Q: According to Harrison's Int. Medicine 14e, Page 278: In met. alka., expected PaCO2=HCO3+15, which is quite different from the formula used in the ABG program: Exp. PaCO2=0.9*HCO3+9. I think the the formula in the program should be PaCO2=0.9*HCO3+ 19.

A: There are many different formulas out there. They are all just estimates. My sources are listed within the program help file.