q4 - okt3

[ArchivalUser]

A physician in the emergency department is evaluating a patient with severe chronic obstructive pulmonary disease
prior to oxygen supplementation. The physician decides to draw arterial blood for blood gas studies. His technique
is faulty, however, and he introduces room air into the syringe while pulling on the plunger as he is drawing the
syringe out of the patient. Which of the following patterns of changes would be most likely to be produced by this
exposure of arterial blood to room air?



PO2
PCO2
pH

A. Decreased
Decreased
Decreased

B. Decreased
Elevated
Decreased

C. Elevated
Decreased
Decreased

D. Elevated
Decreased
Elevated

E. Elevated
Elevated
Elevated

[ArchivalUser]

D?

[ArchivalUser]

B?

[ArchivalUser]

The correct answer is D. The technical part of the collection of arterial blood samples is difficult. Some hospitals
allow only physicians to collect the samples, while other hospitals allow nurses or technicians with additional
special training to collect the samples. No matter who performs the arterial draw, care must be taken to avoid
exposing the blood to room air, as such exposure tends to cause the blood to partially equilibrate with the room
air. Room air would have a higher PO2 and a lower PCO2 than this patient's blood, so the sample would have a
higher PO2 and a lower PCO2. In the atmosphere, PO2 = 150 mm Hg and PCO2 is near 0 mm Hg; in the arterial
blood of a healthy patient, PO2 = 100 mm Hg, PCO2 = 40 mm Hg (PO2 could be lower and PCO2 higher in a
diseased individual). Because CO2 is decreased, there will be less carbonic acid present in the blood, thus
raising the pH.

[ArchivalUser]

dd

[ArchivalUser]

oh ! u already gave it!