Saturday December 5, 2009


Q: What is Haldane effect?

Answer: The Haldane effect (named after John Scott Haldane) describe that deoxygenation of the blood increases its ability to carry carbon dioxide. Conversely, oxygenated blood has a reduced capacity for carbon dioxide.

The Haldane effect promotes dissociation of carbon dioxide from hemoglobin in the presence of oxygen. In the oxygen-rich capillaries of the lung, this property causes the displacement of carbon dioxide to plasma as venous blood enters the alveolus and is vital for alveolar gas exchange.

This partially explains the observation that some patients with emphysema might have an increase in PaCO2 following administration of supplemental oxygen even if content of CO2 stays equal.

Oxygenation of Hb promotes dissociation of H+ from Hb, which shifts the bicarbonate buffer equilibrium towards CO2 formation; therefore, CO2 is released from RBCs.