An additional result in severe cases is that the carbon dioxide produced in the body by everyday metabolism can no longer be exhaled adequately, and accumulates in the blood. Some individuals are more sensitive to nicotine and to cigarette smoke than are others. In addition, an occasional nonsmoker may develop the syndrome, either through congenital chemical imbalances, occupational exposures, or unknown factors. The first symptom of emphysema is usually shortness of breath on exertion. Chronic bronchitis usually has a longstanding cough as its first warning.
Most patients have a mixture of the two.
As the disease progresses, shortness of breath increases such that in the end, even speaking more than a few words at a time is too much. Low blood oxygen is not always present, and in fact is unusual in emphysema, as compared to bronchitis. When low oxygen levels are present, the lips and digits may appear blue or dusky, and cardiac or cerebral symptoms may appear. As the terminal stages are approached the patient begins to lose weight as eating becomes difficult, and energy is spent breathing through the damaged lungs. The slightest respiratory burden such as a mild cold, or the use of even mild sedatives is enough to cause respiratory failure, and periods on a mechanical ventilator become necessary if the patient survives.