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Airway Injury in Swine Confinement Workers

David A. Schwartz, MD, MPH; Steve K. Landas, MD; Deborah L. Lassise, MS; Leon F. Burmeister, PhD; Gary W. Hunninghake, MD; and James A. Merchant, MD, DrPH
[+] Article, Author, and Disclosure Information

Grant Support: By a National Heart, Lung, and Blood Institute SCOR grant HL-37121, a Merit Review award from the Department of Veterans Affairs, and grant OH-00093 from the National Institute of Occupational Safety and Health Centers for Disease Control. Dr. Schwartz is a recipient of a Clinical Investigational Award (ES-00203) from the National Institute of Environmental Health Sciences.

Requests for Reprints: David A. Schwartz, MD, MPH, Pulmonary Disease Division, Department of Internal Medicine, The University of Iowa College of Medicine, Iowa City, IA 52242.

Current Author Addresses: Drs. Schwartz, Landas, and Hunninghake: University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242.

Ms. Lassise: 4 Hampshire Court, Mason City, IA 50401.

Dr. Burmeister: 2825 Stendler Building, University of Iowa, Iowa City, IA 52242.

Dr. Merchant: 126 AMRF, Oakdale, University of Iowa, Oakdale, IA 52319.

Ann Intern Med. 1992;116(8):630-635. doi:10.7326/0003-4819-116-8-630
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Objective: To determine whether work-related respiratory symptoms are indicative of underlying lung disease among swine confinement workers and, if so, to identify whether respiratory changes were more indicative of airway or of interstitial lung injury.

Design: Nested case-control study within a population-based longitudinal study.

Setting: University hospital.

Participants: Study participants were randomly selected from a group of 207 swine confinement workers followed longitudinally. Of these, 43 workers with respiratory symptoms were identified, and 31 were randomly selected for inclusion in this study. Three control groups (swine confinement workers, neighbor farmers, and blue collar workers) without work-related respiratory symptoms were frequency-matched by age, sex, and smoking status to the symptomatic swine confinement workers.

Measurements: Spirometry and lung volumes, diffusing capacity of carbon monoxide, chest radiograph, methacholine airway challenge, and bronchoalveolar lavage were done. An endobronchial biopsy was done in the last 27 participants evaluated.

Results: Although Spirometric measures of airflow were similar between the symptomatic swine confinement workers and the three control groups, swine confinement cases were found to have significant elevations in residual volume (126.5 ±28.2 L) when compared to swine confinement controls (115.4 ±38.4 L; P≤ 0.05), neighborhood farmer controls (101.1 ± 29.4 L; P≤ 0.005), and blue collar controls (106.4 ± 30.4 L; P ≤ 0.05). Swine confinement cases also had an enhanced airway response to inhaled methacholine and had thickening of the epithelial basement membrane of the lobar bronchi. No parenchymal injury was observed in the swine confinement cases.

Conclusions: Our findings suggest that swine confinement workers who have work-related respiratory symptoms are at risk for airway, but not parenchymal, lung injury, and that spirometry may not accurately reflect the extent of airway injury.





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