ABSTRACT
When questioned carefully, patients with different cardiorespiratory disorders fre quently describe distinct qualities of breathing difficulty (Table 1). As each of the seven diagnoses was associated with a unique set of descriptors, it is likely that these different experiences relate to the pathophysiology of the specific condition. For example, patients with chronic obstructive pulmonary disease (COPD) typically reported th a t4 ‘My breathing requires effort,” and “ It is hard to breathe.” When patients with COPD perform even trivial physical tasks, they develop dynamic hyperinflation (i.e., they breathe at a higher lung volume) in order to increase expiratory airflow. One consequence of hyperinflation is an increase in the elastic recoil of the lung. This adaptation places an added load on the diaphragm, which is also functionally weakened due to shortening of the vertical mus cle fibers. These alterations presumably contribute to the “ work and effort” of the respira tory muscles during physical activities in patients with COPD. The cluster “ work/effort” characterized all seven diseases reported in Table 1. This finding, along with the observa tion that patients identified that dyspnea was experienced more frequently during inspira tion rather than during expiration, supports the concept that respiratory muscles are impor tant in the experience of dyspnea.
