RELATIONSHIP BETWEEN THE HUMIDITY AND TEMPERATURE OF INSPIRED GAS ANDTHE FUNCTION OF THE AIRWAY MUCOSA

Objective: To review the available literature on the relationship betw een the humidity and temperature of inspired gas and airway mucosal fu nction. Data Sources: International computerized databases and publish ed indices, experts in the field, conference proceedings, bibliographi es. Study Selection/Data Extraction: Two hundred articles/texts on res piratory tract physiology and humidification were reviewed. Seventeen articles were selected from 40 articles for inclusion in the published data verification of the model. Selection was by independent reviewer s. Extraction was by consensus, and was based on finding sufficient da ta. Data Synthesis: A relationship exists between inspired gas humidit y and temperature, exposure time to a given humidity level, and mucosa l function, This relationship can be modeled and represented as an ins pired humidity magnitude vs, exposure time map. The model is predictiv e of mucosal function and can be partially verified by the available l iterature. It predicts that if inspired humidity deviates from an opti mal level, a progressive mucosal dysfunction begins. The greater the h umidity deviation, the faster the mucosal dysfunction progresses. Conc lusions: A model for the relationship between airway mucosal dysfuncti on and the combination of the humidity of inspired gas and the duratio n over which the airway mucosa is exposed to that humidity is proposed . This model suggests that there is an optimal temperature and humidit y above which, and below which, there is impaired mucosal function. Th is optimal level of temperature and humidity is core temperature and 1 00% relative humidity. However, existing data are only sufficient to t est this model for gas conditions below core temperature and 100% rela tive humidity. These data concur with the model in that region. No stu dies have yet looked at this relationship beyond 24 hrs. Longer exposu re times to any given level of inspired humidity and inspired gas temp eratures and humidities above core temperature and 100% relative humid ity need to be studied to fully verify the proposed model.