A portion of each tidal volume remains in the non-gas-exchange area of the respiratory system—termed the "dead space"—and is usually fixed by the anatomic size of the conducting airways (trachea and bronchi). The portion of the tidal volume that reaches the alveoli is that which remains after the dead space volume is subtracted: Ta = TV - Td. Alveolar ventilation per minute is the volume multiplied by the rate: A = Ta * R = (TV - Td) * R. Alveolar hypoventilation can result from a decrease in respiratory rate, a decrease in tidal volume, or an increase in dead space.
Since the medullary chemoreceptors stimulate both respiratory rate and tidal volume in response to increased CO 2, alveolar ventilation is finely controlled to maintain Paco2 within a narrow range under most circumstances. In essence, alveolar ventilation is balanced relative to the production of CO 2 to maintain the Paco2 within a narrow range. Decreased respiratory drive is associated with CNS lesions and toxic depression ( Tabl§„„5.8.-.2). Thoracic cage and neuromuscular disorders produce hypoventilation by allowing a slower respiratory rate and/or a decreased tidal volume relative to the production of CO 2. Intrinsic lung diseases, such as COPD, produce alveolar hypoventilation due to an increase in dead space.
Was this article helpful?
Deal With Your Pain, Lead A Wonderful Life An Live Like A 'Normal' Person. Before I really start telling you anything about me or finding out anything about you, I want you to know that I sympathize with you. Not only is it one of the most painful experiences to have backpain. Not only is it the number one excuse for employees not coming into work. But perhaps just as significantly, it is something that I suffered from for years.