The medullary respiratory center controls the depth and rate of respiration based on input from central and peripheral chemoreceptors and airway mechanoreceptors:

PaCO2 is the major stimulator of respiration in healthy people. Even a slight increase in PaCO2 results in increased pulmonary ventilation.

In patients with COPD, response to PaCO2 is blunted and hypoxemia becomes an important contributor to the respiratory drive. Peripheral chemoreceptors are primarily responsible for sensing arterial PaO2 and can be suppressed with oxygen administration.