hypoventilation /-ven′tilā″shən/ [Gk, hypo + L, ventilare, to fan] , an abnormal condition of the respiratory system that occurs when the volume of air that enters the alveoli and takes part in gas exchange is not adequate for the body’s metabolic needs. It is characterized by cyanosis, polycythemia, increased PaCO2, and generalized decreased respiratory function. Hypoventilation may be caused by an uneven distribution of inspired air (as in bronchitis), obesity, neuromuscular or skeletal disease affecting the thorax, decreased response of the respiratory center to carbon dioxide, or a reduced amount of functional lung tissue, as in atelectasis, emphysema, and pleural effusion. The results of hypoventilation are hypoxia, hypercapnia, pulmonary hypertension with cor pulmonale, and respiratory acidosis. Treatment includes weight reduction in cases of obesity, artificial respiration, and possibly tracheostomy. Compare hyperventilation. See also respiratory center.
