What do peripheral chemoreceptors respond to primarily?

Peripheral chemoreceptors primarily respond to oxygen levels, particularly the partial pressure of oxygen in the arterial blood. These receptors are located in the carotid bodies and the aortic bodies, where they detect changes in blood oxygen levels and play a critical role in regulating respiratory drive. When oxygen levels decline, such as during hypoxemia, peripheral chemoreceptors stimulate an increase in ventilation to improve oxygen uptake. Although these chemoreceptors also respond to carbon dioxide levels and pH changes to some extent, their primary role is in sensing oxygen levels in the blood, making this response essential for maintaining adequate oxygenation of tissues.