Obstructive Lung Diseases: Airways 2 |

Identification of Phenotypes of COPD Using Respiratory Impedance FREE TO VIEW

Daniel Katzman, MD; Roberta Goldring, MD; Beno Oppenheimer, MD; Kenneth Berger, MD
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New York University, New York, NY

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

Chest. 2016;150(4_S):844A. doi:10.1016/j.chest.2016.08.944
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SESSION TYPE: Original Investigation Poster

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

PURPOSE: In patients with COPD, the severity of airflow limitation has previously been demonstrated to weakly correlate with impedance as assessed by forced oscillation technique (FOT). Since physiologic phenotypes of COPD encompass a mixture of airway disease (chronic bronchitis) and parenchymal disease (emphysema), we hypothesize that the variable contributions of these disease processes will determine the pattern of abnormality on FOT. The present study evaluates the role of FOT in distinguishing COPD phenotypes in patients characterized by standard pulmonary function tests, esophageal manometry, and imaging.

METHODS: Data was reviewed retrospectively of nine patients evaluated for COPD who underwent esophageal manometry for assessment of lung recoil based on elevated FRC. All patients had radiographic evidence of either bronchial wall thickening, emphysema, or both. Based on radiographic findings, patients were given a phenotype classification of emphysema predominant, chronic bronchitis predominant, or a mixed phenotype. Lung function testing by spirometry, plethysmography, diffusion, esophageal manometry, and FOT were performed by standard methods.

RESULTS: Eight of nine patients were male; age ranged from 47-68yr. Seven patients had a smoking history, and seven had a BMI<30kg/m2. Airflow obstruction (FEV1/FVC < 0.7) was present in eight of nine patients (range 0.28-0.81). All patients had an elevated FRC (range 113-184% predicted) and TLC was elevated in five patients (range 90-148% predicted). DLCO was reduced in seven of eight patients with valid data (range 28% to 117% predicted). Three patients were classified as emphysema predominant, three chronic bronchitis predominant, and three with a mixed phenotype. Lung recoil pressure was reduced in all patients with emphysema predominant (range 9-20cmH2O), in two of three patients with a mixed phenotype (range 9-27cmH2O), and in one of three patients with chronic bronchitis predominant (range 14-25cmH2O). Oscillometry testing revealed normal to near normal resistance and reactance in the emphysema predominant phenotype (R5, 3.12-5.94cmH2O/l/s; R5-20, 0.39-1.24cmH2O/l/s; X5, -0.11- -1.11cmH2O/l/s). Resistance and reactance were elevated in chronic bronchitis predominant and mixed phenotypes (R5, 6.59-11.47cmH2O/l/s; R5-20, 2.16-3.80cmH2O/l/s; X5, -2.50- -6.59cmH2O/l/s).

CONCLUSIONS: Oscillometry parameters vary widely in patients with COPD and are dependent on the balance between chronic bronchitis and emphysema. In the three COPD patients with a emphysema predominant phenotype, there were minimal abnormalities by FOT despite significant abnormalities by spirometry. This phenotype appears to be distinguishable from a chronic bronchitis predominant phenotype and from a mixed chronic bronchitis and emphysema phenotype by FOT despite similar degrees of airflow limitation.

CLINICAL IMPLICATIONS: Therapeutic approach to patients with COPD may depend on the variable contributions of emphysema and chronic bronchitis. FOT appears to have a role in distinguishing an emphysema predominant phenotype from a chronic bronchitis predominant and mixed phenotypes.

DISCLOSURE: The following authors have nothing to disclose: Daniel Katzman, Roberta Goldring, Beno Oppenheimer, Kenneth Berger

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