Isolated small airway reactivity during bronchoprovocation as a mechanism for respiratory symptoms in WTC dust-exposed community members.

Introduction: Small airway dysfunction occurs following WTC dust exposure, but its role in producing symptoms is unclear.

Methods: Methacholine challenge (MCT) was used to assess the relationship between onset of respiratory symptoms and small airway abnormalities in 166 symptomatic WTC dust-exposed patients. Forced oscillation testing (FOT) and respiratory symptoms were assessed during MCT. FOT parameters included resistance at 5 and 20 Hz (R5 and R20 ) and the R5 minus R20 (R5-20 ).

Results: Baseline spirometry was normal in all (mean FEV1 100 + 13% predicted, mean FEV1 /FVC 80 + 4%). MCT revealed bronchial hyperreactivity by spirometry in 67 patients. An additional 24 patients became symptomatic despite minimal FEV1 change (<5%); symptom onset coincided with increased R5 and R5-20 (P > 0.001 vs. baseline). The dose-response of FOT (reactivity) was greater compared with subjects that remained asymptomatic (P < 0.05).

Conclusions: FOT during MCT uncovered reactivity in small airways as a mechanism for respiratory symptoms in subjects with inhalational lung injury. Am. J. Ind. Med. 59:767-776, 2016. © 2016 Wiley Periodicals, Inc.