Data collection
Data were retrospectively extracted from medical charts by three investigators (M.T., F.L. and P.D.). Baseline data included medical history, age, main complaints and clinical findings at hospital admission. Tachycardia was defined according to the age based on the following thresholds: 180 beat per minute (bpm) for infants, and 160 bpm for children aged 1-16-years. The increased work of breathing was documented as per medical notes, based on a subjective assessment by the treating physician (no scale measurement).
Data collected during the hospital stay included the use of at least one dose of corticosteroid (prednisone or methylprednisolone) as part of the management of the pleural effusion, the use of respiratory support techniques (high-flow oxygen therapy, noninvasive ventilation, mechanical ventilation), the number of chest imaging exams and the use of painkillers. We also collected data to characterize the pleural effusion, including the time of diagnosis, the presence of fibrin in the effusion (according to the chest ultrasound protocol), the time and type (needle thoracocentesis, chest tube) of evacuation (if any), the duration of drainage (if any), the total volume drained, the use of intrapleural fibrinolysis, as well as the leucocyte count of the pleural effusion. We also collected the total duration of fever (defined as a temperature ≥ 38°C), the highest C-reactive protein (CRP) level as well as the highest leukocyte count. Finally, we recorded the duration of the hospital stay.