Bronchial responsiveness to eucapnic hyperventilation and methacholine following exposure to organic dust.
OBJECTIVE
Inhalation of dust in a swine confinement building causes an intense airway inflammatory reaction in the airways and increased bronchial responsiveness to methacholine. The aims of the present study were to investigate whether exposure to organic dust also influences bronchial responsiveness to an indirect stimulus, and to assess the duration of increased postexposure bronchial responsiveness.


METHODS
Twenty-two healthy nonatopic, nonsmoking subjects were exposed to dust for 3 h in a swine confinement building. Lung function was assessed, and either a methacholine bronchial provocation (n = 11) or a challenge with eucapnic hyperventilation of dry air (n = 11) was performed before exposure and at 7 h, 1 week, 2 weeks, and 4 weeks after exposure.


RESULTS
Vital capacity and FEV(1) decreased 3% and 6%, respectively (p < 0.001), and airway resistance increased 15% (p < 0.05) after exposure. The median provocative dose of methacholine causing a 20% decline in FEV(1) fell from 1.38 mg (25th to 75th percentiles, 0.75 to 7.20 mg) before exposure to 0.18 mg (0.11 to 0.30 mg) after exposure (p = 0.004). Corresponding values for the dose-response slope were 15.3%/mg (2.88 to 25.3%/mg) and 100.2%/mg (2.1 to 27.3%/mg), respectively (p = 0.01). Bronchial responsiveness to eucapnic hyperventilation was not affected by the exposure: FEV(1) fell 4.3% (- 7.2 to - 1.8%) before and 4.8% (- 6.7 to - 1.6%) after exposure (p = 0.72). One week after exposure, the bronchial responsiveness to methacholine was normalized.


CONCLUSIONS
The bronchial responsiveness to methacholine but not to dry air increases after exposure to swine house dust. Thus, exposure to organic dust induces increased bronchial responsiveness with different characteristics from that frequently found in asthma.
Sundblad
Britt-Marie
BM
Program for Respiratory Health and Climate, National Institute for Working Life, Stockholm, Sweden. Britt-Marie.Sundblad@niwl.se
Palmberg
Lena
L
Larsson
Kjell
K
D000328:Adult; D000818:Animals; D001985:Bronchial Provocation Tests / Q000379:methods*; D016085:Bronchoconstrictor Agents / Q000009:adverse effects*; D016001:Confidence Intervals; D004391:Dust / Q000009:adverse effects*; D005260:Female; D006801:Humans; D006985:Hyperventilation; D008297:Male; D016210:Methacholine Chloride / Q000009:adverse effects*; D016273:Occupational Exposure; D012129:Respiratory Function Tests; D013552:Swine
D016085:Bronchoconstrictor Agents; D004391:Dust; D016210:Methacholine Chloride