Cardiopulmonary Stress
Testing
Danielle Rowe BS RRT, RPFT
Senior Clinical Sales Specialist
Carefusion
WHAT IS THE PURPOSE OF CPX
TESTING?
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It is an assessment of a subject’s functional
(work) capacity under stress.
We judge this functional capacity by primarily
evaluating peak VO2.
After functional capacity is established, we
then are provided with insight on cause of
limitations if they exist.
Possible limitations to Exercise
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Ventilation
Gas Exchange
Circulation (inc. ECG)
Metabolism
metabolism
O2
CO2
Peripheral
Gas Exchange
Pulmonary
Gas Exchange
Indications For Cardiopulmonary
Exercise Testing
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Evaluation of exercise tolerance
Evaluation of undiagnosed exercise
intolerance
Evaluation of patients with cardiac disease
Evaluation of patients with Respiratory
disease
Specific Clinical Applications

Preop assessment on certain populations, rehab
evaluations, disability, transplantation etc.
From ATS/ACCP
Max or Submax Testing
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For Cardiopulmonary diagnostic purposes,
MAXIMAL testing is performed.
We aim to stress the cardio-respiratory
system until we identify the factor which
limits exercise capacity.
Sub max test are more common in athletics
training, rehabilitation etc.
Exercise Protocols
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Cycle Ergometry
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Ramp, typically increases of 5 -30 W/minute
Aim to have exercise portion of testing lasting
approx. 10 minutes
1-3 minutes resting data
1-3 minutes unloaded pedaling
Treadmill
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Speed constant and grade increased (Balke
Protocol). 2 mph, 0% grade and then the grade is
increased 2-3% every minute.
Speed and grade are both increased ( Bruce
Protocol). 1.7 mph, 10% grade and then increased
by .8 mph and 2% grade every 3 minutes.
Bike vs Treadmill
Bike
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VO2 Max
Work Rate Meas.
Blood gas collection
Noise and artifacts
Safety
Wt. bearing in obese
Leg muscle fatigue
lower
Yes
easier
less
safer
less
often
Treadmill
higher
No
harder
more
less safe?
more
less
Bike vs. Treadmill cont.
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Bike
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All things considered, bike is considered the most
appropriate for patients.
This is due to ability to accurately quantify work and the
minimizing of test artifacts.
Just remember vigorous encouragement is often needed
near peak of exercise test to help overcome and push
through leg muscle fatigue.
Treadmill
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VO2 max is often 5-10% higher
Most appropriate for athletes and patients in whom
abnormalities may occur only with the highest demand
( cardiac ischemia).
Selecting the Work Rate
5 Watts/min
Severe impairment (e.g. patient who is
confined to home or walks only short distances)
10 Watts/min
Moderate impairment (e.g. patient who
walks one or two city blocks before symptoms)
15 Watts/min
Mild impairment or sedentary older
patient
20 Watts/min
Sedentary younger patient
25 Watts/min
Active younger patient (regular sports,
physical exercise)
30 Watts/min
Athletic and fit (competitive sports)
40 Watts/min
Extremely fit (highly competitive)
Chris Cooper, MD.. Harbor UCLA Medical
Was it a Good Test ?
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How can we tell ?
Most common problem seen is sub-maximal
performance.
Patients are supposed to “suffer” - that is the
whole idea of the test - to put them under stress.
Don’t stop when the patient hits Max Predicted
Heart Rate - carry on until the patient stops.
Often the best Indicator..
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RER
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“Although no one RER value defines
maximal effort, values greater than
1.15 are more likely to be associated
with near maximal or maximal
effort.”
From ATS/ACCP Statement
RER (or RQ) = VCO2/VO2
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At Baseline, RER < 0.8
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If it isn’t, check for hyperventilation
If no hyperventilation, something is wrong
Many patients hyperventilate in the baseline
state
At end of test, RER > 1.15
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Indicates maximal exercise effort and therefore
a good test
Indications for Exercise
Termination
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Chest pain suggestive of ischemia
Ischemic ECG changes
Complex ectopy
Second or third degree heart block
Fall in systolic pressure >20 mmHg from the highest
value during the test.
Hypertension ( >250 mmHg sys; >120 mmHg diastolic)
Severe desaturation: SpO2 ≤ 80% when accompanied by
symptoms and signs of severe hypoxemia
Sudden pallor
Loss of confusion
Dizziness or faintness
Signs of respiratory failure
From ATS/ACCP Statement
VO2 Peak/Max
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Maximal Oxygen Uptake (VO2 max)
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Peak Oxygen Uptake ( VO2 peak)
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Represents the highest VO2 that can be reached as
evidenced by a failure for VO2 to increase further
despite and increase in work rate.
Represents the highest VO2 reached during the test
where a presumed maximal effort was given.
These Terms are often used interchangeably.
Oxygen Consumption

The amount of oxygen used per minute.
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250 mL/min at rest (3.5 mL/min/kg)
5,000 mL/min at strenuous exercise (>70
mL/min/kg)
Low
Average
AGE
Men
Women
Men
Women
20-29 yrs
<25
<24
34 - 42
31 - 37
30-39 yrs
<23
<20
31 – 38
28 - 33
40-49 yrs
<20
<17
27 – 35
24 -30
50-59 yrs
<18
<15
25 – 33
21 - 27
60-69 yrs
<16
<13
23 – 30
18 - 23
Expected Vo2 mL/min/kg values from American Heart Association
Weber- Janicki Classification
in heart failure
Severity
Class
Peak Vo2 mL/kg/min
None to Mild
A
>20
Mild to Moderate
B
16 – 20
Moderate to Severe
C
10 – 16
Severe
D
6 -10
Very Severe
E
<6
Peak VO2 Cont.
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Peak VO2 is often used in the course of treating
heart failure and in selecting heart transplant
candidates:
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Typically these subjects that test with a peak VO2
<14 ml/min/kg are strongly considered for
transplantation.
Peak Vo2 is often considered with major surgery
especially abdominal surgery in elderly or sick
patients.
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>20 ml/min/kg good prognosis
<15 ml/min/kg high risk
VO2- Work relationship
• VO2/Work slope = Normal is right around 10/ml/min/watt with relatively
small range of normal reported in many studies. Typically (8.5- 11) considered
normal.
• Shallower slope, so a value < 8.5- 8.7 ml/min/watt point to a problem of O2
flow or O2 utilization.
Anaerobic Threshold (AT)
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Lactacte Threshold, Lactic Acid Threshold,
Gas Exchange threshold, Ventilatory
threshold etc..
The highest level of oxygen consumption
that can be sustained without developing
metabolic acidosis.
The point at which anaerobic
metabolism starts to contribute.
AT cont.
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Normally occurs at about 50-60% of
Vo2 max predicted however there is a
wide range of normal reported (3580%).
40% is the generally accepted lower
limit of normal used clinically.
Detecting AT
Invasive determination
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Arterial Lactate measurements. AT is
graphically determined by plotting lactate
concentration vs. Vo2.
AT by V-Slope Method
AT by Dual Criteria Method
AT summary
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Athletes can do more activity aerobically so AT
is increased.
In diseases ( most cardiovascular) that affect
O2 supply to exercising muscles , the AT is
often found to be early. This can also occur in
more rare conditions with mitochondrial
myopathies.
In clinical CPX testing you are searching for an
early AT. If it is not early, then it really does
not matter precisely where it occurred.
Cardiac Parameters
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Heart Rate and HR reserve
BP <220/90
O2 pulse
ECG
HR –VO2 relationship
Heart Rate and HR reserve
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Many formulas exist for predicting max HR.
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220- age
210- (age × 0.65)
HR reserve is the difference between the
predicted max and the achieved max.
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Normally there is very little to no reserve in
normal subjects giving maximal effort.
Often a HRR < 15 beats/min is normal.
HR- VO2 Relationship
200 -
Predicted Maximum Heart Rate
HRR = 0
HR
(b/min)
0
0
|
VO2
Max
Predicted
HR/VO2 normal = 3-4 beats/ml/min/kg
O2 pulse
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VO2/HR
Amount of O2 uptake per each beat of heart.
Dependent on stroke volume and O2 uptake.
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O2 pulse = SV × C(a-v)O2
O2 pulse normally increases with incremental
exercise due to increases in both SV and O2
extraction.
When O2 content and C(a-v)O2 are maximal
and assumed to be normal ( approx. 15 ml/dl),
stroke volume can be estimated:
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SV= O2 pulse/15 *100
Ventilatory Parameters
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VE
RR
Tidal volume
Breathing reserve
Inspiratory capacity trending ( Ex. FVL)
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Capacity, reserve assessment
VE and Breathing reserve
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Measure Spirometry and MVV prior to exercise test. Then
decide which to use as predictor of maximal ventilation. Quality
of these baseline measurements is key….be careful!
Often MVV may not be the best indicator of capacity as breathing
pattern of the 12-15 sec effort is not typically a pattern subject
adopts during exercise.
FEV1 × 35 or 40 is often used to estimate MVV or capacity.
Things to consider:
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Effort and quality of baseline spirometry and MVV. Can I use either?
It may be better to use actual MVV in cases of upper airway
obstruction or neuromuscular weakness.
Breathing reserve= (MVV-VE max/ MVV)× 100
Normal = 20-30 %. Typically < 15% considered
low.
Breathing pattern
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The rise in VE during exercise is associated
with an increase in both depth and
frequency of breathing.
Tidal Volume- Vt typically increases until it
reaches about 50-60% of VC or 70% of IC.
Further increases in VE are accomplished by
respiratory rate.
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Typically the rate does not normally exceed around
55 bpm.
Exercise Tidal FVL tracings
Normal
What happens here?
Ventilatory Equivalents
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How many liters of air we need to breath to
exchange 1 L of gas.
VEVO2
VECO2
Indicators of efficiency of ventilation.
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Increases in ventilatory equivalents:
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Often found in diseases in which pulmonary blood flow
is abnormally reduced to ventilated gas exchange units.
Ventilatory Equivalents
(Efficiency of ventilation)
VE/CO2
40
VE/VO2
20
AT
RC
0
VE/VO2 @ AT: 26.5 (22.1 – 30.9)
NORMAL VALUES:
Ref: Wasserman
VE/VCO2 @ AT: 29.1 (24.8 – 33.4)
Arterial Blood Sampling
Do we need it?
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Sometimes….
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When the adequacy of pulmonary gas exchange is
in question up front. Typically in diseases like ILD,
pulmonary vascular disease, COPD with low DLCO
etc.
When concern over increased dead space is and
issue. You want real VD/VT measurements.
When patients have an abnormal initial CPET
maybe showing increased VE/VCO2 but no specific
reason. Was it hyperventilation or due to increased
VD.
If you do it, do it right! Use and Arterial line. No
single samples at peak exercise.
Additional pieces of information
when blood gas sampling is done
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Information about ability to exchange
oxygen.
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PaO2- normally >80 mmHg and should not
decrease with exercise.
P (A-a)O2- should be <35 mmHg at peak.
SaO2
ABG cont..
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VD/VT = (PaCO2 – PECO2)/PaCO2
Fraction of each breath “wasted” on ventilating
anatomic and physiologic dead space.
You need PaCO2 to get a true VD/VT. You
cannot accurately estimate!
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The estimated VD/VT that is often reported uses
end-tidal PCO2 in place of PaCO2 which can be
misleading.
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Normally PetCo2 is a little less than PaCO2 at rest but
becomes greater than PaCO2 with exercise leading to an
overestimation of VD/VT.
With lung disease PetCO2 may remain below PaCO2 even
with exercise causing an underestimation of dead space.
VD/VT
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Normal at rest is 30-40%.
Should fall with exercise due to increasing
tidal volume.
Typically at peak exercise we should see
values less than 28% in subjects < 40 yrs.
Values less than 30% normal in subjects
>40 yrs.
Putting it all together
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Was it a good test?
Can subject achieve normal VO2 and do normal
amount of “work”?
Is there a premature metabolic acidosis?
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Low AT
Is there a cardiovascular limitation?
Is there a ventilatory (mechanics) limitation?
Does pulmonary gas exchange contribute to
exercise limitation?
Obesity
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High O2 cost to perform work.
Peak VO2/kg is low when expressed per kg
of actual wt but normal when expressed per
kg of ideal wt.
Low PaO2 that often normalizes with
exercise.
Failure to develop normal ventilatory
compensation for metabolic acidosis.
Cardiovascular disease
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Low VO2
Early AT
Reduced maximal O2 pulse
Steep HR/VO2 relationship
Peak HR variable- may be normal or
reduced.
Often increased ventilatory reserve
Ventilatory limitation
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Low VO2
High VD/VT
Low breathing reserve
High heart rate reserve
AT normal or not reached
Failure to develop respiratory
compensation for metabolic acidosis.
Thank you