Lung function and bronchial hyperreactivity following exposure to four different temperatures and relative humidities.

Seven asthmatic patients were exposed to four different climatic conditions in a climate chamber. The four conditions were: 15 degrees C/30% relative humidity (RH), 15 degrees C/70% RH, 30 degrees C/30% RH and 30 degrees C/70% RH and the exposure time was 4 hours. Before and after the exposure the following lung function parameters were measured: PEF, FEV1, RV and TLC. After each exposure a bronchial challenge with histamine was performed by the doubling-dose principle. The results indicated no difference in lung function after exposure to the "extreme" conditions in this study (i.e. 15 degrees C/30% RH and 30 degrees C/70% RH, water content 3.5 and 19 g/kg dry air, respectively), while a decrease in RV and TLC was seen after exposure to the "middle" conditions (i.e. 15 degrees C/70% RH and 30 degrees C/30% RH, water content 7.5 and 8 g/kg dry air, respectively). No change in ventilatory capacity was seen, and the bronchial hyperactivity also remained unchanged. During the 4 hours exposure, measurements of FEV1 and PEF also remained constant. It is concluded that this kind of exposure is without great effect on the asthmatics condition.