– Comparison of Key Differences Key TermsĪlveolar Dead Space, Alveoli, Capillary Shunt, Dead Space, Gas Exchange, Perfusion, Shunt What is the Difference Between Shunt and Dead Space What are the Similarities Between Shunt and Dead SpaceĤ. – Definition, Characteristics, Importanceģ. Moreover, they are examples of the ventilation-perfusion (V/Q) mismatch. Shunt and dead space are two conditions of lungs, resulting in impaired gas exchange. Pulmonary embolism (PE) is an example of increased dead space resulted in decreasing perfusion relative to ventilation. For example, in pneumonia, the area of the alveoli is well perfused although it is not well ventilated, leading to the shunt. Uworld says this is v/q mismatch but that gets me confused cause why wouldn't a vent defect give v/q mismatch.The main difference between the shunt and dead space is that shunt is the pathological condition in which the alveoli are perfused but not ventilated, whereas dead space is the physiological condition in which the alveoli are ventilated but not perfused. That's why you will see a drop in PaO2 in PE(minor). So this one is tougher but: Let's assume you have a well ventilated alveoli, when there is poor oxygen content, vasculature will constrict and redistribute this blood to other alveolar however it will overwhelm the capacity of extracting oxygen into blood - so adding oxygen will help. Dead space/physiologic dead space/V/Q mismatch to inifinty.

I remember total pulm shunt as if pulm art partial pressure = pulm vein partial pressure, shunted, basically just bypassed lungs. These alveolar are already extracting maximum oxygen, adding more would not help. Lets assume this kid have some alveoli that are working. pulm shunting - ventilation defect V/Q 0, perfusion intact.So this is my understanding of the topic and I might be wrong so please correct me if thats the case:

Shunt vs dead space question