Detection of Small Airway Dysfunction in Asymptomatic Smokers with Preserved Spirometry: The Value of the Impulse Oscillometry System

Abstract

Purpose Smoking-induced bronchiolitis with progressive small airway dysfunction (SAD) is a leading cause of chronic obstructive pulmonary disease. We investigated the value of using the impulse oscillometry system (IOS) to detect SAD in asymptomatic smokers with preserved spirometry. Patients and Methods We included 75 asymptomatic smokers (37 females, mean age 47±12 years, 26±17 pack/year) with preserved spirometry [forced expiratory volume at 1st second (FEV1)/forced vital capacity (FVC) ≥0.70 and normal FVC] and 34 never-smokers (19 females, mean age 42±15 years). Results In smokers, pack/years were significantly related to spirometry and IOS parameters (p < 0.05). The values of the fall in resistance from 5 Hz to 20 Hz (R5 – R20) were significantly and inversely related to the values of the ratio of forced expiratory volume in 3 and in 6 seconds (FEV 3 /FEV 6 ) (p < 0.05). In addition, the percentage of heavy smokers (≥30 pack/year) with R5 – R20 >0.07 kPa·s·L −1 , considered as IOS index of SAD, but not with FEV3/FEV6 less than a lower limit of normal, a spirometry index of SAD, was significantly higher than that of mild smokers (<30 pack/year) and never-smokers (p < 0.05). Conclusion This study demonstrates that IOS has the potential to detect SAD in asymptomatic heavy smokers with preserved spirometry and with FEV3/FEV6 values in the normal range. We confirm that IOS provides parameters which can complement traditional measurements of pulmonary function.

Impulse Oscillometry, Small Airways Disease, and Extra-Fine Formulations in Asthma and Chronic Obstructive Pulmonary Disease: Windows for New Opportunities

“… 2 Recent results from the one-year longitudinal arm of the study confirmed that SAD predicts asthma control and exacerbations; in detail: R5-R20, AX, X5 and FEV1 were significantly correlated with asthma control, while FEV1 and R5-R20 were significantly correlated with QoL. 12 …”

“…In particular, the progression of disease in terms of aggravation and worse control, have been found to be associated with residual volume/total lung capacity (RV/TLC) and R5-R20, 1 , 2 R5, X5, AX and FRES, 1 , 12 worse forced mid-expiratory flow (FEF25–75%), forced vital capacity (FVC), RV and higher FENO, exercise or allergic-induced asthma symptoms and asthma-related night awakenings ( Table 1 ). 1 , 2 , 12–15 …”

“…Ideally, it should also have a role in smoking cessation clinics as a motivational tool, showing the patient the underlying lung damage despite normal spirometry values (FEF 25–75% cannot be considered a reliable parameter). 12 So far, limits to the inclusion of the test in standard COPD management protocols are represented by the few resources for purchase and/or functioning of instrument; time of examination in relation to visit with pneumologist.…”

Small Airways: Not Just Air Ducts – Pathophysiological Aspects and Clinical Implications

“…The respiratory system reactance (X5) reflects inertance and elasticity or capacitance (including small peripheral airways) [27]. R5–R20 was found to be more sensitive than FEV 3 /FEV 6 in order to intercept peripheral airway dysfunction in asymptomatic smokers with preserved spirometry [6].…”

“…Given the surface area and number of small airways, injury must be extensive for the insult to manifest functionally. For example, it has been shown that asymptomatic heavy smokers with spirometry in the normal range may have small airway dysfunction [6]. Furthermore, in pulmonary emphysema, small airway injury precedes alveolar rupture, which is the most specific pathophysiological feature [7].…”