Bronchoalveolar_lavage_fluid
Bronchoalveolar lavage (BAL), also known as bronchoalveolar washing, is a diagnostic method of the lower respiratory system in which a bronchoscope is passed through the mouth or nose into an appropriate airway in the lungs, with a measured amount of fluid introduced and then collected for examination. This method is typically performed to diagnose pathogenic infections of the lower respiratory airways[1][2][3] (e.g. pneumonia[4][5][6] and COVID-19[7][8]), though it also has been shown to have utility in diagnosing interstitial lung disease.[9] Bronchoalveolar lavage can be a more sensitive method of detection than nasal swabs in respiratory molecular diagnostics, as has been the case with SARS-CoV-2 where bronchoalveolar lavage samples detect copies of viral RNA after negative nasal swab testing.[10][11]
In particular, bronchoalveolar lavage is commonly used to diagnose infections in people with immune system problems,[12] pneumonia in people on ventilators,[5][6] and acute respiratory distress syndrome (ARDS).[3][13] It is the most common method used to sample the epithelial lining fluid (ELF) and to determine the protein composition of the pulmonary airways.[3][13]
BAL has even been used therapeutically to remove mucus (sputum), improve airway ventilation, and reduce airway inflammation in conditions such as chronic obstructive pulmonary disease (COPD)[14] and pediatric Mycoplasma pneumonia.[15] A much more intense version involving up to 50 liters of fluid is called whole lung lavage (WLL) and is used to treat pulmonary alveolar proteinosis (PAP).[16][17][18] When conditions disallow WLL, an endoscopic BAL can be used as a bridging procedure.[11]