Which condition is characterized by high levels of carbon dioxide in the blood?

The condition characterized by high levels of carbon dioxide (CO2) in the blood is known as hypercapnia. This occurs when the body is unable to effectively eliminate CO2, leading to excessive accumulation in the bloodstream. Hypercapnia can result from various factors, such as respiratory failure, chronic obstructive pulmonary disease (COPD), or hypoventilation, which can impede proper gas exchange in the lungs.

In contrast, hypoxia refers to low levels of oxygen in the tissues, not an increase in carbon dioxide. Acidosis is a condition where the blood becomes too acidic, which can occur secondary to hypercapnia but is not synonymous with it. Alkalosis indicates that the blood is too basic, which again does not relate directly to the high levels of carbon dioxide. Therefore, hypercapnia specifically addresses the elevation of CO2 in the blood, making it the correct choice in this context.