Airway inflammation in COPD: physiological outcome measures and induced sputum

Abstract

Chronic obstructive pulmonary disease (COPD) is a result of airway inflammation, and the best predictor of COPD is the early detection of airflow limitation by spirometry. The Global Initiative for Obstructive Lung Disease Workshop Report defines airflow limitation using simple spirometric indices. Available guidelines categorise the severity of COPD using forced expiratory volume in one second (FEV1) and forced vital capacity (FVC), with symptoms playing a minor role in the assessment.Current standards define COPD by progressive loss of FEV1, and thus longitudinal decline in FEV1 will be the primary outcome variable for intervention studies aimed at preventing or reducing the loss of pulmonary function. There is evidence, however, that the variable FEV1/FVC and FEV1 are often not measured properly in all settings.This article will discuss the roles of physiological measurements in diagnosing COPD and physiological outcome measures for COPD. It does not formally compare physiological measures with other outcome measures, such as symptoms or quality of life. Additionally, improved treatment of established disease requires a better understanding of the inflammatory process and its clinical effects and treatment.The inflammatory process, and how drugs affect it, can be studied noninvasively or relatively noninvasively by using refined methods of examining spontaneous or induced sputum. Enhanced understanding of the use of induced sputum will assist in predicting patients9 responses to short-and long-term inhaled corticosteroid treatment, and the methods of sputum examination need to be simplified so that they can be applied more easily to clinical practice. Eur Respir J 2003; 21: Suppl. 41, 19s- Chronic obstructive pulmonary disease (COPD) is defined by the Global Initiative for Obstructive Lung Disease (GOLD) as a "disease state characterised by airflow limitation that is not fully reversible. …The airflow limitation is usually both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases" [1]. The absence of reversibility tends to exclude asthma by definition, although asthma can coexist with COPD. Methods of assessing airflow limitation: current recommendations and their limitationsAvailable guidelines categorise the severity of COPD primarily by using forced expiratory volume in one second (FEV1), whereas symptoms play a minor role in the assessment [1][2][3][4][5]. This tight link between FEV1 and COPD reflects the fact that spirometry is the standard for defining the presence of airway obstruction and the progressive loss of FEV1, the physiological variable that characterises COPD severity and predicts its mortality. Spirometry has become the standard, in part, because good quality and inexpensive tests are widely available.The GOLD Workshop Report explicitly defines airflow limitation using simple spirometric indices. Specifically, airflow limitation is defined as an FEV1/forced vital capacity (FVC)v70% and a postbronchodilator FEV1v80% of predict...

Airflow pattern complexity and airway obstruction in asthma

“…Accordingly, these measurements may be unreliable and variable if suboptimal maneuvers are performed (26). Moreover, some patients are not able to reliably perform spirometry because it requires good subject cooperation and maximal effort (7). It was also observed that spirometric exams can lead to temporary alteration in bronchomotor tone due to the deep inspiration required, which can have implications for respiratory mechanics measurements (26).…”

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

“…However, the modifications to respiratory mechanics are not always detected by this test (Coe et al 1989). Moreover, some patients are not able to reliably perform spirometry, as the methods require good subject co-operation and maximal effort (Crapo et al, 2003). Whole-body plethysmography features a more complex method in which the individual must remain isolated from the external environment, breathing spontaneously within a hermetically sealed box (ATS/ERS, 2005).…”

“…Recommendations for research in COPD (Croxton et al, 2002) include the need for improved noninvasive mechanical tests of lung function. In this context, FOT was suggested by Crapo et al (2003) as an attractive alternative for diagnosing obstruction in COPD, as it requires little patient effort and cooperation. A brief description of this technique is provided in the next section.…”

Biomarkers in COPD

“…Sputum induction is a practical and safe procedure and an important research tool of local inflammation in the lung [4]. Recently, a significant body of data has accumulated regarding differences in sputum characteristics between COPD patients and healthy smokers, which could serve as markers for COPD susceptibility [9][10]. Inflammatory cell populations and subpopulations in sputum cellular phase can be easily studied using chemical and immunocytochemical methods.…”