A critically ill patient has the following arterial blood gas. What acid-base disturbance is occurring? pH = 7.27 PCO2 = 54 mmHg, pO2 = 78 mmHg, HCO3 = 27 mEq/L a-Metabolic acidosis b-Metabolic alkalosis c-Respiratory alkalosis d-Respiratory acidosis e-There is no acid-base disorder