Chronic obstructive pulmonary disease (COPD)COPD is defined as 'a common, preventable and treatable disease that is characterized by persistent respiratory symptoms and airflow limitation that is due to airway and/or alveolar abnormalities usually caused by significant exposure to noxious particles or gases and influenced by host factors including abnormal lung development. Significant comorbidities may have an impact on morbidity and mortality'. 1 Worldwide, the prevalence of COPD was estimated by the Global Burden of Disease Study at 3.9% in 2017. 2 COPD is a major cause of burden and mortality. Annually, COPD accounts for 5.7% of all-cause deaths and 3.3% of all-cause disability-adjusted life years. 2 In the Netherlands, the prevalence was estimated at 3.4% in 2019, and about 7000 people died because of COPD. 3 Due to longevity and persistent exposure to COPD risk factors, prevalence and burden of COPD will continue to increase. 1 According to the World Health Organization (WHO), COPD will be the fourth leading cause of mortality and the seventh leading cause of disability-adjusted life years in 2030. 4 COPD is also associated with an increased economic and societal burden. COPD results in increased disability, leading to increased healthcare costs. Within the European Union, 6% of healthcare spending is accounted to direct costs of COPD. 5 Especially exacerbations and hospital admissions attribute to an increase in healthcare costs. [6][7][8][9] Most common symptoms in advanced COPD are breathlessness, fatigue, muscle weakness, cough and sputum production. 1,10 Presence of these symptoms has a major impact on quality of life and functional status. 11-13 A prospective survey among 100 patients with advanced COPD showed that impairment in quality of life was strongly associated with high symptom burden, disease-related dysfunction and impaired psychological wellbeing. 14 Furthermore, COPD is associated with a higher number of comorbidities than other diseases, 15 including cardiovascular, cachectic, metabolic and psychological comorbidities. 10,16 As was shown by a cross-sectional analysis of Scottish national data, half of patients with COPD aged over 65 has at least three other morbidities. 17 Management of COPD includes reduction of exposure to risk factors like smoking cessation, pharmacological treatment like inhaled bronchodilators or corticosteroids and nonpharmacological treatment like pulmonary rehabilitation. In patients who still experience symptoms despite optimal pharmacological and nonpharmacological management, palliative care is indicated. 1 12 Chapter 1 work/effort and air hunger, patients usually experience all clusters during an exacerbation. 34,35,[38][39][40] Assessing breathlessness Measurement of breathlessness serves different purposes. First, measures can be used to discriminate between patients with mild or severe breathlessness. Second, change of breathlessness over time can be measured, for instance to evaluate the effectiveness of an intervention. 41 Since breathlessness ...