Chapter 7, Problem 1RQ

During acute alveolar hypoventilation, the blood

1. ${\text{H}}_{\text{2}}{\text{CO}}_{\text{3}}$ increases

2. pH increases

3. ${\text{HCO}}_{\text{3}}{}^{\text{−}}$ increases

4. ${\text{P}}_{{\text{co}}_{\text{2}}}$ increases

A. 2 only

B. 4 only

C. 2 and 3 only

D. 1,3, and 4 only

Summary Introduction

Introduction:

Acute alveolar hyperventilation is defined as the decrease in the partial pressure of carbon dioxide due to excessive ventilation. It is of two types, that is, acute and chronic. In acute alveolar hyperventilation, the ventilation increases out of proportion to carbon dioxide production.

Answer to Problem 1RQ

Correct answer:

During acute alveolar hypoventilation, the levels of carbonic acid (${\text{H}}_{\text{2}}{\text{CO}}_{\text{3}}$), bicarbonate ions (${\text{HCO}}_{\text{3}}^{-}$), and the partial pressure of carbon dioxide (${\text{P}}_{\text{co2}}$) in the blood increase.

Explanation of Solution

Justification/explanation for the correct answer:

Option (D) states that the levels carbonic acid, bicarbonate ions, and the partial pressure of carbon dioxide increase during acute alveolar hypoventilation. Acute alveolar hypoventilation is defined as the increase in the partial pressure of carbon dioxide due to insufficient ventilation. This results an increase in carbonic acid ${\text{H}}_{\text{2}}{\text{CO}}_{\text{3}}$, bicarbonate ions ${\text{HCO}}_{\text{3}}^{-}$, and the partial pressure of carbon dioxide ${\text{P}}_{\text{co2}}$. Hence, option (D) is correct.

Explanation for the incorrect answers:

Option (A) states that during acute alveolar hypoventilation, the pH (potential of hydrogen) increases. This is incorrect because the pH does not increase in acute alveolar hypoventilation. It rather decreases due to the accumulation of bicarbonate ions. So, it is an incorrect option.

Option (B) states that during acute alveolar hypoventilation, only the ${\text{P}}_{\text{co2}}$ increases. But in reality, the levels of carbonic acid (${\text{H}}_{\text{2}}{\text{CO}}_{\text{3}}$) and bicarbonate ions (${\text{HCO}}_{\text{3}}^{-}$) increase during acute alveolar hypoventilation along with the ${\text{P}}_{\text{co2}}$. So, it is an incorrect option.

Option (C) states that during acute alveolar hypoventilation, the pH increases and the concentration of bicarbonate ions ${\text{HCO}}_{\text{3}}^{-}$ increases. This is incorrect because pH does not increase during acute alveolar hypoventilation. So, it is an incorrect option.

Hence, options (A), (B), and (C) are incorrect.

Conclusion

Therefore, it is concluded that during acute alveolar hypoventilation, the levels of carbonic acid (${\text{H}}_{\text{2}}{\text{CO}}_{\text{3}}$), bicarbonate ions (${\text{HCO}}_{\text{3}}^{-}$) and the partial pressure of carbon dioxide (${\text{P}}_{\text{co2}}$) increase.