1.    Chronic Obstructive Pulmonary Disease is an umbrella term for the combination of varying degrees of conditions affecting the respiratory system, namely bronchial asthma, chronic bronchitis and emphysema.
2.    Chronic bronchitis is associated with changes to the structure of bronchial walls due to long term exposure to stimulants such as smoking, which leads to inflammation and increased mucus production.
3.    Cessation of smoking, antibiotic therapy, beta-2 agonists for bronchodilation, oxygen inhalation therapy, rehydration and steaming to dilute mucus, antibiotic therapy and regular light exercise to improve lung capacity. 
4.    They have influence on the vagus nerve and are long-acting which is beneficial in chronic bronchitis, where as in bronchial asthma beta agonists are preferred for quick action.
5.    Theophylline improves the contraction of diaphragm skeletal muscles improving ventilation.
6.    To improve hypoxia.