Deck 8: Interpretation of Blood Gases

Question 1

What is the normal value for arterial pH?

A) 7.20 to 7.30
B) 7.35 to 7.45
C) 7.45 to 7.50
D) >7.50

Answer 1

7.35 to 7.45

Question 2

An arterial puncture site normally should be compressed for a minimum of ___ min after the puncture.

A) 1 to 2
B) 3 to 5
C) 5 to 7
D) 8 to 10

Answer 2

3 to 5

Question 3

Which of the following is the most common site for arterial puncture?

A) Radial artery
B) Ulnar artery
C) Temporal artery
D) Femoral artery

Answer 3

Radial artery

Question 4

What could cause tissue hypoxia with normal arterial oxygenation?

A) Inadequate cardiac output
B) Polycythemia
C) Leukocytosis
D) Bradypnea

Question 5

Which of the following would be the best indicator of tissue oxygenation?

A) PaO₂
B) SaO₂
C) CaO₂
D) PO₂

Question 6

A shift to the right in the oxyhemoglobin dissociation curve has what effect on the affinity of hemoglobin for oxygen?

A) Increased
B) Decreased
C) No change
D) Cannot predict the change without a pH

Question 7

What is the normal value for PaO₂ in the adult patient breathing room air?

A) 50 to 60 mm Hg
B) 60 to 70 mm Hg
C) 70 to 80 mm Hg
D) 80 to 100 mm Hg

Question 8

What is the most common physiologic cause of hypoxemia in patients with lung disease?

A) Hypoventilation
B) V/Q mismatch
C) Hyperventilation
D) Diffusion defect

Question 9

A 32-year-old man comes to the emergency department after a traffic accident with the following data: pulse, 118 beats/min; respiratory rate, 27 breaths/min; blood pressure, 100/68 mm Hg; paradoxical chest movement on the left side; breath sounds decreased on the left; and ABG on room air (21%) as follows: pH, 7.32; PaCO₂, 70 mm Hg; PaO₂, 57 mm Hg; HCO₃^-, 23 mEq/L; base excess, 0; SaO₂, 86%, CaO₂, 15.2 vol%; Hb, 13.0 g/dL; P(A-a)O₂, 18 mm Hg. Based on this information, what is the primary cause of the patient's hypoxemia?

A) Overall hypoventilation
B) V/Q mismatch
C) Diffusion defect
D) Shunt

Question 10

Which of the following is a true statement regarding the term hypoxemia?

A) It occurs when the patient's PaO₂ is lower than predicted.
B) It indicates a condition in which tissue oxygenation is inadequate.
C) It is always considered a severe disorder.
D) It is independent of the age of the patient.

Question 11

The negative log of the hydrogen ion concentration is defined as which of the following?

A) PaCO₂
B) Base excess
C) Standard HCO₃^-
D) pH

Question 12

Which of the following tests is performed to check the collateral circulation of the radial artery before puncture?

A) Wilson's test
B) Perfusion scan
C) Sack's test
D) Allen's test

Question 13

What is the normal value for CaO₂?

A) 16 to 20 mL/dL
B) 12 to 16 mL/dL
C) 8 to 12 mL/dL
D) 4 to 8 mL/dL

Question 14

What is the primary method of transporting oxygen in the blood?

A) Dissolved in plasma
B) Bound to plasma proteins
C) In the form of HCO₃^-
D) Bound to hemoglobin

Question 15

Which of the following shifts the oxyhemoglobin dissociation curve to the left?

A) Increased PaCO₂
B) Decreased pH
C) Increased body temperature
D) Fetal hemoglobin

Question 16

Before an arterial blood gas (ABG) value is obtained, why should the patient's clotting parameters be evaluated?

A) They may affect the patient's PaO₂.
B) If reduced, they may hinder filling of the syringe with blood during the draw.
C) Bleeding time may be prolonged if they are abnormal.
D) They may affect the accuracy of the sample pH.

Question 17

What is often the first clinical sign that suggests the presence of hypoxemia?

A) Hypotension
B) Confusion
C) Decreased level of consciousness
D) Exertional dyspnea

Question 18

Which of the following would be best used to assess arterial oxygenation?

A) PaO₂
B) SaO₂
C) CaO₂
D) P(A-a)O₂

Question 19

What is a decrease in tissue oxygenation called?

A) Hypoxia
B) Hypoxemia
C) Hypercapnia
D) Acidosis

Question 20

For the test of collateral circulation in an Allen's test, "pinking up" of the hand is normal if it occurs within ____ s.

A) 10 to 15
B) 15 to 20
C) 20 to 25
D) 25 to 30

Question 21

What defines acidosis in a human?

A) pH <7.0
B) pH <7.25
C) pH <7.35
D) pH <7.40

Question 22

A 17-year-old man is brought into the emergency department. Vitals are as follows: pulse, 100 beats/min; respiratory rate, 4 breaths/min; and blood pressure, 100/65 mm Hg. The patient was at a party, where he was discovered by his friends to be slumped in a chair and unresponsive. ABG results are as follows: pH 7.29, PaCO₂ 68 mm Hg, HCO₃^- 29 mEq/L, BE + 1 mEq/L
The patient's acid-base status is classified as which of the following?

A) Uncompensated respiratory acidosis
B) Partially compensated respiratory acidosis
C) Compensated respiratory alkalosis
D) Uncompensated metabolic acidosis

Question 23

Which of the following is true regarding the PaO₂?

A) It is adequate.
B) It shows mild hypoxemia.
C) It shows moderate hypoxemia.
D) It shows severe hypoxemia.

Question 24

Which of the following parameters is the respiratory component of acid-base status?

A) PaCO₂
B) HCO₃^-
C) PaO₂
D) Base excess

Question 25

Which of the following could cause this patient's problem?

A) Anxiety and fear
B) Acute airway obstruction
C) Lactic acid production
D) Drug overdose

Question 26

Which of the following statements is true regarding the accuracy of the reported results?

A) The oxygen is inaccurate.
B) The pH is reported considerably higher than it should be.
C) The blood gas results are all accurate.
D) The reported pH is considerably lower than the given PaCO₂ and HCO₃^- would indicate.

Question 27

The acid-base status is classified as which of the following?

A) Uncompensated metabolic alkalosis
B) Partially compensated metabolic alkalosis
C) Uncompensated respiratory acidosis
D) Partially compensated respiratory acidosis

Question 28

An acute increase in PaCO₂ of 10 to 15 mm Hg causes a corresponding increase in plasma HCO₃^- of how many mEq/L?

A) 1
B) 2
C) 3
D) 4

Question 29

A patient has the following ABG results: pH 7.25, PaCO₂ 32 mm Hg, HCO₃^- 16 mEq/L, base excess -10 mEq/L
Based on these findings, the patient has which of the following?

A) Compensated metabolic acidosis
B) Uncompensated respiratory acidosis
C) Uncompensated metabolic acidosis
D) Compensated respiratory acidosis

Question 30

A 35-year-old, 54 kg woman with congestive heart failure enters the emergency department short of breath. An ABG shows the following results: pH 7.50, PaCO₂ 30 mm Hg, HCO₃^- 23 mEq/L, base excess +2 mEq/L
The patient's ABG results indicate which of the following?

A) Uncompensated respiratory alkalosis
B) Compensated respiratory acidosis
C) Uncompensated metabolic alkalosis
D) Uncompensated metabolic acidosis

Question 31

Which of the following is true regarding oxygen-carrying capacity?

A) It is normal.
B) It is increased.
C) It is decreased.
D) Cannot be determined with the given data.

Question 32

Which of the following ratios of HCO₃^-/PaCO₂ results in a pH of 7.40?

A) 24:1
B) 20:1
C) 15:1
D) 6:0.03

Question 33

Which of the following is a correct representation of the Henderson-Hasselbalch equation?

A) pK = pH - log (PaCO₂ $\bullet$ 0.03)/ HCO₃^-
B) pK = pH - log HCO₃^-/(PaCO₂ $\bullet$ 0.03)
C) pH = pK + log HCO₃^-/(PaCO₂ $\bullet$ 0.03)
D) -pH = pK - log HCO₃^- /(PaCO₂ $\bullet$ 0.03)

Question 34

Which of the following could cause metabolic acidosis?

A) Cardiovascular disease
B) Renal disease
C) Hypokalemia
D) Vomiting

Question 35

What is the direct effect of an increased PaCO₂ on HCO₃^-?

A) Causes it to increase.
B) Causes it to decrease.
C) Does not have any effect on it.
D) Complicated because it has an unpredictable effect on bicarbonate.

Question 36

Which of the following is the best indicator of metabolic acid-base status?

A) Plasma HCO₃^-
B) Base excess
C) Standard HCO₃^-
D) T40 HCO₃^-

Question 37

Given the following ABG results, interpret the acid-base status: pH 7.44, PaCO₂ 25 mm Hg, HCO₃^-17 mEq/L, base excess -6 mEq/L

A) Compensated metabolic acidosis
B) Uncompensated respiratory alkalosis
C) Uncompensated respiratory acidosis
D) Compensated respiratory alkalosis

Question 38

Which of the following is true regarding respiratory alkalosis?

A) The PaCO₂ is less than 35 mm Hg.
B) An increase in HCO₃^- compensates for respiratory alkalosis.
C) It is called completely compensated if the pH is 7.52.
D) It is called partially compensated if the pH is in the normal range.