I. Introduction
Chronic Obstructive Pulmonary Disease (COPD) is a common preventable and treatable disease characterized by persistent airflow limitations, slowly progressive, partially or totally irreversible, and associated with an enhanced chronic inflammatory response to noxious particles or gases in the airways and in the lung [1]. As the disease progresses, the patients lose efficiency of respiratory muscles and the airways undergo progressive obstruction. COPD is currently a major cause of chronic morbidity and mortality throughout the world and it is predicted to become the main one by 2020 [2]. Patients affected by COPD also suffer from periodic worsening of symptoms and lung function lasting for several days, such as exacerbations, tachycardia, dyspnoea and hypoxemia [3]. Although early intervention with antibiotics and steroids can prevent COPD-related hospital admissions, several patients are not able to promptly recognize early signs and symptoms of these worrisome events from day-to-day variations. These events induce deteriorations in respiratory health and aggravate the course of the disease, resulting in larger use of healthcare services and lower health-related quality of life (HRQoL) [4].