What is the respiratory physiology of hypoventilation?

Updated: Jul 22, 2021
  • Author: Jazeela Fayyaz, DO; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
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Answer

The respiratory control system tightly regulates ventilation. Alveolar ventilation (VA) is under the control of the central respiratory centers, which are located in the ventral aspects of the pons and medulla. The control of ventilation has metabolic and voluntary neural components. The metabolic component is spontaneous and receives chemical and neural stimuli from the chest wall and lung parenchyma and receives chemical stimuli from the blood levels of carbon dioxide and oxygen.

Metabolism rapidly generates a large quantity of volatile acid (carbon dioxide) and nonvolatile acid in the body. The metabolism of fats and carbohydrates leads to the formation of a large amount of carbon dioxide, which combines with water to form carbonic acid (H2 CO3). The lungs excrete the volatile fraction via ventilation. Therefore, acid accumulation does not occur. PaCO2 is tightly maintained in a range of 39-41 mm Hg in normal states.

Ventilation is influenced and regulated by chemoreceptors for PaCO2, PaO2, and pH, located in the brainstem; by neural impulses from lung stretch receptors; and by impulses from the cerebral cortex. Failure of any of these mechanisms results in a state of hypoventilation and hypercapnia.


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