Obstructive Lung Diseases: Airways 1 |

Role of Lung Volumes, Airway Resistance and Diffusion in Differentiating Asthma With Incomplete Reversibility (AIR) From COPD FREE TO VIEW

Isha Garg, MD; K C Agarwal, MD; Gopal Purohit, MD; C R Choudhary, MD; Srikant Agarwal, MD
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Dr S.N. Medical College, Panipat, India

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

Chest. 2016;150(4_S):830A. doi:10.1016/j.chest.2016.08.930
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SESSION TYPE: Original Investigation Poster

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

PURPOSE: To explore various pulmonary function parameters that can help to differentiate AIR from COPD patients with similar degree of obstruction.

METHODS: Total 101 patients, 51 Asthma (35 Males & 16 Females) and 50 COPD (48 Males & 2 Females) already on treatment, subjected to extensive lung function tests including pre and post bronchodilator spirometry, Body plethysmography and Diffusion capacity with carbon monoxide(DLCO).They were stratified into 4 groups according to severity of obstruction (FEV1%) ie. ≥ 80%, 51-79%, 31-50% and ≤ 30%.Both the groups were compared for FRC% (Functional Residual Capacity), TLC% (Total Lung Capacity), RV% (Residual Volume), RV/TLC%, Raw (airway resistance), sGaw (specific airway conductance) with postbronchodilator reversibility and DLCO% using independent t-test. Correlation of FEV1% with other parameters was done using Pearson analysis.

RESULTS: The mean age of COPD and AIR patients was 61.14 ± 9.37 and 49.25 ± 7.92 years with smoking history of 37.2 and 1.4 pack years respectively.With similar degree of FEV1% severity, DLCO%, sGaw% ,post bronchodilator reversibility of Raw as well as sGaw were found highly significant in differentiating the two groups. Pearson correlation revealed significant negative association of FEV1% with FRC%, RV%, RV/TLC%, pre bronchodilator Raw% and positive correlation of pre bronchodilator sGaw% amongst both AIR and COPD patients. Additionally, DLCO% was significantly positively associated with FEV1% in COPD patients (p=0.002).

CONCLUSIONS: Post bronchodilator reversibility of Airway resistance (Raw) and Conductance (sGaw) along with DLCO may help to differentiate AIR from COPD. Findings of higher bronchodilator response in airway resistance and conductance with relatively preserved DLCO favours Asthma patients.

CLINICAL IMPLICATIONS: Asthma and COPD, both characterised by airflow obstruction, may be difficult to differentiate in clinical practice especially when Asthma presents with a component of incomplete reversibility.Distinction is essential as both warrants different line of management.Extensive Pulmonary Functions work-up including pre and post bronchodilator Body plethysmography and Diffusion studies may help in their differentiation.

DISCLOSURE: The following authors have nothing to disclose: Isha Garg, K C Agarwal, Gopal Purohit, C R Choudhary, Srikant Agarwal

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