What causes respiratory alkalosis?

From the Guidelines

Respiratory alkalosis is primarily caused by hyperventilation, which can be triggered by psychogenic disorders such as anxiety and hyperventilation syndrome, as evidenced by a study published in the American Journal of Respiratory and Critical Care Medicine 1. This condition leads to excessive elimination of carbon dioxide from the body, resulting in decreased carbon dioxide levels in the blood and a rise in blood pH above the normal range. Some key characteristics of hyperventilation syndrome include:

• Abnormal breathing patterns at rest and during exercise
• Impressive hyperventilation as evidenced by abnormal increases in Ve, Ve/Vco, and respiratory frequency
• Respiratory alkalosis, characterized by decreased PetCO2 and Pa CO2
• Chronic respiratory alkalosis with a downregulated Pa CO2 set point may also be observed at rest before exercise Other symptoms due to respiratory alkalosis may also be elicited, such as lightheadedness, dizziness, numbness or tingling in extremities, muscle twitching, and in severe cases, tetany or seizures. It is essential to identify hyperventilation syndrome, as appropriate treatment is usually successful 1. Treatment focuses on addressing the underlying cause, such as breathing into a paper bag for anxiety-induced hyperventilation or adjusting ventilator settings. Understanding respiratory alkalosis is crucial because it can significantly affect oxygen delivery to tissues and neurological function if left untreated.

From the Research

Causes of Respiratory Alkalosis

• Respiratory alkalosis is caused by an increase in alveolar ventilation, leading to a decrease in carbon dioxide (CO2) levels in the blood 2
• This can be due to various factors, including:
  • Pulmonary disorders 3
  • Extrapulmonary disorders 3
  • Hyperventilation syndrome, which is a common cause of respiratory alkalosis in the emergency department setting 3
  • Panic disorder, which can lead to hyperventilation and subsequent respiratory alkalosis 4, 5
  • Psychogenic hyperventilation, which can cause severe respiratory alkalosis 5
• Respiratory alkalosis can also be caused by other factors, such as:
  • Disorders that increase alveolar ventilation 6
  • Inhibition of the medullary respiratory center 6

Underlying Mechanisms

• The decrease in CO2 levels leads to an increase in blood pH, causing alkalosis 2
• The body attempts to compensate for the alkalosis by decreasing the levels of bicarbonate (HCO3-) in the blood 2
• In chronic respiratory alkalosis, the kidneys play a role in compensating for the alkalosis by decreasing the reabsorption of HCO3- 2