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How does hypoventilation change oxygen and carbon dioxide levels in the blood?

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Medical illustration of the human chest showing the lungs, diaphragm, ribs, trachea, bronchus, and bronchioles, with one lung cut away to reveal internal structures. — human respiratory system The lungs serve as the gas-exchanging organ for the process of respiration.

Hypoventilation occurs when the quantity of inspired air entering the lungs is insufficient to maintain normal gas exchange. This condition leads to a reciprocal change in blood gas levels: the partial pressure of carbon dioxide in the blood rises, while the partial pressure of oxygen falls.1

Because the composition of alveolar gas directly determines the gas partial pressures in the blood perfusing the lungs, these changes occur in parallel within the arterial blood. Notably, hypoventilation is the only category of abnormal gas exchange that does not increase the difference between arterial and alveolar partial pressures of oxygen.1