The etiological diagnosis is of basic importance in patients with emphysema because the distinction between primary and secondary types decides the plan of treatment. The general aim of treatment is to keep the patient active, to preserve as much lung tissue as possible, and to maintain comfort. In primary emphysema, breathing exercises and such expectorants as potassium iodide are helpful, and in severe cases oxygen is indicated if used with due caution. But in secondary emphysema it may be necessary to use bronchodilators and steroids to combat underlying bronchial asthma, antibiotics to stop destructive infections, and other therapy directed at the original cause.