Inadequate exhalation of carbon dioxide can cause which of the following conditions?

• A. Metabolic alkalosis
• B. Respiratory alkalosis
• C. Metabolic acidosis
• D. Respiratory acidosis

Answer: (D)

Verified step by step guidance

1. Understand the relationship between carbon dioxide (CO2) and blood pH: CO2 is transported in the blood and reacts with water to form carbonic acid (H2CO3), which dissociates into hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻). This reaction is represented as: ${\mathrm{CO}}_2+H_{2}O\leftrightarrow H_2{\mathrm{CO}}_3\leftrightarrow H_{+}+{\mathrm{HCO}}_3$. An increase in CO2 levels leads to more H⁺ ions, lowering blood pH (acidosis).
2. Identify the role of exhalation in regulating CO2 levels: During normal respiration, CO2 is exhaled, preventing its accumulation in the blood. If exhalation is inadequate, CO2 builds up, shifting the equilibrium of the reaction above to produce more H⁺ ions, causing a decrease in pH.
3. Differentiate between respiratory and metabolic causes of pH imbalance: Respiratory conditions are related to changes in CO2 levels due to lung function, while metabolic conditions involve changes in bicarbonate (HCO₃⁻) or other metabolic factors. In this case, inadequate exhalation of CO2 directly implicates a respiratory cause.
4. Define respiratory acidosis: This condition occurs when CO2 accumulates in the blood due to hypoventilation (inadequate exhalation), leading to a decrease in blood pH. It is characterized by an increase in CO2 levels (hypercapnia) and a corresponding drop in pH.
5. Conclude that the correct answer is respiratory acidosis, as it directly results from the inadequate exhalation of CO2, leading to an increase in blood acidity.