In patients with obesity hypoventilation syndrome, what laboratory finding is expected?

In patients with obesity hypoventilation syndrome, respiratory acidosis is the expected laboratory finding due to impaired ventilation leading to increased levels of carbon dioxide (CO2) in the blood. This condition, often characterized by obesity, results in reduced lung volumes and a decreased ability to adequately expel CO2, especially during sleep when ventilatory drive diminishes.

As a consequence, CO2 accumulates, leading to hypercapnia (elevated carbon dioxide levels) and subsequent respiratory acidosis. The body attempts to compensate for this acidotic state; however, the compensatory mechanisms, primarily through renal adjustments, may not fully correct the respiratory acidosis, especially in the acute or severe settings.

In contrast, the other potential laboratory findings associated with different conditions do not apply here. Respiratory alkalosis, which is caused by hyperventilation, and metabolic acidosis, generally associated with conditions such as lactic acidosis or renal failure, are not relevant in the context of obesity hypoventilation syndrome. Normal arterial blood gases would not be expected in this syndrome given its characteristic hypoventilation and subsequent CO2 retention. Thus, respiratory acidosis is a key indicator of this syndrome’s pathophysiology.