Author Question: If the PCO2 of an arterial blood sample is 60 mm Hg, the expected pH is: a. 7.20. c. 7.50. b. ... (Read 88 times)

fnuegbu · **on:** Jul 16, 2018

If the PCO2 of an arterial blood sample is 60 mm Hg, the expected pH is:

a. 7.20. c. 7.50.
b. 7.30. d. 7.60.

Question 2

Erroneous PCO2 measurements can be caused by which of the following?

1. A worn electrode
2. A cracked electrode
3. Wearing out of the silver anode
4. Increased temperature of the patient
5. Dehydration of bicarbonate solution
a. 1 and 5 c. 3 and 4
b. 2 and 3 d. 1, 2, and 5

blakeserpa · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: A
The pH changes by 0.1 unit for every 10-mm Hg increase in PCO2. Therefore, a PCO2 of 60 mm Hg is 20 mm Hg higher than normal, which equates to 2 0.1 = 0.2 decrease in pH from normal, or 7.40 0.2 = 7.20.

Answer to Question 2

ANS: D
The most common problems encountered with a PCO2 electrode involve interference with the diffusion of CO2 across the Teflon membrane and the H+ ions across the glass membrane from either worn or cracked electrodes or protein deposits. If the bicarbonate solution dehydrates be-tween the Teflon membrane and the pH glass electrode, erroneous data can result.