Optical scanning to measure airway surface liquid volume. (A) Differentiated primary HBE cell cultures were imaged with an optical scanner. As shown in the top panel, non-cystic fibrosis HBE develop a liquid meniscus that surrounds the culture insert. Conversely, this fluid is absent in HBE cultured from cystic fibrosis donors. A magnified view is shown on the right to demonstrate the liquid meniscus that surrounds each individual culture. (B) AUC/ASL volume calibration curve. Increasing volumes of Ringer’s solution were applied to the apical surface of differentiated HBE cultures, and the area under the curve was measured as described. Data shown are mean AUC vs. applied ASL volume. n = 6.