Cardiopulmonary Exercise Testing
MITCHELL HOROWITZ
Outline
 Description of CPET
 Who should and who should not get CPET
 When to terminate CPET
 Exercise physiology
 Define terms: respiratory exchange ratio, ventilatory
equivalent, heart rate reserve, breathing reserve, oxygen
pulse
 Pattern of CPET results COPD vs CHF
Rationale for Exercise Testing
 Cardiopulmonary measurements
obtained at rest may not estimate
functional capacity reliably
Clinical Exercise Tests
 6-min walk test
 Submaximal
 Shuttle walk test
 Incremental, maximal, symptom-limited
 Exercise bronchoprovocation
 Exertional oximetry
 Cardiac stress test
 CPET
Karlman Wasserman
Coupling of External Ventilation
and Cellular Metabolism
Adaptations of Wasserman’s Gears
General Mechanisms of Exercise Limitation
 Pulmonary
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Ventilatory
Respiratory muscle
dysfunction
Impaired gas exchange
 Peripheral
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 Cardiovascular
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Reduced stroke volume
Abnormal HR response
Circulatory abnormality
Blood abnormality
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Inactivity
Atrophy
Neuromuscular dysfunction
Reduced oxidative capacity
of skeletal muscle
Malnutrition
 Perceptual
 Motivational
 Environmental
What is CPET?
 Symptom-limited exercise
test
 Measure airflow, SpO2, and
expired oxygen and carbon
dioxide
 Allows calculation of peak
oxygen consumption,
anaerobic threshold
Components of Integrated CPET
 Symptom-limited
 ECG
 HR
 Measure expired gas
 Oxygen consumption
 CO2 production
 Minute ventilation
 SpO2 or PO2
 Perceptual responses
 Breathlessness
 Leg discomfort
Modified Borg CR-10 Scale
Indications for CPET
 Evaluation of dyspnea
 Distinguish cardiac vs pulmonary vs peripheral limitation vs other
 Detection of exercise-induced bronchoconstriction
 Detection of exertional desaturation
 Pulmonary rehabilitation
 Exercise intensity/prescription
 Response to participation
 Pre-op evaluation and risk stratification
 Prognostication of life expectancy
 Disability determination
 Fitness evaluation
 Diagnosis
 Assess response to therapy
Mortality in CF Patients
 Nixon et al; NEJM 327: 1785; 1992.
 Followed 109 patients with CF for 8 yrs from CPET
 Peak VO2 >81% predicted:
83% survival
 Peak VO2 59-81% predicted: 51% survival
 Peak VO2 <59% predicted:
28% survival
Mortality in CHF Patients
 Mancini et al; Circulation 83: 778; 1991.
 Peak VO2 >14 ml/kg/min:
 1-yr survival 94%
 2-yr survival 84%
 Peak VO2 ≤14 ml/kg/min:
 1-yr survival 47%
 2-yr survival 32%
CPET to Predict Risk of Lung Resection in Lung Cancer
Lim et al; Thorax 65:iii1, 2010
Alberts et al; Chest 132:1s, 2007
Balady et al; Circulation 122:191, 2010
 Peak VO2 >15 ml/kg/min

No significant increased risk of complications or death
 Peak VO2 <15 ml/kg/min

Increased risk of complications and death
 Peak VO2 <10 ml/kg/min
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
40-50% mortality
Consider non-surgical management
Absolute Contraindications to CPET
Acute MI
Unstable angina
Unstable arrhythmia
Acute endocarditis, myocarditis, pericarditis
Syncope
Severe, symptomatic AS
Uncontrolled CHF
Acute PE, DVT
Respiratory failure
Uncontrolled asthma
SpO2 <88% on RA
Acute significant non-cardiopulmonary disorder that may affect or be
adversely affected by exercise
 Significant psychiatric/cognitive impairment limiting cooperation
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Relative Contraindications to CPET
 Left main or 3-V CAD
 Severe arterial HTN (>200/120)
 Significant pulmonary HTN
 Tachyarrhythmia, bradyarrhythmia
 High degree AV block
 Hypertrophic cardiomyopathy
 Electrolyte abnormality
 Moderate stenotic valvular heart disease
 Advanced or complicated pregnancy
 Orthopedic impairment
Indications for Early Exercise Termination
 Patient request
 Ischemic ECG changes
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2 mm ST depression
Chest pain suggestive of ischemia
Significant ectopy
2nd or 3rd degree heart block
Bpsys >240-250, Bpdias >110-120
Fall in BPsys >20 mmHg
SpO2 <81-85%
Dizziness, faintness
Onset confusion
Onset pallor
CPET Measurements
 Work
 R
 VO2
 SpO2
 VCO2
 ABG
 AT
 Lactate
 HR
 CP
 ECG
 Dyspnea
 BP
 Leg fatigue
Exercise Modality
 Advantages of cycle ergometer
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Cheaper
Safer
 Less danger of fall/injury
 Can stop anytime
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Direct power calculation
 Independent of weight
 Holding bars has no effect
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Little training needed
Easier BP recording, blood draw
Requires less space
Less noise
 Advantages of treadmill
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Attain higher VO2
More functional
Incremental vs Ramp Exercise Test Protocol
INCREMENTAL
RAMP
WORK
WORK
TIME
TIME
Physiology and Chemistry
 Slow vs fast twitch fibers
 Buffering of lactic acid by bicarbonate
 CO2 production from carbonic acid
 Respiratory exchange ratio
 Ventilatory equivalent of oxygen
 Ventilatory equivalent of carbon dioxide
 Graphical determination of AT
 Fick Equation
 Oxygen pulse
Properties of Skeletal Muscle Fibers
 Red = Slow twitch = Type I
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Sustained activity
High mitochondrial density
Metabolize glucose
aerobically
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 White = Fast twitch = Type II
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1 glucose yields 36 ATP
Rapid burst exercise
Few mitochondria
Metabolize glucose
anaerobically

Rapid recovery

1 glucose yields
2 ATP and 2 lactic acid
Slow recovery
Lactic Acid is Buffered by Bicarbonate
Lactic acid + HCO3 → H2CO3 + Lactate
↓
H2O + CO2
Respiratory Exchange Ratio
RER= CO2 produced / O2 consumed
= VCO2 / VO2
Ventilatory Equivalents
 Ventilatory equivalent for carbon dioxide =
Minute ventilation / VCO2
 Efficiency of ventilation
 Liters of ventilation to eliminate 1 L of CO2
 Ventilatory equivalent for oxygen =
Minute ventilation / VO2
 Liters of ventilation per L of oxygen uptake
Relationship of AT to RER and Ventilatory Equiv for O2
 Below the anaerobic threshold, with carbohydrate
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metabolism, RER=1 (CO2 production = O2 consumption).
Above the anaerobic threshold, lactic acid is generated.
Lactic acid is buffered by bicarbonate to produce lactate,
water, and carbon dioxide.
Above the anaerobic threshold, RER >1 (CO2 production > O2
consumption).
Carbon dioxide regulates ventilation.
Ventilation will disproportionately increase at lactate
threshold to eliminate excess CO2.
Increase in ventilatory equivalent for oxygen demarcates the
anaerobic threshold.
Lactate Threshold
Determination of AT from RER Plot (V Slope Method)
Determination of AT from Ventilatory Equivalent Plot
Wasserman 9-Panel Plot
Oxygen Consumption: Fick Equation
Fick Equation:
Arterial oxygen content =
(1.34)(SaO2)(Hgb)
Q = VO2 / C(a-v)O2 Venous oxygen content =
(1.34)(SvO )(Hgb)
VO2 = Q x C(a-v)O2
VO2 = SV x HR x C(a-v)O2
2
Heart disease
Heart disease
Lung disease
Muscle disease
Deconditioning
Anemia
Lung disease (low SaO2)
Oxygen Pulse
 Oxygen Pulse:
“. . .the amount of oxygen
consumed by the body from
the blood of one systolic
discharge of the heart.”
Henderson and Prince
Am J Physiol 35:106, 1914
Oxygen Pulse = VO2 / HR
Fick Equation:
VO2 = SV x HR x C(a-v)O2
VO2/HR = SV x C(a-v)O2
Oxygen Pulse ~ SV
Interpretation of CPET
 Peak oxygen consumption
 Peak HR
 Peak work
 Peak ventilation
 Anaerobic threshold
 Heart rate reserve
 Breathing reserve
Heart Rate Reserve
 Comparison of actual peak HR and predicted peak HR
= (1 – Actual/Predicted) x 100%
 Normal <15%
Estimation of Predicted Peak HR
 220 – age
 For age 40: 220 - 40 = 180
 For age 70: 220 - 70 = 150
 210 – (age x 0.65)
 For age 40: 210 - (40 x 0.65) = 184
 For age 70: 210 - (70 x 0.65) = 164
Breathing Reserve
 Comparison of actual peak ventilation and predicted peak
ventilation
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Predicted peak ventilation = MVV, or FEV1 x 35
= (1 – Actual/Predicted) x 100%
 Normal >30%
Comparison CPET results
Predicted Peak HR
Peak HR
MVV
Peak VO2
AT
Peak VE
Breathing Reserve
HR Reserve
Borg Breathlessness
Borg Leg Discomfort
Normal
150
150
100
2.0
1.0
60
40%
0%
5
8
CHF
150
140
100
1.2
0.6
40
60%
7%
4
8
COPD
150
120
50
1.2
1.0
49
2%
20%
8
5
Cardiac vs Pulmonary Limitation
 Heart Disease
 Breathing reserve >30%
 Heart rate reserve <15%
 Pulmonary Disease
 Breathing reserve <30%
 Heart rate reserve >15%
CPET Interpretation
Peak VO2 HRR
Normal
>80%
Heart disease <80%
Pulm vasc dis <80%
Pulm mech dis <80%
Deconditioning <80%
<15%
<15%
<15%
>15%
>15%
BR AT/VO2max A-a
>30%
>30%
>30%
<30%
>30%
>40%
<40%
<40%
>40%
>40%
normal
normal
increased
increased
normal
SUMMARY
 Cardiopulmonary measurements obtained at rest may
not estimate functional capacity reliably.
 CPET includes the measurement of expired oxygen and
carbon dioxide.
 The Borg scale is a validated instrument for
measurement of perceptual responses.
 CPET may assist in pre-op evaluation and risk
stratification, prognostication of life expectancy, and
disability determination.
SUMMARY
 Cycle ergometer permits direct power calculation.
 Peak VO2 is higher on treadmill than cycle ergometer.
 Peak VO2 may be lower than VO2max.
 Absolute contraindications to CPET include unstable
cardiac disease and SpO2 <88% on RA.
 Fall in BPsys >20 mmHg is an indication to terminate CPET.
 1 glucose yields 36 ATP in slow twitch fiber, and 2 ATP + 2
lactic acid in fast twitch fiber.
 RER= CO2 produced / O2 consumed
SUMMARY
 Above the anaerobic threshold, CO2 production exceeds
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O2 consumption.
Ventilation will disproportionately increase at lactate
threshold to eliminate excess CO2.
AT may be determined graphically from V slope method or
from ventilatory equivalent for CO2.
Derived from the Fick equation, Oxygen Pulse = VO2 / HR,
and is proportional to stroke volume.
In pure heart disease, BR is >30% and HRR <15%.
In pure pulmonary disease, BR is <30% and HRR >15%.