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A pulmonary shunt is the passage of deoxygenated blood from the right side of the heart to the left without participation in gas exchange in the pulmonary capillaries. It is a pathological condition that results when the alveoli of parts of the lungs are perfused with blood as normal, but ventilation (the supply of air) fails to supply the perfused region.
The Shunt equation (also known as the Berggren equation) quantifies the extent to which venous blood bypasses oxygenation in the capillaries of the lung.. “Shunt” and “dead space“ are terms used to describe conditions where either blood flow or ventilation do not interact with each other in the lung, as they should for efficient gas exchange to take place.
The circulation of a patient after BDG shunt placement requires adequate systemic venous return to support pulmonary blood flow. However, pulmonary blood flow, and thus oxygenation, is inhibited by high pressures or valvular obstructions. [1] Pulmonary hypertension (moderate to severe) is a relative contraindication to the bidirectional Glenn. [5]
The partial pressure of oxygen (pO 2) in the pulmonary alveoli is required to calculate both the alveolar-arterial gradient of oxygen and the amount of right-to-left cardiac shunt, which are both clinically useful quantities. However, it is not practical to take a sample of gas from the alveoli in order to directly measure the partial pressure ...
Secondly, the pulmonary shunt is caused by zero or low V/Q ratio due to insufficient ventilation and excess perfusion. Improper ventilation lowers blood oxygenation and oxygen supply to body tissues. Although 100% oxygen is inspired, a pulmonary shunt prevents oxygen from being delivered to the alveoli and blood capillaries.
The pathophysiology of acute respiratory distress syndrome involves fluid accumulation in the lungs not explained by heart failure (noncardiogenic pulmonary edema). It is typically provoked by an acute injury to the lungs that results in flooding of the lungs' microscopic air sacs responsible for the exchange of gases such as oxygen and carbon dioxide with capillaries in the lungs. [1]
A pulmonary-to-systemic shunt is a cardiac shunt which allows, or is designed to cause, blood to flow from the pulmonary circulation to the systemic circulation. [1] [2] This occurs when: there is a passage between two or more of the great vessels; and, pulmonic pressure is higher than systemic pressure and/or the shunt has a one-way valvular ...
Eisenmenger syndrome or Eisenmenger's syndrome is defined as the process in which a long-standing left-to-right cardiac shunt caused by a congenital heart defect (typically by a ventricular septal defect, atrial septal defect, or less commonly, patent ductus arteriosus) causes pulmonary hypertension [1] [2] and eventual reversal of the shunt into a cyanotic right-to-left shunt.