Quiz 4: Blood Gasses

Question 1

Which is the most predominant buffer system in the body?

(a) Bicarbonate/carbonic acid
(b) Acetate/acetic acid
(c) Phosphate/phorphorous acid
(d) Hemoglobin

Answer 1

(a) Bicarbonate/carbonic acid

Question 2

The measurement of the pressure of dissolved CO₂ (PCO₂) in the blood is most closely associated with the concentration of what substance?

(a) pH
(b) Bicarbonate
(c) Carbonic acid
(d) PCO2

Answer 2

(c) Carbonic acid

Question 3

To maintain a pH of 7.4 in plasma, it is necessary to maintain a

(a) 10:1 ratio of bicarbonate to carbonic acid
(b) 20:1 ratio of bicarbonate to carbonic acid
(c) 1:20 ratio of bicarbonate to carbonic acid
(d) 20:1 ratio of carbonic acid to bicarbonate

Answer 3

(b) 20:1 ratio of bicarbonate to carbonic acid

Question 4

Which of the following represents the Henderson-Hasselbalch equation as applied to blood pH?

(a) pH = 6.1 + (log HCO3- / PCO2)
(b) pH = 6.1 + [log HCO3-/ (0.0306 x PCO2)]
(c) pH = 6.1 + (log DCO2 / HCO3-)
(d) pH = 6.1 + [log (0.03 x PCO2)/HCO3-]

Answer 4

(b) pH = 6.1 + [log HCO3-/ (0.0306 x PCO2)]

Question 5

What is the blood pH when the partial pressure of carbon dioxide (Pco₂) is 60 mmHg and the bicarbonate concentration is 18 millimoles per liter (mmol/L)? (Use Alpha coefficient = 0.03)

(a) 6.89
(b) 7.00
(c) 7.10
(d) 7.30

Answer 5

(c) 7.10

Question 6

Which of the following is the correct collection and handling for the analysis of blood gases?

(a) Glass syringe, liquid heparin, store on ice, assay within 15 minutes
(b) Glass syringe, no additive, store on ice, assay within 15 minutes
(c) Plastic syringe, dry lithium heparin, store on ice, assay within 1 hour
(d) Plastic syringe, dry lithium heparin, store at room temperature, assay within 15 - 20 minutes

Answer 6

(d) Plastic syringe, dry lithium heparin, store at room temperature, assay within 15 - 20 minutes

Question 7

What is the maximum recommended storage time and temperature for an arterial blood gas sample drawn in a plastic syringe?

(a) 10 min at 2 C - 8 C
(b) 20 min at 2 C - 8 C
(c) 30 min at 2 C - 8 C
(d) 30 min at 22 C

Answer 7

(c) 30 min at 2 C - 8 C

Question 8

If a blood gas specimen is left exposed to air, which of the following changes will occur?

(a) PO2 and pH increase; PCO2 decrease
(b) PO2 and pH decrease; PCO2 increase
(c) PO2 increase; pH and PCO2 decrease
(d) PO2 decreases; pH and PCO2 increase

Answer 8

(a) PO2 and pH increase; PCO2 decrease

Question 9

How would blood gas parameters change if a sealed specimen if left at room temperature for 2 or more hours?

(a) PO2 increases, PCO2 increases, pH increases
(b) PO2 decreases, PCO2 decreases, pH decreases
(c) PO2 decreases, PCO2 increases, pH decreases
(d) PO2 increases, PCO2 increases, pH decreases

Answer 9

(c) PO2 decreases, PCO2 increases, pH decreases

Question 10

In order to maintain electrical neutrality in the red blood cell, bicarbonate leaves the red blood cell and enters the plasma through an exchange mechanism with what electrolyte?

(a) Sodium
(b) Potassium
(c) Chloride
(d) Phosphate

Answer 10

(c) Chloride

Question 11

Which of the following best represents the reference intervals for arterial pH?

(a) 7.35 to 7.45
(b) 7.42 to 7.52
(c) 7.38 to 7.68
(d) 6.85 to 7.56

Answer 11

(a) 7.35 to 7.45

Question 12

Which of the following sets of blood gas data is considered within reference intervals?

(a) pH 7.33, HCO3 18 mmol/L, pCO2 32 mmHg
(b) pH 7.30, HCO3 16 mmol/L, pCO2 28 mmHg
(c) pH 7.45, HCO3 22 mmol/L, pCO2 40 mmHg
(d) pH 7.40, HCO3 25 mmol/L, pCO2 40 mmHg

Answer 12

(d) pH 7.40, HCO3 25 mmol/L, pCO2 40 mmHg

Question 13

Which of the following will cause a shift of the oxygen dissociation curve to the right, resulting in a decreased affinity of hemoglobin for O₂?

(a) Low plasma pH level
(b) Low PCO2 level
(c) Low concentration of 2,3-bisphosphoglycerate
(d) Low temperature

Answer 13

(a) Low plasma pH level

Question 14

Which of the following will shift the O₂ dissociation curve to the right decreasing oxygen affinity?

(a) Acute alkalemia
(b) Hypothermia
(c) Hypercapnia (Increased CO2 in blood)
(d) Low 2,3-DPG

Answer 14

(c) Hypercapnia (Increased CO2 in blood)

Question 15

Which of the following characterizes respiratory acidosis?

(a) Excess of bicarbonate
(b) Deficit of bicarbonate
(c) Excess of dissolved carbon dioxide (PCO2)
(d) Deficit of dissolved carbon dioxide (PCO2)

Answer 15

(c) Excess of dissolved carbon dioxide (PCO2)

Question 16

Which of the following is the primary mechanism of compensation for metabolic acidosis?

(a) Hyperventilation
(b) Release of epinephrine
(c) Aldosterone release
(d) Bicarbonate excretion

Answer 16

(a) Hyperventilation

Question 17

A mother brings her daughter, a 22-year-old medical laboratory science student, to her physician. The patient is hyperventilating and has glossy eyes. The mother explains that her daughter is scheduled to take her final course exam the next morning. The patient had been running around frantically all day in a worried state and then started to breathe heavily. Blood gases are drawn in the office with the following results:

pH = 7.58, PCO₂ = 55 mmHg, HCO₃⁻ = 18 mmol/L
What do these data indicate?
(a) Metabolic alkalosis, partially compensated
(b) Respiratory acidosis, uncompensated
(c) A dual problem of acidosis
(d) An error in one of the blood gas measurements

Answer 17

(d) An error in one of the blood gas measurements

Question 18

The presence of dyshemoglobins will cause a calculated % SO₂ result to be falsely (elevated, decreased) and a pulse oximeter % SpO₂ results to be falsely (elevated, decreased).

(a) Elevated, elevated
(b) Decreased, decreased
(c) Elevated, decreased
(d) Decreased, elevated

Answer 18

(a) Elevated, elevated

Question 19

In which circumstances will the reporting of calculated O₂ saturation of Hemoglobin based on Po₂, pH, temperature, and Hgb be in error?

(a) Carbon monoxide (CO) poisoning
(b) Diabetic ketoacidosis
(c) Oxygen therapy
(d) Assisted ventilation for respiratory failure

Answer 19

(a) Carbon monoxide (CO) poisoning

Question 20

Which of the following is true about blood gas measurements?

(a) pH and pCO2 are measured by potentiometry
(b) PO2 is measured by amperometry using a Clark electrode
(c) HCO3 and base excess calculated by instrument
(d) All of the above are true

Answer 20

(d) All of the above are true