Why does cardiac output sometimes fall during an asthma exacerbation, even if the heart is healthy?

💡 Explanation

Cardiac output declines because increased airway resistance during asthma leads to alveolar hypoxia and hypoxic pulmonary vasoconstriction; this increases pulmonary vascular resistance, increasing the heart's afterload. Therefore, the heart struggles to pump blood, rather than a direct myocardial problem or systemic vasodilation.

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