Final answer:
Difficulty in breathing is known as dyspnea, which can be caused by various factors including reduced lung compliance or increased airway resistance due to conditions like COPD, fibrosis, or asthma.
Step-by-step explanation:
The difficulty in breathing is commonly referred to as dyspnea. Dyspnea is a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity. The causes of dyspnea are varying and might involve direct physiological effects, such as a change in the level of physical fitness or potential pathological conditions like Chronic Obstructive Pulmonary Disease (COPD), fibrosis, asthma, or emphysema. Changes in the compliance and resistance of the lung affect both breathing and gas exchange. Reduced compliance can make exhalation difficult and lead to air becoming trapped in the lungs, while increased resistance can obstruct airways and cause similar difficulties. The term sleep apnea refers to a disorder where breathing repeatedly stops and starts during sleep, but this condition is different from the generalized difficulty in breathing termed dyspnea.