Nasal response in subjects undergoing challenges by inhaling occupational agents causing asthma through the nose and mouth.

Background: Subjects with occupational asthma (OA) often report nasal symptoms, but nasal reactions to inhalation challenges with occupational agents have not been well characterized.
Methods: Fifteen subjects with OA (eight due to high-molecular-weight agents--flour and guar gum--and seven due to isocyanates) underwent inhalational challenges using closed-circuit devices (dry particles for high-molecular-weight agents and gas generator for isocyanates) on two occasions, 2-4 weeks apart in a random fashion. On one occasion, they inhaled through the nose and, on another, through the mouth. The FEV1 was monitored for up to 8 h afterward, and symptoms were documented with a standardized questionnaire on nasal symptomatology, assessment of nasal resistance by rhinomanometry, and nasal lavage for the examination of cells and mediators.
Results: Inhaling through the mouth and through the nose: 1) yielded similar asthmatic responses (25+/-8% and 22+/-10% maximum changes in FEV1) 2) more than doubled the peak nasal symptoms and nasal resistance when the maximum daily response was compared with prechallenge results. This increase occurred on the days of inhalational challenges through the mouth and through the nose. There were some significant responses assessed by nasal lavage in terms of cells and mediators, again with no differences between the days of challenges through the mouth and through the nose.
Conclusions: Inhaling occupational agents of high or low molecular weight, including isocyanates, whether through the mouth or nose: 1) results in a similar asthmatic response 2) causes a significant nasal response in terms of symptoms and an increase in nasal resistance 3) causes some significant changes in inflammatory cells and mediators.