SFTPB and acute respiratory distress syndrome: Our results can be summarized as follows: 1) DSPC and SP-B turned over with different kinetics in the airways both in human adults with normal lungs and in patients with ARDS/ALI, 2) in patients with ARDS/ALI in spite of the low concentration of DSPC and SP-B in tracheal aspirates, the fractional synthesis rate of DSPC increased, while that of SP-B did not change significantly.