section name header

Table 37.2

Classification and Examples of Acid-Base Disorders According to Arterial Hydrogen Ion Concentration/pH and PCO2 (Figure 37.1)

Arterial hydrogen ion concentration (nmol/L) or pH
Arterial PCO2 (kPa)

[H+] >45

pH < 7.35

35–45

7.35–7.45

<35

>7.45

<4.7

Metabolic acidosis with partial respiratory compensation or

Metabolic acidosis plus respiratory alkalosis, for example:

Respiratory alkalosis with metabolic compensation

Respiratory alkalosis or

Respiratory alkalosis plus

metabolic alkalosis, for example:

4.7–6.0

Metabolic acidosis

Normal acid-base status

Metabolic alkalosis

>6.0

Respiratory acidosis or

Respiratory acidosis plus metabolic acidosis, for example:

  • Cardiopulmonary arrest
  • COPD complicated by circulatory failure or sepsis
  • Severe pulmonary oedema
  • Combined respiratory and renal failure
  • Severe tricyclic poisoning

Respiratory acidosis with metabolic compensation, for example:

  • COPD with chronic CO2 retention

Metabolic alkalosis plus respiratory acidosis, for example:

  • Diuretic therapy plus COPD with chronic CO2 retention

COPD, chronic obstructive pulmonary disease.