Bohr Effect

Picture of red blood cells

The Bohr effect, first described by Danish physiologist Christian Bohr in 1904, is a result of the effect carbon dioxide has on hemoglobins affinity for oxygen.

As carbon dioxide increases, it combines with water to form carbonic acid. This increase in acid lowers the pH. The lowered pH then decreases hemoglobins affinity for oxygen, meaning hemoglobin lets go of oxygen more easily. As a result, more oxygen is released to the muscles and tissues that need it most. 

Conversely, decreases in carbon dioxide will increase hemoglobins affinity for oxygen, meaning hemoglobin is less likely to release oxygen. Thus, the relationship between CO2 and hemoglobins affinity for oxygen can be described as an inverse relationship meaning when one goes one way, the other goes the other way.

Gif showing the Bohr and haldane effect
Observe the changing levels of oxygen and carbon dioxide that are bound to hemoglobin as a red blood cell travels from the lungs to metabolically active tissue throughout the body.

By Rogeriopfm – Own work, partly based on File:Grafik blutkreislauf.jpg by Sansculotte., CC BY-SA 3.0,

Why is the Bohr effect important?

The Bohr effect is important because it enhances delivery of oxygen to the muscles and tissues where metabolism is occurring and carbon dioxide is being produced. This helps deliver oxygen where it is most needed.

Picture an asthmatic patient who is working very hard to breathe. They are using their accessory muscles of respiration, such as the diaphragm and sternocleidomastoid muscles, close to the point of exhaustion. These muscles are working extremely hard and producing a lot of CO2 as a result. However, due to the Bohr effect, oxygen delivery is enhanced to those muscles. So, as CO2 increases in those muscles of respirations, oxygen delivery to those muscles also increases.

Picture of Christian Bohr
Danish physiologist Christian Bohr
About Damon Wiseley 9 Articles
Lead writer at Respiratory Cram RRT-CPFT B.H.S.c. Nova Southeastern University