Why does the brainstem trigger increased respiration when the ventilation-perfusion ratio decreases significantly in a lung region affected by localized pneumonia?

💡 Explanation

Decreased ventilation relative to perfusion indicates that blood is passing through poorly ventilated alveoli and not adequately picking up oxygen; because the brainstem senses decreased arterial oxygen, it increases respiration to attempt to improve overall systemic oxygenation and compensate for systemic hypoxemia, rather than focusing solely on the poorly ventilated region. Therefore, it is systemic compensation, rather than localized adjustment.

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