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.

• Why does chronic hypertension, despite adequate arterial baroreceptor signaling, often necessitate multiple drug therapies including aldosterone antagonists?
• An endurance athlete's cardiac output increases substantially during exercise. What distinguishes the mechanism enabling this increased output from the response in someone with advanced heart failure?
• A patient with cirrhosis experiences significantly reduced liver glycogen stores. Which outcome is most likely given this constraint on liver function?
• If a woman experiences consistently short luteal phases due to inadequate progesterone secretion after ovulation, what consequence becomes most likely, assuming normal follicle development and fertilization?
• If a patient presents with severe dehydration following prolonged exertion, which consequence related to the renin-angiotensin-aldosterone system (RAAS) and antidiuretic hormone (ADH) is most likely?
• A patient with cystic fibrosis exhibits abnormally thick sebum production affecting their skin's antimicrobial defense. Which mechanism best explains why their skin becomes more susceptible to bacterial infections?