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Bronchial Responsiveness to Eucapnic Hyperventilation and Methacholine Following Exposure to Organic Dust^*

^* From the Program for Respiratory Health and Climate, National Institute for Working Life, Stockholm, Sweden.

Correspondence to: Britt-Marie Sundblad, BSc, Program for Respiratory Health and Climate, National Institute for Working Life, S-11279 Stockholm, Sweden; e-mail: Britt-Marie.Sundblad{at}niwl.se

Study 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.

Design: 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 FEV₁ 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 FEV₁ 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: FEV₁ 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.

Key Words: bronchial provocation • dry air • exposure • methacholine • organic dust

This article has been cited by other articles:

				A. Ek, L. Palmberg, B.-M. Sundblad, and K. Larsson Salmeterol Does Not Alter Increased Bronchial Responsiveness Caused by Organic Dust Exposure Chest, October 1, 2005; 128(4): 3038 - 3047. [Abstract] [Full Text] [PDF]

				A. Ek, L. Palmberg, and K. Larsson The effect of fluticasone on the airway inflammatory response to organic dust Eur. Respir. J., October 1, 2004; 24(4): 587 - 593. [Abstract] [Full Text] [PDF]