Partial Pressure of Carbon Dioxide (pCO2), Blood

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.