Common Acid-Base Disturbance Classifications

Respiratory Acid-Base Disturbances

Primary respiratory disturbances

As PaCO2 is controlled by the lung, changes in pH caused by PaCO2 are considered respiratory disturbances

Hyperventilation lowers PaCO2, which raises pH, so is referred to as respiratory alkalosis.

Hypoventilation raises PaCO2 which decreases the pH, so is called respiratory acidosis.

Disorders are identified as

Acute ventilatory failure (respiratory acidosis)

Acute ventilatory failure with partial renal compensation

Chronic ventilatory failure with complete renal compensation

Acute alveolar hyperventilation (respiratory alkalosis)

Acute alveolar hyperventilation with partial renal compensation

Chronic alveolar hyperventilation with complete renal compensation

Metabolic Acid-Base Disturbances

Primary metabolic disturbances

These disturbances involve a gain or loss of fixed acids or HCO3.

Both will appear as changes in HCO3 as changes in fixed acids will alter the amount of HCO3 used in buffering.

A decrease in HCO3 results in a metabolic acidosis.

An increase in HCO3- results in metabolic alkalosis.

Disorders are identified as:

Metabolic acidosis with partial respiratory compensation

Metabolic acidosis with complete respiratory compensation

Metabolic alkalosis with partial respiratory compensation

Metabolic alkalosis with  complete respiratory compensation

Combined Disorders

Both metabolic and respiratory acidosis

Both metabolic and respiratory alkalosis