pH: 7.40
PaCO2: 56
HCO3: 34

How is there any way to know if this is metabolic alkalosis or respiratory acidosis (fully compensated). In the case of other fully compensated problems I've done the pH has been either on the lower end of 7.35-7.45 or the higher end of 7.35-7.45 and that's how I would determine if the original disturbance was acidosis or alkalosis. How do you determine it when it's exactly 7.40?