CO2Elimination

CO2 elimination is the process of removing carbon dioxide produced by cellular metabolism from a system. In humans and many animals, the primary site is the lungs, where CO2 diffuses from blood into the alveolar air and is exhaled. In enclosed environments such as submarines or spacecraft, CO2 elimination may require dedicated ventilation management or chemical scrubbers to maintain safe air quality.

In physiology, CO2 is generated in mitochondria and transported in blood mainly as bicarbonate (HCO3−). A portion is dissolved as CO2 or bound to hemoglobin. In the lungs, CO2 diffuses from blood into alveolar air and is exhaled, a process driven by differences in partial pressure of CO2 between blood and air. Alveolar ventilation therefore governs the rate of CO2 elimination.

Regulation: the bicarbonate buffering system helps maintain acid–base balance while respiration adjusts to maintain appropriate CO2 levels. Central chemoreceptors in the brainstem respond to PaCO2 and pH, increasing or decreasing ventilation. Peripheral chemoreceptors in the carotid bodies also contribute to ventilatory drive.

Clinical and environmental relevance: impaired CO2 elimination occurs with hypoventilation or severe respiratory failure, leading to hypercapnia. Hyperventilation reduces CO2, potentially causing hypocapnia. Therapeutic approaches include mechanical ventilation or extracorporeal CO2 removal in refractory cases, while in closed environments, scrubbers or controlled ventilation are used to remove CO2 from air.

Measurements: PaCO2 in arterial blood and end-tidal CO2 (EtCO2) reflect elimination efficiency. Normal arterial PaCO2 is about 35–45 mmHg; EtCO2 approximates alveolar CO2 during steady ventilation.