**4. Chronic obstructive pulmonary disease**

COPD is a preventable and treatable disease characterized by partially reversible airflow limitation [27, 28]. The limitation is often progressive and is associated with an abnormal inflammatory response of the lungs to noxious particles or gases, especially cigarette smoke [27]. COPD increases mortality in worldwide each year, causing socio-economic damage. The total deaths from COPD are projected to increase by 30% over the next 10 years, unless urgent measures are taken to reduce the risk factors, particularly tobacco use. Estimates indicate that by 2030, COPD may become the third leading cause of death [6].

The COPD is characterized by the presence of chronic bronchitis, obstructive bronchiolitis and emphysema [27, 28]. Chronic bronchitis is inflammation of the airways which deliver air to the lungs. This can lead to an increase in mucus production and consequent narrowing of the bronchi (Figure 3). In emphysema, the tissue that surrounds the smaller airways is damaged and air becomes trapped in the alveoli. These air sacs become overstretched and unable to function correctly causing shortness of breath. The disease process is directly related to an inflammatory response of the lungs, triggering the destruction of the lung parenchyma. Such changes are responsible for airflow limitation and air trapping. [27]. Pathological changes occur in four different regions of the lung: the larger calibre airway, the peripheral airways, the lung parenchyma and the pulmonary vasculature [27-29]. In the larger calibre airways, structural changes occur in the goblet cells and submucosal glands causing mucus hyperse‐ cretion and squamous metaplasia, as shown in Figure 3 [27-29].

In the peripheral airways (<2 mm diameter), we observed thickening of the airway wall, peribronchial fibrosis, exudate, narrowing of the airways (obstructive bronchiolitis) and increased inflammatory response. In the lung parenchyma, the structural changes involved destruction of the alveolar wall, apoptosis of epithelial cells and emphysema [27-29]. The main characteristic of COPD is airflow obstruction, which is not fully reversible. Spirometry is the gold standard technique used to assess this obstruction [28, 29].

**Figure 3.** On the left, the effect of chronic bronchitis in which the inflammation of the airways can lead to an increase in mucus production and consequent narrowing of the bronchi. In emphysema (right), the tissue that surrounds the smaller airways is damaged and air becomes trapped in the alveoli. These air sacs become overstretched and unable to function correctly causing shortness of breath. (Source: http://www.livingwellwithcopd.com/en/what-is-copd.html).

The coordination between breathing andswallowing can be severelydisruptedinpatients with COPD due to their reduced ventilatory capacity. COPD also has the potential to disrupt the coordination of breathing and swallowing because of tachypnoea, an increased tendency to swallow during inspiration, reduced duration of apnea and changes in the mechanics of swallowing. The increase in the elastic and resistive respiratory loads, typical of these pa‐ tients, is associated with a rapid shallow pattern of breathing that may increase the risk of aspiration [8].
