• Michele Umbrello, Giovanni Mistraletti, Andrea Galimberti, Ilaria R Piva, Ottavia Cozzi, and Paolo Formenti.
• Department of Anaesthetics and Intensive Care, Ospedale San Paolo - Polo Universitario, ASST Santi Paolo e Carlo, Milan, Italy. paolo.formenti@asst-santipaolocarlo.it.
• Crit Care Resusc. 2017 Mar 1; 19 (1): 64-70.

BackgroundPleural effusion adversely affects the pressuregenerating capacity of the diaphragm. It uncouples the lung and chest wall, which may result in diaphragmatic dysfunction. Information on the effects of effusion drainage on diaphragmatic function is limited, but several studies report relief of dyspnoea after drainage, which was attributed to improved diaphragmatic mechanics, even if this issue was never formally addressed.ObjectiveTo investigate the effect of drainage of unilateral pleural effusion on diaphragmatic function.Design, Setting And PatientsIn a prospective twostep protocol (at baseline and after drainage of effusion), we conducted a spontaneous breathing trial in fourteen critically ill, mechanically ventilated patients undergoing pressure support ventilation.Main Outcome MeasuresWe used ultrasonography of the ipsilateral hemidiaphragm to evaluate and record respiratory displacement and thickening during tidal and maximal breathing efforts. We recorded and analysed airway pressures, respiratory system compliance, vital capacity, indices of respiratory effort and arterial blood gases.ResultsAfter drainage of the effusion, the respiratory rate decreased and tidal volume increased, but haemodynamic parameters were unaffected and oxygenation levels showed a non-significant increase. Drainage was associated with significant decreases in indices of respiratory drive and the maximal pressure generated by the respiratory muscles, as well as an increased compliance of the respiratory system. Diaphragmatic displacement and thickening significantly increased after drainage. We found there was a significant correlation between the volume of the effusion drained and the increase in tidal diaphragmatic thickening.ConclusionsDrainage of a unilateral pleural effusion during weaning from mechanical ventilation improves diaphragmatic contractile activity and respiratory system performance.

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