Simple, easily memorised "rules of thumb" for the rapid assessment of physiological compensation for respiratory acid-base disorders.

Respiratory acidosis and alkalosis are associated with compensatory physiological changes, including extracellular and intracellular buffering, and altered renal ion handling. In clinical practice, mixed acidbase 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, or through the application of one of the published formulae for predicting compensation. 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 for respiratory disorders was recently published. Using these data, simple but accurate ‘‘rules of thumb’’ for the assessment of physiological compensation for respiratory disorders are developed here.