Breathing dry air causes acute epithelial damage and inflammation of the guinea pig trachea.

Drying and cooling of the airways mucosa caused by respiratory water loss may be responsible for exercise- and hyperventilation-induced asthma. Therefore we designed this study to investigate whether breathing dry air is capable of causing structural changes of the airways mucosa. Anesthetized guinea pigs breathed spontaneously through a tracheostomy either dry (n = 15) or water-saturated (n = 12) air at approximately 38 degrees C for 30 or 60 min, during which time total pulmonary resistance (TPR) was measured. Immediately afterward, the animals were killed and the lungs and airways were prepared for histological examination (light microscopy, transmission electron microscopy, and scanning electron microscopy). With dry as well as humid air, there was no change in TPR or in the structure of the main bronchi and lung parenchyma. With humid air the tracheal mucosa was normal in six guinea pigs and exhibited minor changes of the ciliae in eight and localized epithelial damage on light microscopy in the remaining animal. With dry air we found widespread loss of the ciliae on scanning electron microscopy in 10 of 12 animals, associated with detachment or sloughing of the epithelium, subepithelial vascular congestion, edema, and cellular infiltration on light microscopy. Our data demonstrate that a short exposure of the trachea to dry air causes marked epithelial lesions and local inflammation.