The CO2 and HCO3 together tell you why the pH is like it is. The total range of your choices in the interpretation of blood gases is contained in the following list:

• Normal
• Respiratory Alkalosis
• Metabolic Alkalosis
• Respiratory Acidosis
• Metabolic Acidosis
• Combined Respiratory and Metabolic Alkalosis
• Combined Respiratory and Metabolic Acidosis
• Partially Compensated Respiratory Alkalosis
• Partially Compensated Metabolic Alkalosis
• Partially Compensated Respiratory Acidosis
• Partially Compensated Metabolic Acidosis
• Compensated Respiratory Alkalosis
• Compensated Metabolic Alkalosis
• Compensated Respiratory Acidosis
• Compensated Metabolic Acidosis

Lets look at some more examples:

The pH is very alkalotic at 7.70.
The CO2 is normal and is not the cause of the alkalosis.
The HCO3 is alkalotic so that the elevated HCO3 of 47 mEq is the cause :
A METABOLIC ALKALOSIS