Abstract

Patients with chronic obstructive pulmonary disease usually manifest decreases in functional capacity, endurance time at submaximal exercise, and maximal exercise performance compared to age- and sex-matched healthy individuals. The main pathophysiologic changes in this disease are obstruction of expiratory airways and/or pathologic alterations in the lung parenchyma. Many factors are associated with decreased exercise tolerance, including increased airway resistance, inadequate ventilation, increased elastic loading of ventilation, hyperinflation, gas exchange abnormalities, mechanical weakness of respiratory muscles, and varying degrees of disturbances in the central and peripheral nervous systems due to hypoxic response. Skeletal muscles also undergo pathological changes similar to those in ventilation muscles. All these result in decreases in functional capacity and exercise tolerance, giving rise to dyspnea during minimal activity and even at rest. In order to break this vicious circle, supporting rehabilitation programs have to be combined with medical treatment.