Hemoglobin and Red Cell Adaptation When Oxygen Is Lacking

A number of conditions challenge hemoglobin’s ability to acquire and deliver oxygen. One is high altitude, where atmospheric pressure and oxygen tension are reduced. Serious lung disease can restrict breathing, or impose a barrier between the alveoli and blood, or create a mismatch within the lungs between the places with the best ventilation and those with the best blood flow. Some congenital heart diseases and vascular abnormalities permit some of the blood returning to the heart to bypass the lungs without being reoxygenated. Anemias of diverse causes reduce the blood’s oxygen carrying capacity. And some congenital hemoglobin variants do not bind or release oxygen normally. Investigations into the nature of all of these have generated mountains of research papers and have uncovered fascinating details about how humans and other animals respond or adapt to oxygen adversity.