Arterial PCO2 in chronic metabolic acidosis.

The arterial blood partial pressure of carbon dioxide (PCO 2 ) falls in response to chronic metabolic acidosis, but the magnitude of the decline has differed widely between studies and types of subjects [1–9]. In general, a linear regression has been found between PCO 2 and serum bicarbonate concentration ([HCO 3 - ]), but reported values of the regression slope have varied between 0.9 [9] and 1.5 [1–4] (Table 1). The variation of the slope has never been explained. It has been suggested that the etiology of the acidosis determines the magnitude of respiratory response [8].