Effects of gravity on tracheal mucus transport rates in normal subjects and in patients with cystic fibrosis.

A noninvasive, radionuclide imaging technique for measuring the rate of mucus clearance 
in the trachea (RT), was used to study gravitational effects on 
mucus clearance in 13 patients with cystic fibrosis (CF), average age 
17 years; 7 normal, nonsmoking adults, average age 26 years; and 
a normal subject who was recovering from an acute upper respiratory 
tract infection (URTI). In the upright position, nine of the CF 
patients and the subject with URTI demonstrated abnormal tracheal mucus clearance 
which approached normal when they were placed in 25 degrees headdown 
position. The normal subjects and two of the CF patients showed 
no significant difference in the RT measured in the two positions. 
The results of the study indicate that the force of gravity 
can be a major influence on tracheal mucus clearance in CF 
and URTI subjects. This conclusion supports the use of postural drainage 
as an effective form of therapy in patients with cystic fibrosis. 
