doc_clotaire
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A 54-year-old woman with a long history of emphysema presents because of an exacerbation of her cough and dyspnea. On physical examination, her blood pressure is 126/64 mm Hg, pulse is 82/min, and respirations are 24/min. On lung examination, there are loud expiratory wheezes and rhonchi. The cardiac examination is normal. An arterial blood gas is performed. Which of the following results would most likely be expected?
A. pH of 7.20, pCO2 of 60, and pO2 of 46
B. pH of 7.30, pCO2 of 50, and pO2 of 94
C. pH of 7.35, pCO2 of 45, and pO2 of 60
D. pH of 7.46, pCO2 of 25, and pO2 of 76
E. pH of 7.52, pCO2 of 30, and pO2 of 82
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| vradojc1
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C - pCO2 and pH are close to normal because of acute hyperventilation that due to the changes in diffusion capacity of the lung will not correct low pO2.
B - pO2 to high
A - pH would match rise in pCO2 if this were an acute condition (without previous disease). We should expect at least some compensatory response.
D/E - no alkalosis would be seen in chronic emphysema.
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| new_n_lost
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B. pH of 7.30, pCO2 of 50, and pO2 of 94 ??
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| doyoudig
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Hypoxemia & Hypercapnia ashuld be A
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| dr.wad
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my answer is D. pH of 7.46, pCO2 of 25, and pO2 of 76
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| Adam
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I'll go with A. (chronic COPD + exacerbation => hypercapnea, Hypoxemia ) ..
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| dr.wad
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in emphysema there is hpoxaemia and normal or hypocapnia due t hyperventilation
hyperventilation is the cause of hpocapnia and respiaratory alkalosis.
during acute attack hyperventilation will increase >>>washing more CO2 >>>>more hpocapnia>>>>> more alkalosis.
so that i guess the answer is D , although also suspecting E.
but i exclude E because PCO2 is higher than in D.
i hope the answer is correct . these topics indeed are confusing to me.
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| Justice
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(B)
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| dr.wad
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doc_clotaire ........could u plz post the answer.........
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| young_doc
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B?
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| doyoudig
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In COPD the probl is gas exchange so the Pt is retaining CO2 and not getting enough O2 but trying to hyperventilate to get more O2 unsuccessfully. Problem is Air getting out
In addition the alveoli are messed up impairing gas exchange
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| dr19
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I think we should distinguish between emphysema & bronchitis, in the first place.
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| Aashi
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C ----------> pH of 7.35, pCO2 of 45, and pO2 of 60
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| doyoudig
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what's the answer doc?
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| doc_clotaire
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The answer is C
This is cronic respiratory acidosis
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| Justice
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doc_clotaire wrote:
The answer is C
This is cronic respiratory acidosis
Well, for chronic resp acidosis the pCO2 of 45 is quite low...
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| NE
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yes, CO2 is low for chronic resp acidosis because she has and acute presentation now and hyperventilates!
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| Justice
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NE wrote:
yes, CO2 is low for chronic resp acidosis because she has and acute presentation now and hyperventilates!
And for that same reason pO2 should be higher...
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| NE
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CO2 has a greater diffusion index than O2 through alveolar membrane!
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| doyoudig
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what would the ABG be in a Pt if with Emphysema w/o the setting of acute hyperventialtion
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| doc_clotaire
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OK Guys ! Sorry for not posting the explanation earlier ! Here we go .................
This question is from Kaplan . Here is the exact explanation that they gave
The correct answer is C.
This patient has an acute exacerbation of her chronic obstructive pulmonary disease (COPD). On the basis of the history and physical examination, she would be expected to have a compensated respiratory acidosis because CO2 retention. Furthermore, she would be expected to have evidence of mild hypoxia. With respirations of 24/min, which is high but not extremely high, she would not be expected to show the severe levels of acidosis and CO2 retention illustrated in choice A. The patient is sufficiently symptomatic that the near normal pO2 of 94 seen in choice B would be unlikely. Although asthmatics may present during an acute exacerbation with a respiratory alkalosis (choices D and E), in a patient with underlying COPD, there is usually a baseline respiratory acidosis
FROM WHAT I UNDERSTAND
Some patients with COPD may have a mild respiratory acidosis with mild to moderate hypoxemia without hypercapnia . For these patients to have Hypercapnia , the FEV 1 would have to fall below 1 L / s or 30 % of the predicted value . Remember , COPD is cronic condition where the kidney are partially ( NOT TOTALLY ) trying to compensate that acid base disturbance reving up bicarbonate ( metabolic alkalosis )
That 's why you would see a BODERLINE RESPIRATORY ACIDOSIS ( ALMOST NORMAL ) and besides as the explanation said above : Choice A is for a SEVERE RESPIRATORY ACIDOSIS in extreme case of hypoxemia and you would find the respiratory rate even higher than 24 / min
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| ether
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Check out www.floeos.com I believe is an excellent calculator to help you with acid-base problems!
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| doyoudig
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thx much!!!
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