A patient with pneumonia presents with a pH of 6.9 and PCO2 of 52 mmHg. What acid-base disorder is this indicative of?

A pH of 6.9 indicates significant acidosis, as the normal range for arterial blood pH is approximately 7.35 to 7.45. The elevated PCO2 of 52 mmHg suggests that the patient is retaining carbon dioxide, which is a hallmark of respiratory acidosis. In respiratory acidosis, the primary problem is an excess of carbon dioxide in the bloodstream due to inadequate ventilation, leading to an increase in hydrogen ion concentration and a decrease in pH.

In this scenario, the patient's pneumonia can cause airway obstruction or reduced lung function, resulting in impaired gas exchange. As the lungs cannot expel carbon dioxide effectively, its concentration rises, contributing to the acid-base disturbance. The combination of a low pH and high PCO2 confirms that this is a case of respiratory acidosis, particularly when the metabolic system has not yet compensated by altering bicarbonate levels.

The other possible options present different acid-base disorders that do not fit the data provided: metabolic alkalosis typically presents with a high pH and increased bicarbonate levels; metabolic acidosis involves a low pH with either a low bicarbonate concentration or an elevated anion gap; uncompensated respiratory alkalosis would show a high pH along with low