NBME Answers : burningmoon's page

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+15 visit this page (nbme21#25)

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Water(1) 1Kg water=1L water 450mOsm/kg water=450mOsm/L water Min H2O needed to dissolve 450 solute by kidney is 1L water Water(2) Other (feces et al.)=1L Total: water(1)+ water(2)=2L

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ali_hassan this is what i needed +

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submitted by nwinkelmann(366), visit this page

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@gh889 "Because the obstruction is above the alveolar regions there is a decrease in air flow, not lung volumes, which would make this an obstructive pathology" is the most helpful explanation. If you know the most basic definition/pathophysiology of obstructive vs restrictive (which I do, just didn't in that most simplified way), then you can figure anything out. If something is impacting airway flow = obstructive, if something is impacting airway volume = restrictive. THANK YOU!

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burningmoon How about emphysema? airway volume changed but it's obstructive. +3

almondbreeze i think OP meant to say that something DECREASING airway volume = restrictive +3

jgraham3 I think they mean if something is impacting LUNG volume (ie. expansion/compliance) = restrictive Airway disorder --> obs. / Parenchymal disorder --> res. With emphysema the airway collapses (obs.) before they are able to exhale fully thus the air is trapped +

dna_at Just to be clear, this is not a classical obstructive lung disease affecting the small airways, as it is above the carina (trachea). This is better classified as a fixed upper airway obstruction. See the flow loop here for "fixed obstruction" - it came up in IMED UWorld so maybe familiarize yourself with the image since it is unique! https://www.grepmed.com/images/2948 +4

notpennysboat @dna_at, can you explain the concept of the upper airway obstructions? I'm still pretty confused +