Daniel Walden

The Ventilatory Response to Exercise

Lab: Thursday, 12:40-3:25

October 21, 2009

1. Construct 3 plots of ventilation, frequency, and tidal volume vs work rate for the progressive test.

Relationship Between Ventilation and Increasing Work Rate

05

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0 1 2 3 4 5 6 7 8 9 10

Work Rate (kgm/min)

VE BTPS (L/min)

Relationship Between Frequency (Breaths/min) and Increasing Work Rate

0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12

Work Rate (kgm/min)

Frequency (Breaths/min)

Relationship Between Tidal Volume and Increasing Work Rate

0

0.5

1

1.5

2

2.5

3

0 2 4 6 8 10 12

Work Rate (kgm/min)

Tidal Volume (L/breath)

2. Calculate the ventilatory equivalent and graph this. Locate the “ventilatory threshold on your graph of VE/V02 and see if it agrees with your estimate from question 1.

Relationship between Ventilatory Equivalents and Increasing Work Rate

0

5

10

15

20

25

30

35

40

45

0 2 4 6 8 10 12

Work Rate (kgm/min)

VE/V02 (02

moving/02 consumed)

VE/V02

3. The ventilatory threshold marks the onset of hyperventilation. What is the physiological advantage of hyperventilating at this point in the exercise test?

The physiological advantage of hyperventilating during strenuous had to do with the lactic acid produced that creates an imbalance between acid-base. When hyperventilating, the respiratory system a role in buffering the hydrogen ions produced through a reaction involving both the hydrogen ions and the plasma bicarbonate resulting

in H20 and CO2 products, thus dissipating the hydrogen ion concentration via a C02 product.

4. Did the percent saturation of hemoglobin in the arterial blood remain high throughout the GXT? What does this indicate relative to the ability of the lungs to perform their job?

The saturation of hemoglobin remains high throughout the GXT, thus the lungs are performing their job. If the saturation levels were lower than resting level then we would know that the limiting factor of blood saturation and supplying the muscles with sufficient oxygenated blood. However, that is not that case, since the number is relatively consistent, we know the lungs are performing their job, it is actually the cardiac output that is the limiting factor because the heart cannot pump enough of the oxygenated blood fast enough.

5. Consult the oxygen-hemoglobin dissociation curve in your textbook. a) Assuming that the oxygen content of the arterial blood is 200 ml/L when the hemoglobin is 100% saturated, use the values for % Sa02 that you measured in maximal exercise to estimate the ACTUAL oxygen content of the blood during the final stage.

b) Mixed venous oxygen content is measured as blood enters the right heart from all areas of the body. If the mixed venous P02 were 15 mmHg, what would the oxygen saturation be during the final stage? What would the oxygen content of the mixed venous blood be?

c) Estimate the maximal cardiac output for your subject, using the formula below.

CO max = V02 max / (a – v 02 difference)

6. Elite endurance athletes often show arterial desaturation during maximal exercise yet most healthy, untrained person do not. How does one explain this curing finding?