Sputum Induction and Bronchoscopy for Assessment of Ozone-Induced Airway Inflammation in Asthma Outcomes

Spirometry

The mean (± SD) values of the spirometry indexes are shown in Table 2. The preexposure FEVj values for all subjects were similar in all arms of the study. Across FA exposures, there was a slight increase in FEV1. Across O3 exposures, there was a significant decrease in FEV1. The post-FA exposure FEV1 values for all subjects were similar in the SI and bronchoscopy arms of the study, as they were after O3. FVC and maximal mid-expiratory flow rate followed a pattern of change that was similar to that of FEVr

O3-Induced Neutrophilia in Induced Sputum, BFx Fluid, and BAL Fluid

In comparison with FA exposure, O3 exposure significantly increased the %PMNs in induced sputum (mean increase in the %PMNs, 10.1%; 95% confidence interval [CI], 0.2 to 20.0), BFx fluid (mean increase in %PMNs, 17.0%; 95% CI, 8.8 to 25.3), and BAL fluid (mean increase in %PMNs, 7.5%; 95% CI, 2.3 to 12.6) [Table 3]. The O3-induced increases in %PMNs in BFx and BAL fluid were associated with much smaller p values than those in induced sputum because of the smaller variation associated with %PMNs in BFx and BAL samples. O3 exposure also increased the concentration of neutrophils in induced sputum, BFx fluid, and BAL fluid, but the increase in sputum was not statistically significant (p = 0.149).
BAL fluid

Correlation of Induced Sputum Data With Lavage Data

To determine how well the inflammatory indexes in induced sputum correlated with those in BFx and BAL fluid, we constructed linear regression models of %PMNs in BFx and BAL fluid vs that in induced sputum, with induced sputum values as the independent variables and BFx and BAL values as the dependent variables (Fig 1). These regression models showed that the changes in %PMNs in sputum samples were not well-correlated with those in BFx and BAL fluid samples (BFx sample, R = 0.50; and BAL fluid sample, R = 0.12). We subsequently used this model to estimate the change in the %PMNs of BFx and BAL fluid samples from that in induced sputum samples, and then compared these estimated values with the actual measured values of BFx and BAL fluid samples. The differences between the estimated and measured values of BFx and BAL fluid samples were then considered as the estimate errors. The estimate error values were then compared with the actual measured changes (ie, the actual O3 effects) in the %PMNs in BFx and BAL (Table 4). The comparison showed that the estimate errors were similar to the actual measured changes in the %PMNs with a substantial overlap between their 95% CIs, making these estimates quite inaccurate (Fig 2).

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Linear regressions
Figure 1. Linear regressions of changes in the %PMNs in BFx and BAL fluid samples vs those in induced sputum (IS) samples. • = actual values of change in %PMNs in BFx and BAL fluid samples; D = predicted values of %PMNs for BFx and BAL fluid samples.

BAL fluid samples
Figure 2. The measured change in the %PMNs after O3 exposure in BFx and BAL fluid samples, and the errors in their estimates using the linear regression model based on induced sputum values. • = mean value of the change or the mean value of the error in the %PMNs in respiratory samples; bars = the corresponding 95% CIs.

Table 2—Spirometry Indices Before and After Each Exposure Arm

SpirometryIndices FA O3
SI BRX SI BRX
FVC, L
Before 4.0 ± 1.0 4.0 ± 1.2 4.1 ± 1.0 4.0 ± 1.0
After 4.0 ± 1.0 4.1 ± 1.0 3.5 ± 0.9 3.7 ± 0.9
FEVb L
Before 3.1 ± 1.1 3.2 ± 1.1 3.3 ± 0.9 3.1 ± 1.0
After 3.3 ± 0.9 3.4 ± 0.9 2.7 ± 0.8 2.8 ± 0.7
FEF25-75, LBefore 3.2 ± 1.8 3.3 ± 1.8 3.5 ± 1.5 3.2 ± 1.8
After 3.4 ± 1.6 3.6 ± 1.7 2.6 ± 1.6 2.7 ± 1.3

Table 3—Leukocyte and Neutrophil Counts in RTLF Samples

Sampling Method WBC, X104 cells/mL PMN,X 104 cells/mL %PMNs
IS
FA 49.4 ± 31.4 29.6 ± 27.9 51.3 ± 25.9
O3 75.6 ± 65.8 48.4 ± 43.0 61.4 ± 16.4i
BFx
FA 15.3 ± 8.7 1.01 ± 2.2 6.6 ± 11.9
O3 22.0 ± 11.8 .1 . 2 1 .
BAL
FA 15.8 ± 10.5 0.5 ± 0.3 3.3 ± 1.2
O3 19.6 ± 9.3 1.7 ± 0.9| 10.7 ± 8.0f
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Table 4—The Errors in Estimating the Effect of Ozone on the %PMNs in BAL Fluid or BFx Fluid From the Corresponding Changes in Induced Sputum

SamplingMethod Actual D in %PMN After O3 R2Valuef Absolute Error of D in %PMNs Using IS as Predictor
IS 10.1 (0.2-20.0)
BFx 17.0 (8.8-25.3) 0.247 9.7 (5.9-13.5)
BAL 7.5 (2.3-12.6) 0.013 5.5 (1.8-9.2)