Acid-Base Physiology

4.3 Respiratory Acidosis - Maintenance

Key Fact: A rise in arterial pCO2 is a potent stimulus to ventilation so a respiratory acidosis will rapidly correct unless some abnormal factor is maintaining the hypoventilation.

This feedback mechanism is responsible for the normal tight control of arterial pCO2. The factor causing the disorder is also the factor maintaining it. The prevailing arterial pCO2 represents the balance between the effects of the primary cause and the respiratory stimulation due to the increased pCO2.

Other then by ventilatory assistance, the pCO2 will return to normal only by correction of the cause of the decreased alveolar ventilation.

An extremely high arterial pCO2 has direct anaesthetic effects and this will lead to a worsening of the situation either by central depression of ventilation or as a result of loss of airway patency or protection.