Respiratory acidosis and alkalosis are associated with compensatory physiological changes, including extracellular and intracellular buffering, and altered renal ion handling. In clinical practice, mixed acid-base disturbances may be misdiagnosed if the expected magnitude of compensation for a primary respiratory disorder is not known.

The ability to assess physiological compensation rapidly for acid-base disorders can be achieved either through intuition gained after many years of clinical experience, by use of a graph or nomogram,1 or through the application of one of the published formulae for predicting compensation.2 3 However, nomograms are often not readily available in clinical environments, and the most accurate formulae are complex and difficult to memorise reliably.

A comprehensive summary of previously published measurements of metabolic compensation …