<P> A similar problem exists when inhaling certain odorless asphyxiant gases . These produce a hypoxic breathing gas which can produce unconsciousness and death without symptoms . This may cause inert gas asphyxiation . Such asphyxia may be deliberate with use of a suicide bag . Accidental death has occurred in cases where concentrations of nitrogen in controlled atmospheres, or methane in mines, has not been detected or appreciated . </P> <P> Hemoglobin's function can also be lost by chemically oxidizing its iron atom to its ferric form . This form of inactive hemoglobin is called methemoglobin and can be made by ingesting sodium nitrite as well as certain drugs and other chemicals . </P> <P> Hemoglobin plays a substantial role in carrying oxygen throughout the body, and when it is deficient, anemia can result, causing' anaemic hypoxia' if tissue perfusion is decreased . Iron deficiency is the most common cause of anemia . As iron is used in the synthesis of hemoglobin, less hemoglobin will be synthesised when there is less iron, due to insufficient intake, or poor absorption . </P> <P> Anemia is typically a chronic process that is compensated over time by increased levels of red blood cells via upregulated erythropoetin . A chronic hypoxic state can result from a poorly compensated anaemia . </P>

Medical term for deficiency of oxygen in the blood