HypoxiarAcidosis, and Hypercapnia Are All Potent Stimuli for Ventilation

Chemoreceptors monitor oxygen, carbon dioxide, and hydro­gen ion concentration (pH) at several sites in the body and provide some tonic drive to respiration during normal breath­ing. As blood composition departs from normal, small changes in arterial carbon dioxide tension (Paco₂) and pH produce major changes in ventilation, whereas hypoxemia has little effect on ventilation until the decrease in arterial oxygen tension (Pao₂) is large.