The Relationship Between Airflow Obstruction, Emphysema Extent, and Small Airways Function in COPD

Assessing and accessing the small airways; implications for asthma management

“…In the late nineties, spirometric pattern characterized by a decrease in VC and FEV 1 , an increase in RV and RV/total lung capacity (TLC), and normal TLC and FEV 1 /FVC was described by Stanescu [28]. Since an increase in RV and RV/TLC represents a marker of hyperinflation and air trapping, this pattern has been proposed as an early detector of peripheral airways disease [29,30]. This alteration has been observed in the early stages of emphysema, elderly people and asymptomatic asthma [29,30].…”

“…Since an increase in RV and RV/TLC represents a marker of hyperinflation and air trapping, this pattern has been proposed as an early detector of peripheral airways disease [29,30]. This alteration has been observed in the early stages of emphysema, elderly people and asymptomatic asthma [29,30]. Although the measurement of RV is an easy-to-perform test, with good reproducibility and low intrapatient variability, it is commonly envisaged as a rough method of estimating the function of small airways, mainly because it only allows a volumetric characterization of premature airway closure and air trapping, and is not able to detect less evident functional changes of distal airways conductance and ventilation patterns.…”

Methods, Measurements, and Interpretation of Animal Lung Function in Health and Disease

“…After this region of the curve, there is usually a final increase in N 2 (phase IV), most notable in larger mammals, such as the dog (Mink et al, 1984) or human (Gold, 1982) where the size of the lung imposes a great hydrostatic gradient that more noticeably exhibits the impaired distal alveoli. The onset of phase IV, though often poorly defined on the rodent curve (Mauderly, 1989), is believed to signal progressive closure of more flaccid small airways, though this interpretation of added value as a measure of small airways dysfunction is debated, even in humans (Gold, 1982;Timmins et al, 2012). This volume difference from RV is the so-called closing volume, which should increase with obstructive airways diseases.…”

Forced Oscillation Technique in the Detection of Smoking-Induced Respiratory Changes

“…The role of FOT in the identification of "choke-points", where flow limitation occurs, was highlighted by Bates et al (2011). Timmins et al (2012) recently used single breath nitrogen washout and computerized tomography to study the relationship between airflow obstruction, emphysema extent and small-airways function in COPD. Single-frequency FOT (6 Hz) was also used to quantify EFL.…”