A<unk>  refers to the passage of deoxygenated blood from the right side of the heart to the left without participation in gas exchange in the<unk>  capillaries. It is a pathological condition that results when the alveoli of the lungs are perfused with blood as normal, but ventilation (the supply of air) fails to supply the perfused region. In other words, the ventilation/perfusion ratio (the ratio of air reaching the alveoli to blood perfusing them) is zero. A<unk>  often occurs when the alveoli fill with fluid, causing parts of the lung to be unventilated although they are still perfused. Intrapulmonary shunting is the main cause of hypoxemia (inadequate blood oxygen) in<unk>  edema and conditions such as pneumonia in which the lungs become consolidated. The shunt fraction is the percentage of blood put out by the heart that is not completely oxygenated. In pathological conditions such as<unk>  contusion, the shunt fraction is significantly greater and even breathing 100% oxygen does not fully oxygenate the blood.
Pulmonary shunt
Cardiac shunt
Atriocaval shunt
Pulmonary-to-systemic shunt
Pulmonary artery banding
Portacaval shunt
Blalock–Taussig shunt
Aortopulmonary window