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Comparative airway response to high- versus low-molecular weight agents in occupational asthma

¹ Unité de recherche en pneumologie, Centre de recherche de l'Hôpital Laval, Institut Universitaire de cardiologie et de pneumologie, Hôpital Laval, , Quebec, and ² Service de pneumologie, Hôpital du Sacré-Cœur, Université de Montréal, Montreal, QC, Canada.

CORRESPONDENCE: L-P. Boulet, Hôpital Laval, 2725 Chemin Sainte-Foy, Quebec, Canada G1V 4G5. Fax: 1 4186564762. E-mail: lpboulet{at}med.ulaval.ca

Keywords: Airway inflammation, airway responsiveness, occupational asthma, specific inhalation challenge

Received: September 11, 2007
Accepted December 8, 2008

Airway responses to occupational agents in sensitised workers may vary clinically and physiologically. The patterns of change in airway responsiveness, type of response and fall in expiratory flows following laboratory exposure to high- or low-molecular weight agents (HMW and LMW agents, respectively) were compared in sensitised workers.

Data on workers who underwent specific inhalation challenges with occupational sensitisers (117 exposed to HMW agents and 130 to LMW agents) were collected from their medical charts.

Maximum falls in forced expiratory volume in one second (FEV₁) were of similar magnitude for both types of agents. Compared with HMW agents, LMW agents induced more frequently late or dual responses and higher increases in airway responsiveness. After exposure to HMW agents, there was a mean±SD reduction in doubling concentrations of methacholine of 0.5±1.7 for early responses, compared with 2.8±1.2 and 1.4±2.0 for late and dual responses, respectively. Isolated early responses were more frequently found in females, smokers, workers with a higher % predicted FEV₁ and higher provocation concentration causing a 20% fall in FEV₁, and in those with longer asthma duration.

Workers’ characteristics, as well as the type of agent they are sensitised to, may help to predict the type of response after specific inhalation challenge.