A previously healthy 35-year-old woman develops hypoxemia after ingesting a near-lethal dose of barbiturates. What are the expected arterial blood gas values?

In this scenario, we are examining a case of hypoxemia following a near-lethal dose of barbiturates in a previously healthy individual. Barbiturates are central nervous system depressants that can cause respiratory depression, leading to inadequate ventilation and subsequent hypoxemia.

When we analyze the expected arterial blood gas values in this situation, the partial pressure of oxygen (PO2) is expected to be lower than normal due to the hypoxemia. A value of 60 mm Hg for PO2 reflects significant hypoxemia, which aligns with the clinical scenario of respiratory depression caused by barbiturate overdose.

The partial pressure of carbon dioxide (PCO2) is typically elevated in cases of respiratory depression because the body is unable to adequately exhale carbon dioxide. A PCO2 value of 35 mm Hg indicates that the patient is likely still managing to maintain some level of respiration, but it may be borderline or slightly compromised due to the CNS depression caused by the barbiturates. Normally, respiratory acidosis would lead to an increase in PCO2, but this specific choice presents a scenario where PCO2 isn't severely elevated, possibly suggesting some compensatory mechanisms at play.

The (A-a)O2 gradient, which