Final answer:
Hypercapnia refers to an abnormally high level of CO2 in the blood, commonly caused by impaired respiratory functions or hypoventilation, and is associated with respiratory acidosis.
Step-by-step explanation:
The term hypercapnia specifically refers to a condition where there is an abnormally elevated level of carbon dioxide (CO2) in the blood. This state often occurs when respiratory functions are impaired due to conditions like pneumonia or congestive heart failure, or due to hypoventilation (reduced breathing) from the effects of certain drugs or even voluntarily holding one's breath. Generally, hypercapnia indicates inadequate ventilation relative to the metabolic demands, resulting in an excess of carbonic acid in the bloodstream, which can lead to respiratory acidosis.
Hypercapnia should not be confused with hyperpnea, which is an increased rate and depth of ventilation, often seen during exercise or when the body has an increased demand for oxygen but does not necessarily result in significant changes in blood CO2 levels. Nor should it be conflated with hyperventilation, which is an increased ventilation rate that exceeds the body's need for oxygen and leads to decreased blood carbon dioxide levels and increased blood pH, a condition known as respiratory alkalosis.