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NBME 22 Answers

nbme22/Block 4/Question#4 (reveal difficulty score)
A 24-year-old man who is comatose is admitted ...
25 mL/cm H2O ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–

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 +28  upvote downvote
submitted by โˆ—alwaysanonymous(35)

His tidal volume was 500 mL. End-expiratory was +5 cm and end-inspiratory was +25. We were supposed to use the difference in airway pressure, and not the end-inspiratory pleural pressure (+20).

Compliance = ฮ”V/ฮ”P = 500 / 20 = 25 mL/cm H2O

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some-zheimers  Great explanation. In general, also a great idea to pay attention to the units. I studied Physics in undergrad and have got one or two questions based purely on following the units, when the formula slips. +29
endochondral1  is that equation in FA? +
redvelvet  yes @endochondral1, at page 651 in 2019FA +20
chaosawaits  any time you see the word compliance, ฮ”V/ฮ”P should immediately pop into your head. But my question is, coming from complete ignorance, is it just a coincidence that the end-inspiratory pleural pressure is equal to the difference of the needed values? +

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