1. Abnormally slow and shallow respiration, resulting in an increased level of carbon dioxide in the blood: Hypoventilation can result due to a medical condition, by a drug overdose, or even by holding one's breath!
2. A condition in which there is a reduced amount of air entering the pulmonary (lung) alveoli (small cell containing air in the lungs), causing decreased levels of oxygen and increased levels of carbon dioxide in the blood Hypoventilation can be a result of breathing that is too shallow (hypopnea), or too slow (bradypnea), or by diminished lung function.