The purpose of this prospective observational study is to assess perioperative changes in lung aeration after lung resection surgery using lung ultrasound, and to explore their relationship with oxygenation, inflammatory biomarkers, cardiac stress markers and diaphragmatic function.

Postoperative pulmonary complications are common after lung resection surgery and are associated with worse clinical outcomes. Lung ultrasound (LUS) is a bedside, non-invasive and repeatable imaging technique that can detect regional changes in lung aeration. These changes may reflect postoperative loss of aeration related to one-lung ventilation, surgical manipulation, lung collapse and re-expansion, inflammatory response, diaphragmatic dysfunction or other perioperative mechanisms.

This is a prospective, single-centre, observational pilot study including consecutive adult patients scheduled for elective lung resection surgery under one-lung ventilation. Lung ultrasound was performed at three predefined time points: before surgery (T1), 30 minutes after extubation (T2), and 24 hours after surgery (T3). Each hemithorax was divided into six regions: anterior, lateral and posterior areas, each subdivided into upper and lower zones. For each examination, the most pathological ultrasound finding in each area was recorded. A semiquantitative lung ultrasound score was calculated to assess lung aeration over time, both globally and separately for the operated and non-operated lung. Corrected LUSS values were used to compensate for the loss of areas after surgery.

At the same predefined time points, oxygenation, NT-proBNP and plasma inflammatory biomarkers, including IL-6, IL-10 and TNF-α, were assessed. Bedside transthoracic echocardiography and diaphragmatic ultrasound were also performed as exploratory analyses to evaluate possible cardiovascular and diaphragmatic mechanisms associated with postoperative loss of lung aeration.

The primary objective of the study is to assess perioperative changes in lung aeration after lung resection surgery using LUS. Secondary objectives are to describe the regional distribution of LUS findings, compare the operated and non-operated lung, assess the feasibility of repeated perioperative LUS examinations, and explore the relationship between LUS changes and oxygenation, inflammatory biomarkers, cardiac stress markers and diaphragmatic function.

Inclusion Criteria:

• Age > 18
• ASA I-III
• Non-small cell lung neoplasm
• Elective lobectomy
• Under one-lung ventilation

Exclusion Criteria:

• pregnancy
• Diagnosed pulmonary fibrosis
• Scheduled surgery limited to biopsy
• Surgery that includes resection of the thoracic wall or the diaphragm
• Predicted FEV1 < 40%
• Neoplasm metastasis
• Obesity class II or more (BMI ≥ 35 kg/m^2)
• Risk of malnutrition CONUT score > 1
• Hemoglobin < 10 g/dl
• Chronic kidney failure: glomerular filtration < 60 ml/min/m^2, nephrectomy, kidney transplantation
• Treatment with corticosteroids or immunosuppressive agents 3 months before surgery
• Transfusion of blood products during the previous 10 days
• Heart failure (New York Heart Association Functional Class 3 or 4) during the week before surgery.
• Heart valve diseases over stage B of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines 2014
• Previously documented elevated left atrial pressure or cardiac disease associated with elevated left-sided filling pressures.

Patients scheduled for elective lung resection surgery at a tertiary referral hospital.