Healthy fluid drained from the lungs during a thoracentesis is light yellow in color and clear, notes Lab Tests Online. Red fluid contains red blood cells. Cloudy fluid is indicative of high protein levels and may be a sign of contamination with white blood cells or microorganisms.
A thoracentesis is performed when excess fluid accumulates between the lungs and the chest cavity, explains Healthline. The term for this condition is pleural effusion. It causes shortness of breath and chest pain due to lung compression, explains Remedy Health. A test of this fluid is known as pleural fluid analysis, as Healthline describes. The pleural fluid analysis can help to determine if the condition is caused by cardiac failure, infection, disease or trauma.