Scenario A: Bill is a marathoner and is half way through the New York marathon.

Question

Scenario A: Bill is a marathoner and is half way through the New York marathon. His legs (and some other muscles) are burning huge amounts of ATP (total metabolic rate has increased to around 7 times basal). His cardiac output has risen to five times the basal rate. His respiratory rate has increased from 10 breath/min at rest to about 20 breath/min. His tidal volume has risen from 700 ml at rest to about 1525 ml. He weighs about 70 kg (~150 lb). If no other control actions or reflexes occur, what will be the effect on _______ (compared to rest values)
48) PO2 at the alveoli:

a) increased by 30 mmHg, b) largely unchanged, c) decreased by 30 mmHg

49) PO2 at the left atrium:

a) increased by 30 mmHg, b) largely unchanged, c) decreased by 30 mmHg

50) PO2 at the right ventricle (mixed venous PO ):

a) increased by 10 mmHg, b) largely unchanged, c) decreased by 10 mmHg

51) Oxygen delivery to the systemic tissues

a) decreased by 20% b) largely unchanged c) increased by 20% d) increased proportionally to increase in cardiac output e) increased proportionally to increase in metabolism

Explanation / Answer

48) PO2 at the alveoli:

The correct statement is .................a) increased by 30 mmHg

Alveolar oxygen = inspired oxygen - oxygen consumed

a) increased by 30 mmHg, b) largely unchanged, c) decreased by 30 mmHg

49) PO2 at the left atrium:

The correct statement is...............a) increased by 30 mmHg

a) increased by 30 mmHg, b) largely unchanged, c) decreased by 30 mmHg

50) PO2 at the right ventricle (mixed venous PO ):

The correct statement is...............c) decreased by 10 mmHg

a) increased by 10 mmHg, b) largely unchanged, c) decreased by 10 mmHg

51) Oxygen delivery to the systemic tissues

The correct statement is...............d) increased proportionally to increase in cardiac output

a) decreased by 20% b) largely unchanged c) increased by 20% d) increased proportionally to increase in cardiac output e) increased proportionally to increase in metabolism

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