Exercise Physiology and Pathophysiology

Question 1

1. Describe the normal cardiac response to exercise.

Answer 1

stroke volume increases at low levels of work but levels off afterward, the increase in CO is mainly due to increased frequency, well trained athletes have more reserve stroke volume and are able to respond with increases in stroke volume more than untrained athletes

Question 2

1. Describe the normal respiratory responses to exercise. Comment on ventilatory reserve in this situation.

Answer 2

during early exercise, tidal volume increases until 50-60% of vital capacity is reached, beyond this point minute ventilation increases

ventilatory in normal subjects is adequate so that flow limitation is not reached during exercise

Question 3

1. Describe the factors contributing to the anaerobic threshold in a healthy person.

Answer 3

subjects that exercise at high levels, oxygen delivery becomes insufficient for the metabolic needs of the exercising muscles

“weakest link” in healthy subjects is cardiac output, there is no ventilatory limitation to exercise nor gas exchange in normal subjects

Question 4

2. Understand how and why the dead space fraction changes with exercise in health and disease.

Answer 4

tidal volume increases initially which causes a reduction in dead space ventilation

Question 5

3. Describe the clinical indications for exercise testing.

Answer 5

measure exercise tolerance
evaluation for respiratory disability
ascertain the presence of exercise hypoxemia

Question 6

4. Understand the components of max. oxygen consumption, breathing reserve, anaerobic threshold and their utility in exercise testing.

Answer 6

work rate (watts of exercise output)
heart rate
blood pressure
collection of expired gases to calculate Vo2 and Vco2

useful in determining if exercise limitation is due to cardiac or pulmonary causes

Question 7

5. Describe the mechanism of exercise limitation in cardiac disease.

Answer 7

oxygen delivery to exercising muscles is reduced, resulting in early anaerobic metabolism, lactate accumulation and dyspnea

max. heart rate response is reached at a low Vo2

in heart failure increased venous return during exercise can lead to pulmonary congestion (dyspnea and hypoxiema) or cardiac arrhythmias may develop

Question 8

5. Describe the mechanism of exercise limitation in COPD.

Answer 8

physiologic hallmark is reduced expiratory flow and overinflation, both increasing work to breath, and increased EELV (end-expiratory lung volume)

increased ventilation may not be sufficient to keep CO2 normal and PaCO is increased (gas exchange limitation)

Question 9

5. Describe the mechanism of exercise limitation in interstitial lung disease.

Answer 9

limited ability to increase VT dictates increase frequency
hypoxemia is caused by areas of low V/Q, and involvement of the pulmonary vascular bed

inability to increase tidal volume; destruction of pulmonary vascular involvement causes increased V/Q

Question 10

5. Describe the mechanism of exercise limitation in pulmonary vascular disease.

Answer 10

pulmonary vascular disease causes hypoxemia secondary to V/Q mismatching, low mixed venous O2 and R/L shunt if the patient has a patent foramen ovale, increase in resistance means CO cannot increase appropriately

Question 11

What does VO2 sand for?

Answer 11

oxygen consumption

Question 12

CO shows a ____ relationship with oxygen consumption.

Answer 12

linear

Question 13

The difference between the maximal voluntary ventilation and the minute ventilation achieved at maximal exercise is called _____ _____.

Answer 13

breathing reserve