Chest
Volume 144, Issue 1, July 2013, Pages 249-257
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Original Research
Occupational and Environmental Lung Diseases
Lessons From the World Trade Center Disaster: Airway Disease Presenting as Restrictive Dysfunction

https://doi.org/10.1378/chest.12-1411Get rights and content

Background

The present study (1) characterizes a physiologic phenotype of restrictive dysfunction due to airway injury and (2) compares this phenotype to the phenotype of interstitial lung disease (ILD).

Methods

This is a retrospective study of 54 persistently symptomatic subjects following World Trade Center (WTC) dust exposure. Inclusion criteria were reduced vital capacity (VC), FEV1/VC > 77%, and normal chest roentgenogram. Measurements included spirometry, plethysmography, diffusing capacity of lung for carbon monoxide (Dlco), impulse oscillometry (IOS), inspiratory/expiratory CT scan, and lung compliance (n = 16).

Results

VC was reduced (46% to 83% predicted) because of the reduction of expiratory reserve volume (43% ± 26% predicted) with preservation of inspiratory capacity (IC) (85% ± 16% predicted). Total lung capacity (TLC) was reduced, confirming restriction (73% ± 8% predicted); however, elevated residual volume to TLC ratio (0.35 ± 0.08) suggested air trapping (AT). Dlco was reduced (78% ± 15% predicted) with elevated Dlco/alveolar volume (5.3 ± 0.8 [mL/mm Hg/min]/L). IOS demonstrated abnormalities in resistance and/or reactance in 50 of 54 subjects. CT scan demonstrated bronchial wall thickening and/or AT in 40 of 54 subjects; parenchymal disease was not evident in any subject. Specific compliance at functional residual capacity (FRC) (0.07 ± 0.02 [L/cm H2O]/L) and recoil pressure (Pel) at TLC (27 ± 7 cm H2O) were normal. In contrast to patients with ILD, lung expansion was not limited, since IC, Pel, and inspiratory muscle pressure were normal. Reduced TLC was attributable to reduced FRC, compatible with airway closure in the tidal range.

Conclusions

This study describes a distinct physiologic phenotype of restriction due to airway dysfunction. This pattern was observed following WTC dust exposure, has been reported in other clinical settings (eg, asthma), and should be incorporated into the definition of restrictive dysfunction.

Section snippets

Materials and Methods

This study retrospectively analyzed data from 54 subjects with persistent respiratory symptoms and unexplained reduction in VC. Inclusion criteria were as follows: (1) exposure to WTC dust, (2) reduction in VC below the lower limit of normal (LLN) on initial screening spirometry,14 (3) FEV1/VC ≥ 77% (mean ± SD, 82% ± 5%) (this value exceeds the LLN of commonly used predicted equations and ensures that subjects with mild large airway disease were excluded15), and (4) absence of parenchymal,

Results

Table 1 illustrates clinical characteristics of the patients. Mean age was 47 ± 10 years. Potential causes for airway dysfunction included current/prior cigarette smoking in 39% of subjects, history of asthma in 15%, and obesity in 49%. Approximately one-half the cohort reported dust cloud exposure. Predominant symptoms were cough and exertional dyspnea. By design, FEV1/VC was ≥ 77% in all subjects. The expiratory flow rate measured at 50% of VC was normal (expressed relative to VC) in all

Discussion

This study demonstrates a distinct physiologic phenotype that differs from classic obstructive and restrictive patterns. The abnormality resembled a restrictive defect, with reduced VC, FRC, and TLC and preservation of FEV1/VC, but parenchymal, chest wall, or neuromuscular disease were not present. Plethysmography demonstrated AT, oscillometry demonstrated abnormalities responsive to bronchodilator, and although Dlco was variably reduced, Dlco/Va was normal or elevated in all subjects. Thus,

Acknowledgments

Author contributions: Dr Berger had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Dr Berger: contributed to study design, data interpretation, and writing of the manuscript.

Dr Reibman: contributed to referring patients for evaluation, provided clinical and imaging data, and contributed to data interpretation and writing of the manuscript.

Dr Oppenheimer: contributed to study design, data interpretation,

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    Funding/Support: This work was supported by the Centers for Disease Control and Prevention [Grants 200-2011-39413, 200-2011-39391, and 200-2011-39397], the National Institute for Occupational Safety and Health [Grant 5E11OH009630], and the American Red Cross Liberty Disaster Relief Fund, City of New York.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

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