NBME 21 Increased radial traction on airways (NBME Answers)

NBME 21 Answers

nbme21/Block 3/Question#2 (reveal difficulty score)
A 40-year-old man with interstitial pulmonary ...
Increased radial traction on airways 🔍 / 📺 / 🌳 / 📖
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submitted by ∗benzjonez(48)

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Uworld Qid 1543 has a good explanation as to how pulmonary fibrosis increases the radial traction on the airway walls.

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cienfuegos I think this is it -pulmonary fibrosis increases elastic recoiland widens airway 2/2 increased outward force (radial traction) by fibrotic tissue thus decreasing airflow resistance thus supernormal expiratory flow rates (higher than nl following correction for lung volume) +4

notyasupreme ^ Why do I feel like this is literally not english, I have no clue what's being said here. Can someone else explain it? +2

skonys Radial Traction is basically the force that the surrounding scaffold of the lung parenchyma exerts on a brochial tube to keep it patent when youre breathing. In restrictive lung disease (interstitial pulmonary fibrosis) youre adding more fibrous scaffolding around the tube which keeps BIG open. These patients have a greater than FEV1 than you would think. They are taking in less air into their restricted lungs but that lung tissue has a much hhigher elastic recoil so what air they bring in is forced out through patent brochioles that are held open. In some obstructive lung diseases like emphasema, you have elastases tearing up the scaffolding holding the tubes open and these tubes naturally want to collapse so they do. They have less "traction" force radially around the tube holding it open so air is trapped. +2

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submitted by ∗nwinkelmann(366)

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In case anyone is a dense as I am and just didn't understand/remember what exactly expiratory flow is = FEV1. In restrictive conditions, FEV1 is normal or increased due to decreased FVC. Interstitial fibrosis = increased airway parenchyma scaffold around the airways, which is what provides radial traction. The greater the radial traction, the lower the collapsing force, and so expiratory flow is increased.

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champagnesupernova3 FEV1 is increased due to greater recoil of the lung tissue. FEV1/FVC is increased bc of that and bc of decrease in FVC +1

mangotango But I thought with restrictive diseases, the FEV1 dec a little and FVC decreases a lot, yielding an FEV1/FVC ratio that's normal or increased?? +2

an_improved_me Yea the OP is wrong here. FEV1 does NOT equal expiratory flow rate. FEV1 is not a really a rate; its a volume of air pushed out in 1 second specifically. This will be decreased in a pt with ILD. This is because the volume of the lung decreases (due to increased elastic recoil). Expiratory flow rate (in this question) will be elevated, b/c of the answer stated. From uworld: "[fibrosis] causes increased lung elastic recoil, as well as airway widening due to increased outward pulling (radial traction) by surrounding fibrotic tissue. The resulting decrease in airway resistance leads to supernormal expiratory flow rates (higher than nromal when corrected for lung volume)". +3

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submitted by ∗visualninjacontender(18)

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Pulmonary fibrosis will involve granulation tissue (as it is fibrosis). Granulation tissue includes myofibroblasts, which will "pull" on the airways, thereby increasing radial traction.

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sahusema The fibrosis causes contraction, the airways are pulled open giving less resistance to airflow +1

https://o.quizlet.com/XIqQUx.6YJFeQ-ACk9pWvA.png

radial traction emphysema vs fibrosis

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