NBME Step 2 CK Form 8 Constriction of vessels in the lungs (NBME Answers)

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submitted by ∗step_prep(148)

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Elderly woman with chronic COPD history presents with weight loss, progressive shortness of breath and light-headedness found to have JVD with RV heave and loud S2 (all components of pulmonary hypertension) and signs of congestive hepatopathy, all consistent with Group 3 pulmonary hypertension
Key idea: In most capillary beds of the body, decreased oxygen leads to vasodilation in order to facilitate more bloodflow to the area to maintain perfusion, but the lungs are the one exception in which decreased oxygen leads to constriction of blood vessels feeding that area so that blood is preferentially sent to well-oxygenated portions of the lung to minimize V/Q mismatch, but can lead to cor pulmonale in patients with COPD because their entire lungs are poorly oxygenated, leading to diffuse vasoconstriction and increased afterload on right ventricle

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uslme123 ... does the chicken or egg come first?? Doesn't become corpulmonale until there are signs of RV failure -- (Ventricular failure = increased chamber pressures & failure to supply adequate CO ) ...... This person has had increased pulmonary resistance for YEARS -- what changed recently is her RV finally was like f this and can no longer pump. Stupid question +1

jlbae I get what you are saying, but tell us what option other than constriction of vessels in the lungs answers the question. 2 answers refer to blood flow, not pressure. The other two (mi and decreased viscosity) are flat out incorrect. +2

kstudy Another semantic question... if constricted vessels cause less blood flow, it's silly to have both of those choices in the same question. Great example of why right-brained minds struggle on these questions. +