Exercise Testing

Question 1

what is VO2 max

Answer 1

VO2 is the volume of oxygen being used by the cells. VO2 max is where there is a plateau in oxygen consumption during a graded exercise test beyond which no increase in effort can raise it.

Question 2

What is a CPET?

Answer 2

A cardiopulmonary exercise test. It acquires continuous measurements of metabolic, cardiovascular and Respiratory parameters over an 8 -15 minute effort in which exercise progresses incrementally from a minimal movement to a maximal symptom limited effort.

Question 3

What measurements does a CPET produce?

Answer 3

Oxygen uptake, carbon dioxide output, tidal volume, minute ventilation, Respiratory rate, heart rate, end tidal oxygen, end tidal CO2, ECG, BP, O2 sats, power output.

Question 4

What useful ratios does the CPET produce?

Answer 4

R value- VCO2/ VO2
Oxygen pulse- VO2/ heart rate
Ventilatory equivalents for oxygen (VE/VO2)
Ventilatory equivalents for carbon dioxide (VE/VCO2)

Question 5

What is the relationship between oxygen consumption and power output ?

Answer 5

It is linear.

Question 6

What is the primary limitation for exercising muscle during a progressive work test ?

Answer 6

The events of muscle contraction
The maximal production capacity of ATP
The maximal delivery capacity of oxygen or carbon fuel sources to mitochondria - this is limited by percentage of blood flow to exercising muscles whilst preserving cerebral perfusion.

Question 7

How does R reflect fuel utilisation?

Answer 7

A fasting subject at rest will primarily metabolize fat and the R value will be low- around 0.7.
The same subject given a large glucose load will have an R of over 0.9.
During exercise the R value gradually increases as we switch from fat as fuel to carbohydrate. This is because as exercise work load increases the capacity of mitochondria to use free fatty acids is limited and carbohydrate becomes a progressively more important fuel source.

Question 8

Why does the R value exceed 1?

Answer 8

At the onset of metabolic acidosis there is tissue buffering with bicarbonate and a washout of Co2 stores from systemic tissues, in addition to metabolically generated Co2.

Question 9

What is the fick equation to describe oxygen delivery?

Answer 9

VO2= SV x HR x (arterial O2- venous O2)

Question 10

How does heart rate respond with exercise

Answer 10

It increases in a nearly linear fashion

Question 11

How can maximal heart rate be calculated ?

Answer 11

220 - age in years

Question 12

How does stroke volume change with the onset of exercise ?

Answer 12

Stroke volume is dependent on preload. When a subject becomes upright blood pools in the leg veins so SV reduces. When exercise commences the calf muscles and increased sympathetic tone increase venous return to the heart so SV increases.

Question 13

How does blood flow change during exercise ?

Answer 13

At rest the majority of cardiac output is distributed to the heart, brain, splanchnic circulation, kidneys. The mixed venous saturation returning to the pulmonary artery Is about 75%.

With maximal effort, mixed venous concentration drops to 20%, 85% of Increased cardiac output is diverted to exercising muscle.

Question 14

What is the O2 pulse ?

Answer 14

VO2/ HR = stroke volume/ a- Vo2 extraction
It progressively increases during a CPET and reflects progressive increase in a-VO2 extraction
It will be reduced in anaemic subjects

Question 15

What is the effect of temperature on blood flow during exercise?

Answer 15

It alters allocation of blood flow by sending it to the skin. Increase in temperature during exercise means maximal venous extraction of oxygen is reduced as skin consumes little oxygen. Cardiac output will increase to compensate for this diversion of blood flow

Question 16

What is the response of blood pressure to exercise?

Answer 16

Minimal Increase in the early stages, followed by a progressive increase in systolic pressures at onset of metabolic acidosis.

Question 17

What should you do if blood pressure fails to increase with the onset of heavy exercise

Answer 17

Remove the exercise load, keep legs moving to prevent blood pooling.

Question 18

What does a right shift of the oxygen dissociation curve mean ?

Answer 18

At any given cellular PO2 more oxygen is released

Question 19

What can cause a right shift of the oxygen dissociation curve ?

Answer 19

Increases in temperature, acidity, CO2. Elevation of muscle temperature has the greatest effect

Question 20

What does myoglobin do?

Answer 20

It facilitates movement of oxygen from the muscle capillary to muscle mitochondria. It binds more firmly to oxygen than haemoglobin but the mitochondrial utilisation of oxygen remains fully functional even at partial pressures of O2 as low as 2-3 mmHg.

Question 21

How does training decrease diffusion distance of oxygen in muscles ?

Answer 21

They develop more mitochondria and more extensive capillary networks that reduce diffusion distance which increases oxygen utilisation.

Question 22

How is the majority of CO2 transported in the blood?

Answer 22

As bicarbonate

Question 23

In a normal subject what effect does the capacity of the chest wall to move air have on exercise ventilation

Answer 23

None, maximal capacity for chest wall movement exceeds requirements for maximal exercise ventilation

Question 24

What happens to alveolar PO2 and PCO2 during exercise ?

Answer 24

They stay more or less the same to maintain PO2 of arterial blood, except with heavy exercise PO2 goes down and PCO2 goes up

Question 25

What is tidal volume?

Answer 25

The volume of normal breathing

Question 26

What is functional residual capacity

Answer 26

The lung volume at the beginning of a normal breath

Question 27

What is inspiratory capacity ?

Answer 27

The volume inspired from FRC with a maximal inspiratory effort, reaching the total lung capacity

Question 28

What is vital capacity ?

Answer 28

The maximal volume of gas that can be exhaled from TLC

Question 29

What is FEV1?

Answer 29

The volume expired in the first second of the VC effort.

Question 30

What is residual volume?

Answer 30

The volume of gas remaining in the lung after a maximal expiratory effort

Question 31

What is normal FEV1/ FVC ratio?

Answer 31

70-80%

Question 32

What is MVV (maximal voluntary ventilation)?

Answer 32

The subject is coached to take the deeper, fastest breaths for 12 seconds, the total amount of gas exhaled in that period is multiplied by 5, giving an MVV measurements in L/ minute

Question 33

What relationship does MVV have to FEV1 ?

Answer 33

It is about 40 times

Question 34

What is MVV at rest used to compare with?

Answer 34

It represents a resting measurement of the maximal Ventilatory capacity, which is used for later comparison with the ventilation achieved during a maximal exercise effort.

Question 35

What relationship does maximal exercise ventilation have to MVV?

Answer 35

To maintain alveolar PO2 in healthy subjects only 65-75% of the MVV is required, therefore there in heslthy subjects there is no Ventilatory limitation during a progressive work test

Question 36

How do tidal volume and Respiratory rate change during exercise ?

Answer 36

In the early stages, increase in ventilation comes from increases in tidal volume, but once this reaches 60-70% of vital capacity, additional increases come from increases in Respiratory rate. This is because of the elasticity of the lungs inspired volumes greater than 60% add disproportionately to the work of breathing.

Question 37

Why is inspiratory capacity greater during exercise ?

Answer 37

Because each exercise breath begins below the resting FRC

Question 38

What stimulates ventilation during exercise ?

Answer 38

On intiation of exercise, cortical input initiates the ventilation response. This is further augmented by afferent neural signals from exercising muscles and joints. As exercise progresses, neural output from the brainstem and carotid sinus adjust the exercise ventilation volume to maintain a constant arterial PCO2. With the onset of heavy exercise and onset of acidosis, these systems provide additional stimulation to ventilation, causing PCO2 to drop. This is further stimulated in arterial hypoxaemia

Question 39

Why are there differences between individuals with minute ventilation at a given level of work?

Answer 39

There are different ventilation sensitivities, these are represented by VE/VO2 and VE/VCO2

These sensitivities are inherited and are not altered by training or lifestyle.

Question 40

What is the sit to stand test

Answer 40

A cheap and easy way of assessing exercise capacity. The subject is asked to stand up and sit down as many times as possible in 1 minute.

Question 41

What is the prognostic value of grip strength?

Answer 41

Low grip strength us associated with the presence of hypertension, coronary artery disease, heart failure, stroke or COPD. High grip strength us associated with young age, males, high level of education, employment, physical activity

Question 42

Why is CPET used?

Answer 42

Where the cause of exercise limitation is uncertain
With patients with a known exercise limiting diagnosis but the impairment is more severe than appears attributable to that disorder
It is also used in consideration of advanced heart failure treatments eg transplantation or installation of cardiac assist devices

Question 43

What effect does heart failure have on exercise and the CPET

Answer 43

Reduction in maximal oxygen consumption. This is due to reduced cardiac output
Decreased O2 pulse due to reduced stroke volume , the o2 pulse will also fail to increase despite progressive increases in o2 consumption

Question 44

What effect does HFPEF have on exercise and the CPEt?

Answer 44

Left ventricular filling is impaired as heart rate increases, so stroke volume Decreases concurrent with normal increase in o2 extraction. This causes the o2 pulse to flatten or even decrease as exercise progresses.

Question 45

What else can cause an abnormal O2 pulse ?

Answer 45

Valvular heart disease, severe pulmonary hypertension, exercise induced atrial fibrillation.

Question 46

How does heart failure affect ventilation response during exercise ?

Answer 46

It increases, this is due to increased exercising muscle sympathetic nerve activity and carotid sinus sensitization to the elevated levels of angiotensin and catecholamines observed in chronic heart failure

Question 47

What happens to lung volume and diffusing capacity in heart failure ?

Answer 47

Decreased lung volume and diffusing capacity. This is because of increase in alveolar capillary membrane thickness and varying amounts of extravascular lung water.
Heart failure patients may only reach 40 or 50% of their vital capacity during exercise and this may be due to Decreased lung compliance or increase in carotid body sensitivity.