Respiratory tract inflammation in swine confinement workers studied using induced sputum and exhaled nitric oxide

Objective: To further define the asthma-like syndrome seen in swine confinement workers. Design: A crosssectional study was performed at a swine confinement facility in rural Nebraska and at the University of Nebraska Medical Center, Omaha, Nebraska. Participants: 24 swine confinement workers and 14 urban normal control subjects. All subjects completed a questionnaire concerning respiratory complaints. We performed hypertonic saline challenges on the swine confinement workers and control subjects in order to induce expectoration of sputum. Cell counts and cell differentials were determined in the induced sputum samples. Nasal, mean, and peak exhaled nitric oxide was measured in both groups. Spirometry was also done. Results: Swine confinement workers were significantly more likely to report wheezing, cough, and sinusitis symptoms than controls (p = .003). Macrophages were significantly elevated in the induced sputum samples of the swine confinement workers vs the control subjects (0.59 macrophages/mL ± 0.1 SEM vs 0.36 ± .16; p = .006), while there was no difference in numbers of neutrophils. No eosinophils were observed. A small elevation in mean exhaled nitric oxide was seen in the swine confinement workers compared to normal controls (11.7 ppb ± 0.6 SEM vs 10.2 ± 1.6; p = 0.023). Spirometry values did not differ statistically between swine confinement workers and the control group. Conclusions: Swine confinement workers have signs and symptoms of lower respiratory tract inflammation when studied using induced sputum and exhaled nitric oxide. Findings in the swine confinement workers differ from those in asthmatics and chronic bronchitis.