Pathophysiological Effects of Intrapleural Pressure Changes During Therapeutic Thoracentesis

Research project objectives. The project includes eight research hypotheses and eight corresponding study objectives. The most relevant objectives are: * Analysis of lung function and gas exchange parameters in relation to the removed pleural fluid volume and intrapleural pressure changes. * Evaluation of changes in lung and chest wall compliance and related changes in work of breathing during therapeutic thoracentesis and pleural fluid withdrawal. * Study of the relationship between intrapleural pressure changes and cardiac function assessed by echocardiography and alterations in serum natriuretic peptide A and B concentration. * Comparative analysis of the reliability of the volume-pressure curve slope prediction based on different variables measured before thoracentesis and real measurements of ventilation and intrapleural pressure during thoracentesis. 2\. Research methodology The study will be performed in 60 patients with pleural effusion planned for therapeutic thoracentesis. Studies before thoracentesis: body plethysmography, spirometry, lung diffusion capacity (DLCO), arterial blood gases, 6 minute walk test, echocardiography, serum natriuretic peptide concentration. Evaluation during thoracentesis: continuous measurement of tidal breathing and respiratory rate, measurement of removed pleural fluid volume and intrapleural pressure, transcutaneous measurement of PO2 and PCO2. Pleural catheter will be retained for the next 48hours to enable fluid drainage and intrapleural pressure measurement after completion of thoracentesis. Monitoring during 48-hrs after thoracentesis: pre-thoracentesis measurements will be repeated in specific time points and compared in two subgroups (active physiotherapy to improve lung re-expansion and passive lung re-expansion). Intrapleural pressure will be measured 24 and 48 hours after thoracentesis. Then, the catheter will be removed. Analysis.Signal analysis and visual multidimensional analysis performed with the use of