Question

Ms. Y has suddenly experienced a substantial loss of endurance capacity. Six months ago, she was a good runner and swimmer, capable of exercising for hours, yet now she can only exercise for a few minutes before tiring.

As the local physiology expert, you are called in to help the M.D. diagnose the problem.

Her red blood cell count and hemoglobin levels are normal. What problems do these results eliminate? 1 pt

Heart rate is normal at rest, but goes to a very high level (near 200 beats per min) even with mild exercise.

First, you must determine whether the primary problem is with the respiratory system or the cardiovascular system.

You measure arterial P_O2, arterial hemoglobin per cent saturation, and arterial P_CO2.

If the problem is with the respiratory system, what should the numbers be for these parameters? (2 pts)

Arterial P_O2

Hemoglobin percent saturation:

arterial P_CO2:

Explain why. 1 pt.

If the problem is with the cardiovascular system (such as anemia or a weak left ventricle), what should the numbers be for these parameters? Explain why (2 pts)

Arterial P_O2:

arterial hemoglobin percent saturation:

arterial P_CO2:

Explain why.

Suppose you determine that the problem is with the respiratory system.

Your next goal is to determine whether the problem is with alveolar ventilation (getting fresh air to the alveoli, as can occur with asthma) or diffusion (getting oxygen from alveoli to blood, as can occur with pulmonary edema). Assume you can measure oxygen (P_O2) in the exhaled air, the alveoli, and the arterial blood.

How should these P_O2 values compare to normal if the problem is inadequate alveolar ventilation? (3 pts)

exhaled P_O2?

alveolar P_O2?

arterial P_O2?

Explain why .

How should these P_O2 values compare to normal if the problem is a poor alveolar diffusing capacity? (2 pts)

exhaled P_O2?

alveolar P_O2?

arterial P_O2?

Explain why.

Answer 1

1.

The hemoglobin levels are normal ,so we can eliminate anemia as diagnosis.A disorder which causes generalised weakness,due to less amount of hb and less amount of oxygen to various parts of the body.Thus leading to ischaemia.

2.Arterial blood gas test is carried out if the problem is within respiratory tract.

Then Arterial PO2 would be less than 75 mmHg.Normal range is 75- 100mmHg

Arterial PCO2 would be more than 40 mmHg.Normal range is 35-45mmHg.

Hemoglobin percent saturation is the amount of oxygen carried by hemoglobin.It may be normal that is 97-98% if it has normal hemoglobin.

3.If problem is in cardiovascular system like ventricular hypertrophy or anemia.

Arterial PO2 will be normal around 75-100,if the oxygen supply to the lungs is normal.

Arterial PCO2 will be around 35-45 normal,as CO2 will be eliminated by lungs properly.

Arterial hb percent saturation will be decreased less than 96% as low hb will carry less amount of oxygen and causes ischaemia.