What happens to alveolar oxygen partial pressure (PAO₂) and arterial oxygenation if V/Q mismatch causes negligible ventilation but maintained perfusion in a lung region?
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Correct answer: PAO₂ falls toward venous levels, arterial oxygenation decreases
If ventilation drops but perfusion remains, alveolar gas equilibrates with poorly oxygenated blood, causing low PAO₂ and decreased arterial oxygen — similar to a physiological shunt.
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