NBME 20 Subcutaneous crepitus (NBME Answers)

NBME 20 Answers

nbme20/Block 2/Question#20 (reveal difficulty score)
A 19-year-old man who is a college student is ...
Subcutaneous crepitus 🔍 / 📺 / 🌳 / 📖
tags: pulm

+21 upvote downvote
submitted by ∗strugglebus(189)

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Bronchophony= pneumonia Expiratory stridor= tracheobronchial obstruction (mass/foreign body) Inspiratory stridor = laryngeal obstruction Succussion splash= test for pyloric stenosis

When there is a fractured rib it will cause a trauma pnemothorax which can cause air to escape and become trapped under the skin leading to crepitus.

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charcot_bouchard Actually when a fractured rib puncture lung then it cause sc emphysema. +2

mbourne "Chest trauma, a major cause of subcutaneous emphysema, can cause air to enter the skin of the chest wall from the neck or lung. When the pleural membranes are punctured, as occurs in penetrating trauma of the chest, air may travel from the lung to the muscles and subcutaneous tissue of the chest wall. When the alveoli of the lung are ruptured, as occurs in pulmonary laceration, air may travel beneath the visceral pleura (the membrane lining the lung), to the hilum of the lung, up to the trachea, to the neck and then to the chest wall. The condition may also occur when a fractured rib punctures a lung; in fact, 27% of patients who have rib fractures also have subcutaneous emphysema. Rib fractures may tear the parietal pleura, the membrane lining the inside of chest wall, allowing air to escape into the subcutaneous tissues." +1

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submitted by rio19111(16)

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Diagnosis: Pneumomediastinum (FA 2019, 659)

+Hamman Sign=Crepitus on cardiac auscultation

Etiology: spontaneous (due to rupture of pulmonary bleb) or 2° (eg, trauma, iatrogenic, Boerhaave syndrome).

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md_caffeiner also look on FA 667 traumatic pnx where it says "rib fracture" +1

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submitted by ∗masonkingcobra(408)

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Here is a fantastic picture to understand

https://www.semanticscholar.org/paper/Pneumomediastinum-in-the-neonate.-Cagle/7b235daea2488612a1917009afc849afc3e262e7/figure/4

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-4 upvote downvote
submitted by ∗monoloco(155)

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I have regarded crepitus as the rubbing of bone-on-bone. My study partner and I think this is a purely definitional question. Yes, crepitus could also be trapped air. Context, I guess.

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medstudent65 Crepitus is used to describe bone-on-bone grinding. Subcutaneous crepitus is very specific sound referencing air finding its way into the skin which you can hear but also feel by rubbing your hand over the affected area. The addition of subcutaneous lets you know we are specifically talking about air in the skin. +1

len49 You may also see the word in regards to gas gangrene (C. perfringens soft tissue infection) FA 2019 pg 138 +2

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