Assisting With Thoracentesis

Pleural fluid sits between the visceral pleura covering the lung and the parietal pleura lining the chest wall. A small amount lubricates lung movement. An effusion develops when fluid enters this space faster than lymphatic vessels can clear it. The mechanism matters because an effusion is a finding, not a diagnosis. Increased hydrostatic pressure can push fluid outward, as in heart failure. Low oncotic pressure can reduce the pull that normally keeps fluid in the circulation. Inflammation, infection, malignancy, bleeding, and impaired lymphatic drainage can also fill the pleural space. Thoracentesis removes fluid with a needle or catheter. It may be performed to: - obtain a diagnostic sample; - relieve dyspnea caused by a large or symptomatic effusion; - assess whether the lung re-expands after drainage; or - investigate suspected pleural infection. Removing fluid may improve comfort and ventilation, but it does not automatically treat the condition that created the effusion. A patient with heart-failure-related fluid overload, for example, may also need treatment directed at the underlying cardiac problem. A patient with infected pleural fluid may require an intercostal drain...