The human body is organized in such a way that it constantly places a high priority on maintaining the level of oxygen in the blood. All you have to do is stop breathing for a few moments (apnea) to feel this urgent and irrepressible need to find air. Following an apnea, heart and breathing rates systematically increase. This is the body’s way of rapidly bringing oxygen saturation back to 100% and restoring the circulation of red blood cells to the tissues.
People with relatively severe anemia have symptoms of hyperventilation and a rapid heartbeat due to their bodies’ constant effort to restore oxygen levels to normal.