What does increased CO2 do to blood?

As levels of CO2 in the blood begin to rise, the body can respond through hyperventilation or hypoventilation, respectively. 

The CO2 that is bound to hemoglobin forms a carbamino compound. In circumstances where the CO2 and H+ concentrations are high, the affinity of hemoglobin for O2 is decreased.

Second, carbon dioxide can bind to plasma proteins or can enter red blood cells and bind to hemoglobin.

This form transports about 10 percent of the carbon dioxide. 

When carbon dioxide binds to hemoglobin, a molecule called carbaminohemoglobin is formed. Binding of carbon dioxide to hemoglobin is reversible.

Hypercapnia occurs when oxygen and CO2 levels become imbalanced in the bloodstream. This imbalance changes the pH balance of your blood, making it too acidic. This condition is called metabolic acidosis. Metabolic acidosis can put excess strain on the kidneys, which can lead to kidney disease or failure. Mar 3, 2023

Carbon dioxide (CO2) has a profound and reversible effect on cerebral blood flow, such that hypercapnia causes marked dilation of cerebral arteries and arterioles and increased blood flow, whereas hypocapnia causes constriction and decreased blood flow [167,168].