Question 1

What is the significance of the straight CO₂ equilibrium curve versus the sigmoid-shaped HbO₂ curve? A) A change in alveolar ventilation is much more effective in changing arterial CO₂ content than O₂ content. B) A change in alveolar ventilation is much more effective in changing arterial O₂ content than CO₂ content. C) Patients with hypercapnia have a straight HbO₂ curve. D) Patients with hypercapnia have a significant increase in O₂ release to the tissues.

Accepted Answer

It is important to note that the CO₂ dissociation curve is essentially a straight line over the physiological range (see Figure 9-6), in contrast to the sigmoid-shaped oxygen-hemoglobin dissociation curve (see Chapter 8). This meAnswer that a change in alveolar ventilation is much more effective in changing arterial CO₂ content than O₂content.

Question 2

Which of the following are major forms of carbon dioxide transport?
I.Internal metabolism
II.Dissolved CO₂ in plasma
III.Plasma HCO₃^-
IV.Protein carbamino compounds

A) II, III, IV
B) I, II, III, IV
C) II, IV
D) I, II, III

Accepted Answer

CO₂ is carried in the following three major forms in the plasma and erythrocyte: (1) dissolved CO₂ in the plasma, (2) plasma HCO₃^- and (3) protein compounds (carbamino compounds).

Question 3

Which of the following mechanisms is responsible for maintaining a normal PaCO₂ near 40 mm Hg during heavy exercise? A) A normally increases such that it eliminates CO₂ at a rate proportional to its production. B) A normally increases such that it increases O₂ at a rate proportional to CO₂ production. C) A normally increases such that it eliminates CO₂ without increasing its production. D) A normally remains stable such that CO₂ elimination is proportional to its production.

Accepted Answer

During heavy exercise, $ \dot{v} $ A normally increases such that it eliminates CO₂ at a rate proportional to its production; this maintains the PaCO₂ near 40 mm Hg and thus maintains normal blood acid (H₂CO₃) levels.

Question 4

The majority of CO₂ is transported in which of the following forms? A) Plasma HCO₃^- B) RBC HCO₃^- C) Plasma H₂CO₃ D) RBC H₂CO₃

Accepted Answer

The majority of CO₂ is trAnswerported from the tissues to the lungs in the form of plasma HCO₃^-, most of which is generated in the erythrocyte.

Question 5

Which of the following statements are true of CO₂?
I.Most CO₂ diffusing into the blood from tissue cells enters the erythrocyte.
II.The rate of reaction between CO₂ and H₂O in the RBC is quite slow.
III.The amount of CO₂ carried as H₂CO₃ in the RBC is quite small.
IV.The rate of reaction between CO₂ and H₂O in the RBC is quite fast.

A) II, III, IV
B) I, II, III, IV
C) I, IV
D) I, II, III

Accepted Answer

The reaction between CO₂ and H₂O occurs approximately 13,000 times faster in the erythrocyte than in the plasma because of the intracellular enzyme carbonic anhydrase. Thus, when CO₂ enters the RBC, it is instantly converted into H₂CO₃ and its products, bicarbonate and H?. An extremely small amount remains dissolved in the erythrocyte fluid.

Question 6

What is the average tissue-blood CO₂ gradient? A) 6 mm Hg B) 10 mm Hg C) 15 mm Hg D) 30 mm Hg

Accepted Answer

Normally, a steady state exists in which blood flow removes CO₂ at the same rate that tissues produce it, maintaining an average tissue PCO₂ of approximately 46 mm Hg. This creates an average carbon dioxide diffusion gradient between tissues and arterial blood of approximately 6 mm Hg, causing carbon dioxide to enter the capillary (tissue PCO₂ = 46 mm Hg and blood PCO₂ = 40 mm Hg).

Question 7

What is the approximate percentage of dissolved CO₂? A) 8% B) 12% C) 80% D) 100%

Accepted Answer

Dissolved CO₂ is responsible for 8% of CO₂'s transport.

Question 8

The affinity of hemoglobin for CO₂ is greater when it is not combined with oxygen.What is the name of this phenomenon? A) Bohr effect B) Haldane effect C) Fick effect D) Reynold effect

Accepted Answer

The affinity of hemoglobin for CO₂ is greater when it is not combined with oxygen, a phenomenon known as the Haldane effect. The presence of oxygen on the heme portion somewhat hinders carbaminohemoglobin formation.

Question 9

Although CO₂ is technically not an acid, what is the reason for CO₂ being conceptualized as though it were an acid? A) Its high affinity for acids in solution B) Its immediate formation of H₂CO₃^- in physiological fluids C) Its release in circulation as a volatile acid D) Its counteraction of HCO₃^- formation

Accepted Answer

Although CO₂ is technically not an acid, its immediate formation of H₂CO₃ in physiological fluids allows it to be conceptualized as though it were an acid.

Question 10

Which of the following statements are true of dissolved CO₂?
I.The rate of reaction between CO₂ and H₂O in the plasma is quite slow.
II.The amount of CO₂ carried as H₂CO₃ in the plasma is quite small.
III.The amount of H₂CO₃ in the plasma is a major determinant of the blood's H⁺ concentration (pH).
IV.The amount of H₂CO₃ in the plasma is not an important determinant of the blood's H⁺concentration (pH).

A) II, III, IV
B) I, II, III, IV
C) II, IV
D) I, II, III

Accepted Answer

The rate of this reaction is quite slow in the plasma because H₂CO₃ accumulates, slowing the reaction's movement to the right. Moreover, no enzyme is present in the plasma, as it is in the erythrocyte, to catalyze and speed up the reaction. Therefore, the amount of CO₂ carried as H₂CO₃ in the plasma is quite small. Small as it is, the amount of H₂CO₃ in the plasma is a major determinant of the blood's H⁺ concentration (pH). Because dissolved CO₂ determines the concentration of plasma H₂CO₃, dissolved CO₂ plays a key role in determining the blood pH.

Question 11

Which of the following is the best explanation for the chloride shift? A) HCO₃^- diffuses out of the RBC and leaves the cell electropositive. B) Cl^- has a strong affinity for HCO₃^-. C) HCO₃^- diffuses into the RBC and keeps the cell electronegative. D) Cl^- has no affinity for HCO₃^-.

Accepted Answer

The answer of Which of the following is the best...

Question 12

What is the approximate percentage of CO₂ transported as HCO₃^-? A) 8% B) 12% C) 80% D) 100%

Accepted Answer

The answer of What is the approximate percentage of CO₂...

Question 13

What is the average amount of CO₂ produced by the body at rest? A) 100 mL/min B) 200 mL/min C) 250 mL/min D) 300 mL/min

Accepted Answer

The answer of What is the average amount of CO₂...

Question 14

During cardiac resuscitation a 63-year-old man receives sodium bicarbonate for a profound metabolic acidosis.Why should the respiratory therapist increase ventilation at this point? A) To eliminate the additional CO₂ generated by lactic acid buffering. B) To counteract the effect of the sodium bicarbonate on the pH. C) To eliminate the additional CO₂ generated by increased hydrogen ion production. D) To counteract the effect of the sodium bicarbonate on the lactic acid.

Accepted Answer

The answer of During cardiac resuscitation a 63-year-old man receives...

Question 15

Which of the following statements explain the alkalemia that develops at high altitudes?
I.Lack of oxygen at high altitudes creates a chemical stimulus for ventilation.
II.Increased ventilation drives the PACO₂ and PaCO₂below 40 mm Hg.
III.Low PaCO₂ lowers the blood H₂CO₃concentration.
IV.Low PaCO₂ lowers PaO₂ and promotes buffer release.

A) I, II, III
B) III, IV
C) I, II, III, IV
D) II, IV

Accepted Answer

The answer of Which of the following statements explain the...

Deck 9: Carbon Dioxide Equilibrium and Transport