What happens to the carbon dioxide produced by your body during period of apnea?

During a period of apnea, the partial pressure of carbon dioxide in the blood increases as a result of ongoing production of carbon dioxide by the body's metabolism but the absence of ventilation to remove it from the lungs. This increase stimulates the respiratory center causing a feeling of the desire to breath and eventually leading to the resumption of spontaneous breathing. Carbon dioxide acts as a potent respiratory stimulant in this context ensuring that breathing resumes promptly after a period of apnea, to restore appropriate gas exchange and prevent severe respiratory and systemic consequences.