Study objective: The mechanism of action of potential
mucoactive agents could relate to effects on the mucociliary apparatus
or to direct effects on the secretions. The purpose of this study was
to determine the in vitro effects of several agents on
the properties of mucus simulants and sputum collected from 30 adults
with stable chronic bronchitis.
Design: Sputum or
simulants were analyzed untreated and after the addition of the test
agent at 1:5 volume to volume ratio for a contact period of 60 s.
The concentrations of the agents were as follows: guaifenesin, 20
mg/mL; iodinated glycerol, 3 mg/mL; surfactant (Exosurf; Glaxo
Wellcome; Research Triangle Park, NC) containing 13.5 mg of
phospholipid per milliliter; albuterol, 5 mg/mL; and amphibian
Ringer’s solution (ARS) as a control. Dynamic viscoelasticity and
surface mechanical impedance were measured in a magnetic
microrheometer. Cohesiveness was measured using a filancemeter. The
wettability of a hydrophilic surface was measured using an image
processing system. The mucociliary transportability of sputum was timed
on the frog palate, and cough transportability (CTR) was measured in a
Results: When compared to sputum that
had no test agent or ARS added, all agents reduced sputum elasticity
G′, with surfactant, albuterol, and guaifenesin significant at
p < 0.001. As well, guaifenesin (p = 0.006), albuterol
(p = 0.003), and surfactant (p = 0.02) decreased surface mechanical
impedance (frictional adhesiveness) compared to untreated sputum.
However, there were no significant changes in wettability, hydration,
cohesiveness, or CTR with any agent, and there were no significant
changes in the properties of sputum or simulants treated with test
agents when compared to those treated with ARS. Guaifenesin
irreversibly disrupted mucociliary transport when applied directly to
the frog palate.
Conclusions: These agents appear to
have a minimal direct action on sputum in vitro,
suggesting that at the concentrations studied, these agents do not have
a significant beneficial effect on either the mucociliary
transportability or CTR of chronic bronchitis sputum. However,
there could be an effect of some of these agents after oral
administration, especially if there is a secondary effect of the agent
on an effector cell.