Final answer:
Patients with COPD typically have a chronically high level of carbon dioxide in the blood, known as hypercapnia, due to impaired gas exchange and air trapping in the lungs.
Step-by-step explanation:
Patients with chronic lung diseases such as Chronic obstructive pulmonary disease (COPD) often have a chronically high level of carbon dioxide (CO2) in the blood, a condition known as hypercapnia. COPD includes conditions formerly referred to as chronic bronchitis or emphysema. This disease is characterized by a breakdown of connective tissues of the alveoli, decreasing both the number and elasticity of these vital structures. Consequently, patients are unable to fully exhale air from their lungs, leading to trapped air, impaired gas exchange, and thus, elevated levels of CO2 in the blood.
Hypercapnia can also occur in other respiratory function impairing situations like pneumonia and congestive heart failure, or due to hypoventilation caused by drugs like morphine and barbiturates. On the other hand, hyperventilation due to factors like fever or salicylate toxicity can cause hypocapnia, an abnormally low level of CO2 in the blood.