Hypercapnia refers to a higher than normal level of carbon dioxide in arterial blood. In a person with normal metabolism, this automatically triggers an increased respiration rate in order to bring in more oxygen.

Some of the other signs of hypercapnia are flushing of the skin, increased pulse rate, rapid breathing, shortness of breath, muscle twitches and increased blood pressure.

It is usually caused by slow breathing, lung diseases or diminished consciousness. It is very common among SCUBA divers.

In most cases, the condition is self-correcting as the breathing rate expels carbon dioxide more rapidly until normal breathing resumes. In a patient with lung problems, supplemental oxygen is often required.

Hypercapnia at Wikipedia