Firefighting Acutely Increases Airway Responsiveness

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Abstract
The acute effects of the products of combustion and pyrolysis on airway responsiveness among firefighters are poorly documented. To study this relationship, spirometry and methacholine challenge testing (MCT) were performed on 18 active Seattle, Washington [USA] firefighters before and 5 to 24 h after firefighting. Body plethysmography was used to measure changes in specific airway conductance (SGaw), and results of MCT were analyzed using PD35-SGaw, the cumulative dose causing a 35% decrease in SGaw. Subjects who did not react by the end of the protocol were assigned a value of 640 inhalational units, the largest cumulative dose. Fire exposure was defined as the total time (hours) spent without a self-contained breathing apparatus at the firesite and was categorized as mild (< 1 h, n = 7), moderate (1 to 2 h, n = 5), or severe (> 2 h, n = 6). Mean age of the 18 firefighters was 36.7 .+-. 6.7 yr (range, 25 to 51) with a mean of 9.1 .+-. 7.9 active years in the trade (range, zero to 22). None was known to be asthmatic. After firefighting, FEV1 % predicted (%pred) and FEF25-75% pred significantly decreased by means of 3.4 .+-. 1.1% and 5.6 .+-. 2.6%, respectively. The mean decline in PD35-SGaw could not be explained by decrements in prechallenge SGaw, FEV1, or FVC. Analysis of variance revealed that the percent change in PD35-SGaw was greatest in those with moderate exposure (81.5%, p < 0.05) and was not related to smoking (p = 0.43) or years in the trade (p = 0.56). Firefighting is associated with an acute decrease in FEV1% pred and FEF25-75 %pred and with an acute increase in airway responsiveness among firefighting.