Skip to main content

Table 3 Composition of lung lining fluid in conducting airways and respiratory zone (from (Eixarch et al. 2010) and (Hastedt 2014))

From: Scope and relevance of a pulmonary biopharmaceutical classification system AAPS/FDA/USP Workshop March 16-17th, 2015 in Baltimore, MD

  Conducting airways Respiratory Zone
Principal lining fluid Mucus Surfactant
Composition of fluid layer 1 % inorganic salts 85 % phospholipids
1 % proteins 5 % cholesterol
2 % glycoproteins (mucins) 10 % surfactant proteins (e.g., SP-A, SP-B, SP-C, SP-D)
1 % lipids
95 % water
Layer thickness 3–15 μm (decreases in thickness in lower airways) ~0.07 μm
Approximate volume 10–30 ml 7–20 ml