The research will be retrospective, and will include all patients who were admitted during 2020 and 2021 in the COVID-19 ICU of University Hospital Center Osijek due to pneumonia caused by the Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The association of chest x-ray infiltrate evolution with changes in laboratory inflammatory parameters and respiratory function parameters will be examined.

The research will be retrospective, and will include a review of medical history of all patients admitted in the COVID-19 ICU of the University hospital Osijek during 2020 and 2021. Associated comorbidity, hospital admission date, intubation date, mechanical ventilation, extubation, discharge, and patient final outcome will be recorded for each patient. By analyzing X-rays of the lungs by radiology specialists, inflammatory infiltrates in the lungs will be quantified via the Brixia system, during hospital admission, admission to the Respiratory Center, and during treatment at the Respiratory Center. All patients will have their Sequential Organ Failure Assessment (SOFA) and/or Acute Physiology and Chronic Health Evaluation (APACHE II) values calculated upon admission. Inflammatory parameters (c-reactive protein (CRP), procalcitonin (PCT), interleukine-6 (IL-6), ferritin), red blood cell count, leukocytes, blood urea nitrogen (BUN), arterial blood gases and ventilation parameters on admission to the hospital, admission to the ICU, and on several occasions during treatment in the ICU will be analysed. Also, empirical use of antibiotics, the occurrence of bacterial superinfections, sepsis and organic failure will be noted.

Inclusion Criteria:

• Pneumonia caused by SARS-CoV-2 virus
• Admission to the ICU COVID-19 unit

Exclusion Criteria:

- Patients with lung tumors or history of lung resection

All patients treated in ICU COVID-19 with a diagnosis of pneumonia will be analyzed retrospectively.