Capnia refers to which of the following?

• A. O2 blood levels
• B. CO2 (Carbon Dioxide) Blood Levels
• C. Blood pH
• D. Bicarbonate levels

Answer: (B)

Capnia refers to the level of carbon dioxide in the blood. It indicates how effectively the lungs are eliminating CO2. When CO2 is high, it’s hypercapnia; when CO2 is low, it’s hypocapnia. CO2 levels influence acid-base balance because CO2 forms carbonic acid in the blood, so more CO2 tends to lower pH (acidosis) and less CO2 can raise pH (alkalosis). The other options point to oxygen content, blood pH, or bicarbonate, aspects related to ventilation or acid-base status but not capnia itself. In clinical practice, measuring CO2 levels or using capnography assesses ventilation rather than directly measuring oxygen tension or bicarbonate.