in carbon dioxide in your red blood cells, which causes in pH, causes your breathing to speed up. See Concept 42.6 (Page) View Available Hint(s) in carbon dioxide in your red blood cells, which causes in pH, causes your breathing to speed up. See Concept 42.6 (Page) A decrease ... a drop An increase ... a rise An increase ... a drop A decrease ... a rise Actually, it is the rise and fall of oxygen, not carbon dioxide, that controls breathing.