Pleural effusion (PE) refers to the abnormal accumulation of fluid in the pleural space, a potential space between the visceral and parietal pleura that normally contains a thin film of fluid facilitating smooth lung movement during respiration. This fluid is produced and absorbed in tightly regulated amounts through a balance of hydrostatic and oncotic pressures, lymphatic drainage and mesothelial cell function. When the balance is disrupted—by alterations in fluid production, resorption or both—excess fluid accumulates, leading to PE. This can impair respiratory mechanics, reduce lung volumes and cause symptoms such as dyspnoea, chest pain and cough, depending on the volume and underlying mechanism of the effusion.

In this Journal of Physiotherapy Invited Topical Review, Mark Elkins outlines the aetiology, diagnosis and physiotherapy management of PE as well as future directions for research and practice.

PE can develop as a result of more than 50 pleural, pulmonary, cardiac and systemic disorders. Cancer is a common cause of PE, typically via metastatic involvement of the pleura. Impaired cardiac function, such as with heart failure, causes blood to back up into the pulmonary circulation, elevating hydrostatic pressure in the pulmonary capillaries and leading to fluid transudation into the pleural space, typically bilaterally. Pneumonia can lead to PE when the infection and associated inflammation extend from the lung parenchyma to the adjacent pleural space, increasing vascular permeability and resulting in the accumulation of exudative fluid. Mycobacterium tuberculosis can invade the pleural space from the lung, triggering a robust immune response that increases capillary permeability and impairs lymphatic drainage.

Symptoms of PE include dyspnoea/orthopnoea, pleuritic chest pain and cough, while signs consist of decreased breath sounds on auscultation, dullness to percussion, reduced tactile fremitus, reduced vocal resonance, tracheal deviation and asymmetrical chest expansion. Of these symptoms and signs, dullness to percussion is the most accurate for diagnosing PE, while absence of reduced tactile vocal fremitus means PE is less likely.

Evidence that physiotherapy interventions can prevent PE comes almost exclusively from trials involving patients undergoing cardiac surgery. Here, preoperative exercise and respiratory training help prevent some PEs, as do early mobilisation and continuous positive airway pressure. Electrical impedance tomography-guided breathing may also be effective. 
Several interventions are helpful in managing existing PEs. Continuous positive airway pressure helps them to resolve more quickly. In the meantime, if the PE is unilateral, lying on the contralateral side improves oxygenation. Breathing exercises and general exercise help to restore lung function and may contribute to reducing the length of stay in hospital.

For more information, read the entire Invited Topical Review.

This blog is a Physiotherapy Research Foundation (PRF) initiative.

Mark Elkins is a Clinical Associate Professor in the Faculty of Medicine and Health at the University of Sydney and the scientific editor of Journal of Physiotherapy.