Air humidity and mucociliary activity.

The relationship between varying humidity levels in the surrounding air and the mucociliary activity in rabbit trachea has been investigated. At a relative humidity (R.H.) above 70% the risk for ciliestasis is very small in the temperature range between 34 C and 40 C. At 37 C ciliestasis is not obtained until a relative humidity (R.H.) of 50% has been reached. The critical border is reached already at 60% R.H. if the temperature is 40 C. At 37 C and a decrement from 90% to 60% R.H. the mucociliary wave frequency was reduced by 30%, but at 40 C the corresponding reduction was 60%.