ABG Compensation and Mixed Disorders

A normal pH does not mean a normal patient. A client can hold a pH of 7.37 while their carbon dioxide sits at 68 mmHg and their bicarbonate at 38 mmol/L — every individual number is abnormal, the pH is not, and the patient is one chest infection away from decompensating. Compensation is the body's second buffer system stepping in to drag the pH back toward normal. Reading it tells you two things a single value cannot: how long this has been going on, and how much reserve is left. That is why exam items and real handovers ask for the degree of compensation, not just the disorder name. You should already be able to read pH, PaCO₂ and HCO₃⁻ in order and name the four primary patterns. If not, complete ABG Foundations and Rapid Interpretation first — none of that material is repeated here.