) who undergo thoracic surgery and who are at surgical risk for postoperative complications with ARISCAT > 26 (risk score for pulmonary complications) will be allocated consecutively and randomized to participate in the intervention group or control, receiving written informed consent to the study and interventions. The study will be carried out at Hospital Tacchini, from July 2023 to June 2024.

Control group will receive conventional oxygen therapy, and the intervention group will receive HFNC therapy at induction of anesthesia and postoperatively, after extubation.

Oxygenation will be performed, according to the randomization, in the control group, by mask facial, with 100% oxygen and flow of 10 L.min-1. The intervention group will receive oxygenby 100% HFNC with a flow of 40 L.min-1 being increased to 70 L.min-1 during the periodof apnea.

A rapid sequence of orotracheal intubation will be performed, considering the time of apnea the moment of disappearance of the capnography line until the first ventilation after tube placement. Difficulties and complications in carrying out this step will be described. A oxygen saturation will be measured before the start of pre-oxygenation and will be considered hypoxemia, any measurement below 90% saturation, during the initiation of the rapid sequence intubation up to 5 minutes after it, in both groups. All participants will be intubated according to current orotracheal intubation guidelines. After surgery, participants who are extubated in the operating room or in the intensive care unit, will remain in the control and intervention groups and will receive therapy for conventional oxygen or HFNC, respectively. The fraction of inspired oxygen (FiO2) will be titrated until pulse oximetry is above 95%, which is also reduced to the level minimum, to achieve this objective. In the control group, oxygen will be offered through a nasal catheter or face mask and those in the intervention group will receive oxygen through HFNC with flows adjusted between 30 and 50 L.min-1, depending on the respiratory rate (less than 16) and the patient comfort.

Data and statistics analysis strategy The data, after being collected, will be expressed as mean and standard deviation or absolute frequency and relative. Data normality will be tested by the Kolmogorov-Smirnov test. The difference Significant difference between groups will be analyzed using Student's t test for data for parametric data and for non-parametric data the Wilcoxon test will be used. The program used will be the Statistical Package for the Social Sciences, version 20 (SPSS Inc., Chicago, IL,USA) and the significance level adopted will be p<0.05.

Calculation and/or justification of the sample size According to the literature, patients undergoing thoracic surgery may present severe complications such as postoperative hypoxemia in up to 30% of cases, after extubation. Based on the literature review, the sample calculation should be 45 patients for each group. For the sample calculation, we considered the value of β of 20% and α of 5%.

. Using a effect size (calculated from the article data) of 0.6, a statistical power of 80% and a significance level of p<0.05 (or 5%), the investigators obtained as a result the n of 90 volunteers per group (final sample, excluding possible losses). The G*Power program version 3.1.9.2 for Windows (Franz Faul, University Kiel, Germany) was used to perform the calculation.

Inclusion Criteria:

• All patients over 18 years of age who will undergo elective thoracic surgery and who have an ARISCAT score > 26.

Exclusion Criteria:

• Patients who need urgent/emergency surgery, pregnant women, who do not have an ARISCAT score > 26 and those who refuse to participate in the study.