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Respiratory Alkalosis

Respiratory alkalosis results from alveolar hyperventilation. It's marked by a decrease in partial pressure of arterial carbon dioxide (paco2) (less than 35 mm Hg) and an increase in blood pH over 7.45. Uncomplicated respiratory alkalosis leads to a decrease in hydrogen ion concentration, which raises the blood pH. Hypocapnia occurs when the lungs eliminate more carbon dioxide (CO2) than the body produces at the cellular level. In the acute stage, respiratory alkalosis is also called hyperventilation syndrome.


Predisposing conditions to respiratory alkalosis include:

  • heart failure
  • central nervous system (CNS) injury to the respiratory control center
  • extreme anxiety
  • fever
  • overventilation during mechanical ventilation
  • pulmonary embolism
  • salicylate intoxication (early).

Signs and Symptoms

Common causes include hyperventilation, anxiety, and fever.

Any lung disease that leads to shortness of breath may also result in respiratory alkalosis.

Diagnostic tests

Arterial blood gas (ABG) analysis confirms respiratory alkalosis and rules out compensation for metabolic acidosis. Paco2 falls below 35 mm Hg; blood pH increases in proportion to a decrease in Paco2 in the acute stage but drops toward normal in the chronic stage. The bicarbonate level is normal in the acute stage but below normal in the chronic stage.

Serum electrolyte studies detect metabolic acidbase disorders.


In respiratory alkalosis, the goal of treatment is to eradicate the underlying condition; for example, by removing ingested toxins or by treating fever, sepsis, or CNS disease. In severe respiratory alkalosis, the patient may need to breathe into a paper bag, which helps relieve acute anxiety and increased CO2 levels. Sedatives may also be necessary. If respiratory alkalosis results from anxiety, sedatives and tranquilizers may help the patient.

To prevent hyperventilation in patients receiving mechanical ventilation. ABG levels are monitored and dead-space or minute ventilation volume is adjusted.

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