Pulmonary Dysfunction in COPD

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality all around the world. It has been identified as the fourth leading cause, which will rise globally to the third place, before the end of 2020. It is estimated that more than 12 million adults suffer from COPD in the USA and 24 million patients have an impaired lung function, which may lead to the development of COPD. Tobacco smoke is the predominant but not the only environmental risk factor for COPD. COPD is a burden for health providing systems as the estimated direct and indirect costs are constantly raising. Chronic obstructive pulmonary disease, namely, pulmonary emphysema and chronic bronchitis, is a chronic inflammatory response of the airways to noxious particles or gases, with resulting pathological and pathophysiological changes in the lung. The main pathophysiological aspects of the disease are airflow obstruction and hyperinflation, which are discussed by D. Papandrinopoulou et al. The mechanical properties of the respiratory system and its component parts are studied by determining the corresponding volume-pressure (V-P) relationships. The consequences of the inflam-matory response on the lung structure and function are depicted on the volume-pressure relationships. Expiratory flow limitation is well discussed by Tantucci. When expiratory flow is maximal during tidal breathing and cannot be increased unless operative lung volumes move towards total lung capacity, tidal expiratory flow limitation (EFL) is said to occur. In any circumstances, EFL predisposes to pulmonary dynamic hyperinflation and its unfavorable effects such as increased elastic work of breathing, inspira-tory muscles dysfunction, and progressive neuroventilatory dissociation, leading to reduced exercise tolerance, marked breathlessness during effort, and severe chronic dyspnea. N. G. Koulouris et al. in their paper discuss the expiratory flow limitation in COPD patients at rest (EFLT). EFLT, namely, attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. EFLT leads to small airway injury and promotes dynamic pulmonary hyperinflation with concurrent dyspnea and exercise limitation. Among the currently available techniques, the negative expiratory pressure (NEP) has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, noninvasive, most practical, and accurate new technique. COPD is a complex pathological condition associated with an important reduction in physical activity and psychological problems that contribute to the patient's disability and poor health-related quality of life as it is stated in …