NBME 18 Physiologic shunt (NBME Answers)

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nbme18/Block 3/Question#45 (17.6 difficulty score)
65 yo patient with lung region ...
Physiologic shunt🔍
tags:

+9
submitted by banana(12),

If you got all tangled up on this question like me:

anatomic dead space= conducting airways

Alveolar dead space= alveoli that are ventilated but not perfused (wiki)

physiologic dead space=anatomic dead space+ alveolar dead space

Po2: just no

motherhen When I get mixed up on dead space vs shunt, I anchor myself on the meaning of anatomic dead space: the parts of the airway that don't have associated blood vessels for gas exchange (nose, trachea, bronchi). From there I work backwards to what shunt means: blood vessels that don't have enough air. +1

+0
submitted by sugaplum(323),

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+0
submitted by regents(0),

Good memory tip: to remember dead space, think "dead people don't have any blood flow"--> lung areas that are NOT perfused

In this case, the lung region is well perfused. So the answer must be shunt.