Which condition is primarily initiated by hypoventilation?

Hypoventilation leads to an increase in carbon dioxide (CO2) levels in the blood. This occurs because the respiratory rate is insufficient to remove the CO2 produced by cellular metabolism. As CO2 accumulates, it combines with water to form carbonic acid, which dissociates into hydrogen ions (H+) and bicarbonate (HCO3-). The increase in hydrogen ion concentration results in a decrease in blood pH, creating an acidic environment, which is characteristic of respiratory acidosis.

Respiratory acidosis is specifically tied to inadequate ventilation leading to CO2 retention, which explains why hypoventilation is the initiating condition. In contrast, the other conditions—respiratory alkalosis, metabolic acidosis, and metabolic alkalosis—are not directly caused by hypoventilation. Respiratory alkalosis, for instance, is caused by hyperventilation, resulting in decreased CO2 levels. Metabolic acidosis and alkalosis relate more to metabolic disturbances rather than respiratory control. Therefore, the connection between hypoventilation and the resulting increase in CO2 leading to respiratory acidosis makes this the correct answer.