MDcooper
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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?
.
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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| robin082006
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This patient has high respiratory rate--> resp alkalosis--> rule out A,B,and C.
This patient has COPD exacerbation--> I go with D as hypoxia.
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| mazinger
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In patients with COPD alveolar ventilation is not normal since its not normal eventhough they may be tachypneic (corrected this formerly I used hyperventilate) they cannot decrease PCO2 levels dramatically in fact it could still be increased... I go for C...
Edited by mazinger on 01/04/07 - 04:49 PM
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| MDcooper
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wont the pt hypoventilate in COPD?there will be inc PCO2 and hypoxia.there must be resp acidosis.we have to choose which values though.
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| mazinger
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whats the answer mdcooper? is it C? or A?
BTW I go for C
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| prathapdoctor
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I agree with robin,patient is tachypneic so there will be decrease in CO 2, i think it will not produce hypercapnea because its not even a restrictive disease,its an obstructive disease and the patient is tachypneic.
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| MDcooper
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answer is C.hypoxemia,with near normal pco2
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| fox
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Emphysema patients are pink puffers & chronic bronchitis patients are blue bloaters. In the stem, it says that the patient suffers from emphysema (restrictive Ds) & we expect co2 to be low, however there also seems to be a obstructive component in that there are wheeze & ronchi. So maybe thats the reason the CO2 is near normal, while there is hypoxia.
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| mazinger
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fox wrote:
Emphysema patients are pink puffers & chronic bronchitis patients are blue bloaters. In the stem, it says that the patient suffers from emphysema (restrictive Ds) & we expect co2 to be low, however there also seems to be a obstructive component in that there are wheeze & ronchi. So maybe thats the reason the CO2 is near normal, while there is hypoxia.
Dear fox making honor to the truth, emphysema is an obstructive dzs, not restrictive... COPD are emphysema and chronic bronchitis, while restrictive dzs are pulmonary fibrosis, sarcoidosis, pneumoconiosis..
There are 2 determinants of CO2 levels, metabolic rate and ALVEOLAR VENTILATION (under stable metabolic conditions alveolar ventilation is mainly determined by the respiratory rate and tidal volume), in emphysema alveolar ventilation is not as defective as in chronic bronchitis that's why pts with emphysema are not as cyanotic as the blue bloaters.. These patients may even hyperventilate but their alveoli are destroyed, since there are many defective alveoli there is a considerable decrease in the total surface of the respiratory membrane for gas exchange.. no matter how hard they breathe they can only excrete a limited amount of CO2 due to their anatomic defect..
Comments are always accepted and I hope this helps.....
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| goodyear
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Thanks mazinger!
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| fox
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Thanks for clearing a basic concept!
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| webjeee
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please explain how Dlco contribute to ventilation
In emphysema, DLco is decreased, and normal on CB. Why emphysema can get well ventilated to be a pink puffer? increase RR? in this case, patient has wheeze & ronchi, seems diffusion is compromised like in CB, will it be choice a?
Please explain, somebody.
thanks.
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