Respiratory Acidosis
A ventilation-perfusion inequality: Whenever PaCO2 is increased, the bicarbonate concentration also rises, due to dissociation of carbonic acid. A pH less than 7.35, with a PaCO2 greater than 45 mm/Hg. The acid state occurs when an accumulation of PaCO2 combines with water to produce carbonic acid, which lowers blood pH. Hypoventilation can lead to Respiratory Acidosis, and an increase in ventilation may correct the problem.

Cardiovascular Tachycardia, Dysrhythmias
Neurological Confusion, Headache, Restlessness
Pulmonary Dyspnoea, Respiratory distress, Shallo breathing

Arterial blood gas example: Compensated Respiratory Acidosis: if PaCO2 indicates acidosis, and HCO3 indicates alkalosis, and pH is normal, but less than 7.4.