What acid-base disorder is indicated by an arterial pH of 7.05?

• A. Metabolic acidosis
• B. Metabolic alkalosis
• C. Respiratory acidosis
• D. Respiratory alkalosis

Answer: (A)

A pH of 7.05 shows acidemia, meaning the blood is too acidic. To identify the specific disorder we distinguish between metabolic and respiratory causes: metabolic changes alter bicarbonate (HCO3−), while respiratory changes alter carbon dioxide (PaCO2). To decide which is primary you’d normally look at ABG values for PaCO2 and HCO3−, because the same pH value can be due to either a metabolic or a respiratory problem depending on those numbers.

Among the given options, a pH this low fits an acidosis. Metabolic acidosis is a common cause of significant acidemia and occurs when bicarbonate is lost or when acids accumulate (as in renal failure, lactic acidosis, sepsis, or diarrhea). It typically prompts the body to compensate by increasing ventilation to blow off CO2, lowering PaCO2 on the ABG if compensation is present. Respiratory acidosis would require a high PaCO2, while metabolic alkalosis or respiratory alkalosis would present with alkalemia (pH above 7.45), which is not the case here.

So, given the pH is severely acidemic and the available option set, metabolic acidosis is the most fitting choice, with the caveat that confirmation would come from the accompanying PaCO2 and HCO3− values.