The influence of varying air humidity on mucociliary activity.

The influence of varying humidity levels in the air surrounding the mucous membrane of rabbit tracheae has been investigated in vitro at 34°C, 37°C and 40°C. The following results were obtained: (1) The average mucociliary wave frequency was linearly reduced following decreasing levels of relative humidity (r.h.) from 90% to 20%. (2) A temperature of 40°C was more detrimental to the mucociliary function than that of 34°C and 37°C (body temperature) at decreasing levels of r.h. (3) At decreasing levels of r.h. the duration of experiments with preservation in recordable activity (“mucociliary survival time”) was significantly shorter (p < 0.05) between 50 % and 40 % r.h. than between 60 % and 50 % r.h.