NBME11 spoiler - respiratory question - exam tomorrow - please, fast answer!

[Phloston]

---

Members do not see this ad.

A 25-yr-old man comes to the ER five hours after developing SOB and chest pain while exercising; he has had no cough or bloody mucous. He has asthma and major depressive disorder. Current medications are fluticasone inhaler and albuterol. He is afebrile. HR = 110. RR = 30. BP = 90/60. O2 sat = 93%. Cardiac exam shows normal S1/S2 and no murmurs or increase in JVP.

Hb = 13 g/dL
Hct = 39%
Arterial Blood gas:
pH = 7.46
pCO2 = 26 mm Hg
pO2 = 60 mm Hg

--------

A CXR is shown. Which of the following findings is most likely in this patient?

A) Crackles on the left lung base and apex
B) Crackles on the right lung base
C) Decreased breath sounds on the left
D) Increased wheezes on the left
E) Rhonchi on the right

Then they show an image (that I'm not allowed to post for Copyright reasons, but is available as question #13 in section #1 on this link: http://www.scribd.com/doc/110644085/NBME-11-With-Answers ; btw, that link is fickle, so it can sometimes take a few tries before it works), but it appears as though the right lung is normal but the left lung is most definitely hyper-expanded. And you can see that the trachea is deviated heavily to the right. Basically it appears like a tension-pneumothorax, but I can't logically see that being the case here.

The answer is apparently choice C, but I need someone who's seen this question to explain what's going on here.

Thanks so much,

 

[sarcoplasm]

Pneumothorax.
Dont think the left lung is hyper expanded..
Also low BP.. likely that it is indeed a tension pneumothorax.

 

[ijn]

Tachycardia, tachypnea, hypotension, hypoxemia, tracheal deviation, absent breath sounds... that's classic tension pneumothorax. The only symptom he is missing is JVD, but it's close enough to make a diagnosis and stick a chest tube in that sucker. He originally started with primary spontaneous pneumothorax and 1-2% of those will progress to tension pneumothorax. Are you not clear on why tension = that symptom constellation? The tension pneumothroax causes the heart to shift in the thorax, leading to the SVC/IVC to kink off since they're so malleable. Loss of venous return results in compensatory tachycardia and the back pressure causes JVD.

The thing I don't understand is that he's having hemodynamic compromise. Why did the question writer bother to include an x-ray of a collapsed lung? The patient should have gotten a chest tube first. Instead the patient died while the question writer waited on the X-ray tech to come down to the ER to confirm a diagnosis he should have made before imaging.

 

[Mdard]

Sorry...do you just not see the collapsed lung on the CXR? The asthma made me think D, but the hyperventilation and hypotension suggests something else, and you can SEE the collapsed lung and tracheal deviation on the CXR.

As for the blood:
atelectasis → stimulation of J receptors → ↑ work of breathing → dyspnea → hyperventilation → ↓PCO2 & ↑pH