Chest
Volume 132, Issue 4, October 2007, Pages 1275-1282
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ORIGINAL RESEARCH
ENVIRONMENTAL HEALTH
Distal Airway Function in Symptomatic Subjects With Normal Spirometry Following World Trade Center Dust Exposure

https://doi.org/10.1378/chest.07-0913Get rights and content

Rationale

Following collapse of the World Trade Center (WTC), individuals reported new-onset respiratory symptoms. Despite symptoms, spirometry often revealed normal airway function. However, bronchial wall thickening and air trapping were seen radiographically in some subjects. We hypothesized that symptomatic individuals following exposure to WTC dust may have functional abnormalities in distal airways not detectable with routine spirometry.

Methods

One hundred seventy-four subjects with respiratory symptoms and normal spirometry results were evaluated. Impedance oscillometry (IOS) was performed to determine resistance at 5 Hz, 5 to 20 Hz, and reactance area. Forty-three subjects were also tested for frequency dependence of compliance (FDC). Testing was repeated after bronchodilation.

Results

Predominant symptoms included cough (67%) and dyspnea (65%). Despite normal spirometry results, mean resistance at 5 Hz, 5 to 20 Hz, and reactance area were elevated (4.36 ± 0.12 cm H2O/L/s, 0.86 ± 0.05 cm H2O/L/s, and 6.12 ± 0.50 cm H2O/L, respectively) [mean ± SE]. Resistance and reactance normalized after bronchodilation. FDC was present in 37 of 43 individuals with improvement after bronchodilation.

Conclusions

Symptomatic individuals with presumed WTC dust/fume exposure and normal spirometry results displayed airway dysfunction based on the following: (1) elevated airway resistance and frequency dependence of resistance determined by IOS; (2) heterogeneity of distal airway function demonstrated by elevated reactance area on oscillometry and FDC; and (3) reversibility of these functional abnormalities to or toward normal following administration of a bronchodilator. Since spirometry results were normal in all subjects, these abnormalities likely reflect dysfunction in airways more distal to those evaluated by spirometry. Examination of distal airway function when spirometry results are normal may be important in the evaluation of subjects exposed to occupational and environmental hazards.

Clinical trials registration number

NCT00395330. http://www.clinicaltrials.gov.

Section snippets

Methods and Materials

Data from subjects referred to the New York University/Bellevue Hospital Pulmonary Function Laboratory for evaluation of respiratory symptoms following exposure to WTC dust were retrospectively analyzed. Subjects were referred from outpatient clinics including the Bellevue Hospital WTC Treatment Program. One hundred seventy-four subjects with normal spirometry results were included. Six exposure scenarios were defined: initial dust cloud, dust cleanup, involvement in rescue/recovery, residence

Results

Table 1 shows the demographic characteristics of the 174 subjects. Mean age was 44 ± 10 years. A history of asthma prior to September 11, 2001 was reported in 7%. Exposure to WTC dust varied and included exposure during cleanup activities (50%) or due to work or residence in the vicinity of the WTC (40%). All subjects were symptomatic; predominant symptoms included cough and dyspnea, and to a lesser extent wheezing and chest tightness.

Discussion

The present study investigated airway function in a cohort of subjects with new-onset respiratory symptoms after reported exposure to WTC dust/fumes in whom spirometry results were within normal limits. This cohort was specially selected because of reported exposure to WTC dust and were therefore potentially at risk for development of airway disease. Despite normal spirometry results, airway dysfunction was demonstrated based on the following: (1) elevated airway resistance and frequency

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    This work was done at New York University/Bellevue Medical Center, New York, NY.

    Support was provided by National Institute of Environmental Health Sciences grant ES00260, September 11 recovery grant from the American Red Cross Liberty Disaster Relief Fund, and National Center for Research Resources grant M01 RR-00096.

    The authors have no conflicts of interest to disclose.

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