According to latest research by a team led by cardiologist Jonathan Stamler, of the University School of Medicine in Cleveland in the United States, the respiratory cycle involves a third gas, nitric oxide. Until now the understanding was that it involved only two gases, oxygen and carbon dioxide.
In their study the researchers show that hemoglobin - the protein in red blood cells that picks up oxygen from the lungs - also needs to carry nitric oxide to enable blood vessels to open and supply the oxygen to tissues.Prof.
Stamler says, "blood flow to tissues is actually more important in most circumstances than how much oxygen is carried by hemoglobin. So the respiratory cycle is actually a three-gas system."
For some time doctors have known there is an imbalance between the amount of oxygen transported in the blood and the amount that is delivered to tissues - but not why. The new study shows they have discovered the molecular basis of what controls blood flow in the respiratory cycle.
The findings have implications on research into heart attacks and strokes, where it was believed that blood flow was controlled only by blood vessels.
The new findings show red blood cells also play an important role. The study also has implications for blood transfusions. Recent evidence shows blood transfusions lacking nitric oxide are linked to higher risk of heart attacks, disease and death.