Airway responses to the inhalation of cotton dust and cotton bract extracts

Background: Exposure to dust in the cotton industry is associated with respiratory dysfunction. Healthy subjects challenged with cotton bract extract (CBE) develop transient airway hyperresponsiveness. CBE, a major component of cotton dust, is potentially an important agent for studying byssinosis. Objectives: To compare airway responses to cotton dust extract (CDE) and CBE in healthy subjects. Methods: In 21 healthy, non-smoking subjects we compared the effects of CBE and CDE in a double-blind random order, following a 10-min aerosol inhalation. The response to methacholine (MCh) 2 h following CBE or CDE was measured. Lung function was recorded using maximal (MEFV) and partial expiratory flow volume (PEFV) curves, measuring MEF at 60% of baseline vital capacity below total lung capacity [MEF_40%(P)] on the PEFV curve. Responders were subjects who developed a 20% or greater fall in MEF _40%(P) following extract challenge. Endotoxin levels were low for CBE (5.71 EU/mg) and CDE (31.88 EU/mg). Results: There were 18 responders to CBE and 17 responders to CDE. The average maximal falls in MEF_40%(P) were 70 ± 4.9 and 70 ± 4.4% of baseline (nonsignificant) following CBE and CDE, respectively. All subjects enhanced their MCh response following CBE or CDE. The MCh dose which reduced MEF_40%(P) by 40% was identical for CBE and CDE (1.3 μg/ml). Conclusions: We conclude that CBE and CDE exert similar physiologic effects.