pCO2 is a measure of tension or pressure of carbon dioxide dissolved in the blood. The pCO2 of blood represents the balance between cellular production of CO2 and ventilatory removal of CO2. A normal, steady pCO2 indicates that the lungs are removing CO2 at about same rate as tissues producing CO2. A change on pCO2 indicates an alteration in this balance, usually due to the change in ventilatory status.
Normal range:
Arterial: 35 " “45 mm Hg
Venous: 41 " “51 mm Hg
Interpretation
Increased In
Acute respiratory acidosis
Depression of respiratory center
Suppressed neuromuscular system
Pulmonary disorders
Inadequate mechanical ventilation
Chronic respiratory acidosis
Decreased alveolar ventilation
Hypoventilation
Compensation in metabolic alkalosis
Decreased In
Respiratory alkalosis
Increased stimulation of respiratory center
Hypermetabolic states
Mechanical hyperventilation
Compensation in metabolic acidosis
Limitations
Respiratory conditions will primarily affect pCO2, whereas metabolic disturbances are first reflected in the HCO3 ¢ ˆ ’.
Values are slightly lower in supine position.
Difference between arterial blood and venous blood varies considerably, depending on the skin temperature, length of stasis, and muscular activity.