Chronic bronchitis and emphysema are together called chronic obstructive pulmonary disease, or COPD. This is a chronic condition, usually attributed to tobacco smoking, causing shortness of breath and cough, leading to limitation of everyday activities like walking.
When breathing becomes more difficult for a person with COPD, they may be experiencing an acute exacerbation of COPD (AECOPD). During an acute exacerbation, breathing becomes more difficult because of further narrowing of the airways and secretion of large amounts of mucus that is often thicker than usual.