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NBME 23 Answers

nbme23/Block 2/Question#42 (56.8 difficulty score)
A 63-year-old woman comes to the physician ...
FVC: decreased;
FEV1/FVC: decreased;
Peak expiratory flow rate: decreased;
Peak inspiratory flow rate: decreased


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submitted by nwinkelmann(282),
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9h88@g sucB"aee hte ouribotntsc is abveo het oavreall orsngie eerht is a deeeacsr ni air of,lw nto unlg o,ulvmse which oudlw mkea tish an ceovsbuttir otygpla"oh is eht tsmo lhpeful anap.neltxoi If uyo nwko hte toms baisc etypanfgs/hootylohdinipoii of crvttiuebos sv ietrsrcevit iwch(h I do, sujt idtd'n ni taht smot diiesilmfp y,wa) hetn uyo can gifure ianhntyg o.tu fI ihmngteos si iigtampcn iwaray wlfo = sveouctrit,b if estihgonm si miaingtcp wiraya uleovm = .teiersivctr KNHAT UY!O

burningmoon  How about emphysema? airway volume changed but it's obstructive. +2  
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! +3  

submitted by xkno(5),
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I guthvhteoor hist one ibg itme. nSeic the iuqotnes said teh smas swa rniepsgs no hte todueis of the acarth,e I ruidfeg taht ugirnd nitans,rioip /bc eht eshct asdpex,n so rmoe ac,pse so het asms oduwl ehva ssle tfeefc on the caearht as hte estch dsanpxe n(ad eoesnrc,ylv idt' heva oerm fo na ffceet ugndir ernaoxtipi sa eth sthce llwa lnpyAarep,t it saw just sgtaithr up egbcaklo dan I hhgtout ayaaw ot hrd.a pos.O

submitted by usmleuser007(370),
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Lkei any fo the OPD,C het tpaient ahs a cftufdili meti lgenhxai teh irsndiep ari ust(h tis cedlla an orustbtcvei sae)dise

PDCO uletrss ni VFC dreeecs,a FCFVVE/1 rtaio esereacd, RFC rcsnie,ae nad epke iatxroepy oflw erdcs.eea

A tromu or any etorh cbtjeo atht owudl secprmos on ro ornawr ehste hte air awy ractt dwoul etresnp as a DCO.P

inIlganh and lexhagin ludow be itimled

submitted by .ooo. (29),
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I splnreoyal uhhttog of tihs sotsqniue thkgnnii fo ti ni teehs estm.r. encSi eth nepttai hsa a assm ni the hcrtaea keap irteapyrxo dan arorsitnyip wlof llwi be iupener,tdrt nad dwluo hfertoere eb redde.ecsa 1VCF lwudo lsoa evha to creedsea by h.sti siTh tadinlmeei all teh thero cces.iho

charcot_bouchard  Are you Me? +1  

submitted by visualninjacontender(16),
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tI doluc be hatt hsti si a dexfi pupre rayiwa ourntsbotc,i wihhc ulowd evnprte aftoilnin nda lnoeiatfd of eht ysriwaa ued to eth mutro lgpmcani odwn on eht care.hta

submitted by azibird(158),

Why is there a decreased FVC? There is a mass pressing on her trachea, how could that possible affect lung volume? If we give her enough time, why couldn't she take in a full breath?

submitted by mrglass(34),

I figured this was a variable intrathoracic obstruction and got it wrong.

According to UpToDate, INTRAluminal tracheal obstruction is varaible, while EXTRAluminal tracheal obstruction (like in this case) is fixed.

submitted by ninja3232(7),

To think about this simply, it literally is an obstruction so you can just choose the answer with the COPD like PFTs.

It's a bit counterintuitive that the FVC would be decreased, but the reason for this is because at the end expiration for FVC, the positive pleural pressure pushing the air out has equalized with the pressure of the atmosphere / airway wanting to keep the alveoli open. With an increase in the airway resistance from the obstruction, this equalization point comes at a higher FVC. Somebody fact check me please

submitted by donttrustmyanswers(56),

"disproportionate reduction in the peak expiratory flow rate or maximum minute volume compared with the forced expiratory volume in one second (FEV1). It should be noted, however, that there can be a significant loss in airway cross-sectional area before the textbook flattening of the inspiratory or expiratory loops are visualized."

mamed  google fixed upper airway obstruction - the spirometry curve shows decreased inspiration and expiration. A lower airway obstruction just blunts expiration. Extrathoracic blunts inspiration. +  

submitted by docred123(6),
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iH uysg nca noeosme epasle eeaatrlob on tsehe sfnnii.dg I rstddanune hes sah ulgn narecc tt'has ednipgmi erh rat.echa But owh is iths raetpeirntsvee of na ciboutvrtes d?rsidero rA'ten ulgn eacncrs esirteivctr if tag?nnhiy s hnkaT

nlkrueger  I agree that it's confusing but I looked at it as a physical *obstruction* since it's impinging on the airway.... but yeah idk this is weird +  
ferrero  Doesn't the trachea have cartilage rings so it wouldn't collapse which makes it seem less like a typical obstructive disorder? I'm really not sure why FVC would change because I don't see how total lung capacity or residual volume would change because those are static conditions where there is no airflow at all. I understand FEV1, peak expiratory flow, peak inspiratory flow etc. +2  
mousie  Agree this is a really tough Q but I also think I really over thought it... I eliminated all with a normal Ratio bc something obstructing would obviously produce an obstructive pattern although I don't know why FVC would be decreased. I wasn't sure about both peak expiratory and inspiration flow being decreased can someone help me with this or tell me I'm totally overthinking again.. are they both decreased simply bc theres an obstruction ..? +3  
mimi21  Yea I got confused on this question. But I guess they wanted us to look at it as a obstructive disease . If this were the case all of those function tests would dec. ( See FA ) +  
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. +3  
charcot_bouchard  FVC here dec same way it dec in Obstructive lung disease. Read the concept of Equal pressure point of BnB. There he says in bronchitis we have onstructive pattern because inflammed airways gen more resistance. so EPP comes early. I guess here due to tracheal narrowing pressure inc downstream. which collapses smaller airway. result in air trapping. +1