If metabolic acidosis is present, a delta gap is calculated to identify concomitant metabolic alkalosis, and Winters formula is applied to determine whether respiratory compensation is appropriate or reflects a second acid-base disorder (predicted P co 2 = 1.5 [HCO 3 −] + 8 ± 2; if P co 2 is higher, there is also a primary respiratory acidosis—if lower, respiratory alkalosis).