146 6 Chapter 6 Background Description of the condition Chronic obstructive pulmonary disease (COPD) is a heterogeneous, systemic condition characterised by restricted air ow that is not fully reversible. It is a major cause of morbidity because people with COPD experience chronic and progressive respiratory symptoms (i.e. dyspnoea and coughing) (GOLD 2020). The prevalence of COPD is currently estimated at 11.7% and is expected to increase substantially in the coming decades due to ageing of the world’s population, continued use of tobacco, and exposure to indoor biomass pollution (GOLD 2020; Lopez 2006; Lozano 2012). According to the World Health Organization (WHO), COPD is the fourth leading cause of death in the world (Lopez 2006; WHO 2020). Additionally, COPD has important nancial consequences, with high reported direct costs (e.g. healthcare resources, medication prescriptions) and indirect costs (e.g. absence from paid work, consequences of disability) (Britton 2003; FIRS 2017; Guarascio 2013). Optimal management of COPD is complex as it is a multi-component disease. Clinical, functional, and radiological presentations vary greatly from patient to patient, although patients may have a similar degree of air ow limitation (Agusti 2010; GOLD 2009; GOLD 2020; Wedzicha 2000). Previously, the sole focus in disease management lay on the degree of air ow limitation as a measure of disease severity (in the 2007 Global initiative for Chronic Obstructive Lung Disease (GOLD) classi cation of disease severity). This turned out to be a poor predictor of other important negative features of COPD, including health-related quality of life (HRQoL) and exercise tolerance (Agusti 2010; Burgel 2010). These patient-oriented outcomes are more important for people with COPD, given that COPD has a profound impact on HRQoL and exercise tolerance, even among those with modest air ow limitation (Engstrom 1996). Furthermore, impaired HRQoL (as shown in Domingo-Salvany 2002 , Fan 2002 , and Martinez 2006) and exercise tolerance (as reported in Gerardi 1996 and Pinto-Plata 2004) are associated with mortality (Cote 2009). Some people are more prone than others to episodes of acute exacerbation, which is an important additional cause of morbidity, mortality, hospital admission, and impaired health status (Calverley 2003; Seemungal 1998; Wedzicha 2000). Although exacerbations become more severe and occur more frequently with increased severity of COPD, this is not always the case. There is evidence for a ‘frequentexacerbation’ phenotype (or group of people) with exacerbation more often than would be expected given disease ‘severity’ as predicted by lung function testing (Hurst 2010; Le Rouzic 2018). Description of the intervention Given that COPD is a disease with a clinically heterogeneous picture characterised by multiple disease components, treatment of patients with COPD requires that these di erent components of the disease be addressed in a comprehensive programme known as integrated disease management (IDM).
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