Figure 41-3 Acid-base nomogram using the Copenhagen approach as revised by Schlichtig. The various acid-base disturbances can be distinguished based on PCO₂ and base deficit or excess, here referred to as standard base excess (SBE). Arrows represent changes as the body compensates for acute acidosis or alkalosis. AR, acute respiratory acidosis or alkalosis; CR, chronic respiratory acidosis or alkalosis; M, metabolic acidosis or alkalosis. (From Schlichtig R, Grogono AW, Severinghaus JW: Human PaCO₂ and standard base excess compensation for acid-base imbalance. Crit Care Med 26: 1173–1179, 1998.)