Comparative Airway Response to High- vs 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, Québec, Québec, Canada
² Service de pneumologie, Hôpital du Sacré-Cur, Université de, Montréal, Montréal, Québec, Canada

^* To whom correspondence should be addressed. E-mail: lpboulet{at}med.ulaval.ca.

	Abstract

Airway responses to occupational agents in sensitized workers may vary, clinically and physiologically. We compared 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 in sensitized workers.

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

Maximum falls in FEV₁ were of similar magnitude for both types of agents. Compared with high molecular weight agents, low molecular weight substances induced more frequently late or dual responses and higher increases in airway responsiveness. After exposure to high molecular weight agents, there was a mean reduction in doubling concentrations of methacholine (±SD) of 0.5±1.7 for early responses, compared to 2.8±1.2 for late responses, and 1.4±2.0 for dual responses. Isolated early responses were more frequently found in women, smokers, workers with a higher % predicted FEV₁ and higher PC₂₀, and in those with longer asthma duration.

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