Obstructive Lung Diseases: Airways 2 |

Impulse Oscillometry Distribution of Airway Resistance Correlates With Severity of Lung Disease FREE TO VIEW

Yewande Odeyemi, MD; Peter Whitesell, MD
Author and Funding Information

Howard University Hospital, Washington, DC

Copyright 2016, American College of Chest Physicians. All Rights Reserved.

Chest. 2016;150(4_S):836A. doi:10.1016/j.chest.2016.08.936
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SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 26, 2016 at 01:30 PM - 02:30 PM

PURPOSE: Increasing evidence indicates that inflammation of peripheral airways plays an important role in the pathophysiology of obstructive lung disease and may correlate more closely with severity of dyspnea than spirometric parameters. Impulse Oscillometry (IOS) is a well validated and effort-independent tool which allows for distinguishing proximal airway resistance (R20) from total airway resistance (R5). Limited data are available regarding the relative contribution of the small airways to overall resistance in patients with different pathophysiology and severity of disease. We hypothesized that sites of resistance as demonstrated with IOS would vary with different patterns of impairment and severity of disease.

METHODS: Consecutive patients referred for pulmonary function testing were asked to perform impulse oscillometry assessment at the same visit. Participants were categorized into 4 major groups by spirometry using the ATS/ERS Criteria, namely: Obstructive (FEV1/FVC <LLN), Restrictive (FEV1/FVC >LLN and FVC < 80% predicted), Mixed, and Normal. The forced expiratory volume in the first second (FEV1) was used to assess severity of lung disease and distal airway resistance (R5-R20) was calculated by subtracting the proximal airway resistance (R20) from the total airway resistance (R5). The percentage of distal airway resistance to total resistance was calculated as R5-R20/R5 * 100.

RESULTS: The analytic sample included a total of 47 participants. Of these 68% were women and 97% Caucasians. The mean age of the participants was 66 ± 4.2, and BMI mean 30.3 ±6.9. The % predicted FEV1 was 83% ± 30%, and mean FVC was 85 ± 23%. There were 9 obstructive patients, 5 mixed, 11 restrictive, and 22 normals. Mean R5-R20/R5% was 31 % overall, 36% in obstructive patients, 34% in restrictives, 47% in mixed and 26% in normal. Values did not correlate with pack-year smoking history. On Bivariate analysis, R5-R20 was negatively correlated with % predicted FEV1 in the total population (R2 = 0.518), normal (R2 = 0.58), mixed (R2 = 0.58) with a stronger correlation noted in the obstructive group ( R2 = 0.80) with no correlation noted in the restrictive group (R2 = 0.0). Correlation was also seen between R5-R20/R5% and % predicted FEV1 in the total population, normal group, mixed and the obstructive group (R2: 0.5, 0.3, 0.6 and 0.75 respectively).

CONCLUSIONS: This small pilot study suggests that distal airway resistance accounts for a higher percentage of total airway resistance in obstructive lung diseases as compared with other diseases and that it represents an increasingly higher percentage of total resistance with increasing disease severity. Larger prospective studies with are needed to confirm this finding and to evaluate small airway resistance correlation with specific phenotypes of obstruction and clinical symptoms

CLINICAL IMPLICATIONS: Impulse Oscillometry might be a better tool in monitoring severityand response to treatment in obstructive lung disease.

DISCLOSURE: The following authors have nothing to disclose: Yewande Odeyemi, Peter Whitesell

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