Mitchell HOROWitz

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Cardiopulmonary Exercise Testing

• Mitchell HOROWitz

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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

3
Rationale for Exercise Testing

• Cardiopulmonary measurements obtained at rest may
  not estimate functional capacity reliably

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Clinical Exercise Tests

• 6-min walk test
• Submaximal
• Shuttle walk test
• Incremental, maximal, symptom-limited
• Exercise bronchoprovocation
• Exertional oximetry
• Cardiac stress test
• CPET

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Karlman Wasserman
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Coupling of External Ventilation and Cellular
Metabolism
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Adaptations of Wassermans Gears
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General Mechanisms of Exercise Limitation

• Pulmonary
• Ventilatory
• Respiratory muscle dysfunction
• Impaired gas exchange
• Cardiovascular
• Reduced stroke volume
• Abnormal HR response
• Circulatory abnormality
• Blood abnormality

• Peripheral
• Inactivity
• Atrophy
• Neuromuscular dysfunction
• Reduced oxidative capacity of skeletal muscle
• Malnutrition
• Perceptual
• Motivational
• Environmental

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What is CPET?

• Symptom-limited exercise test
• Measure airflow, SpO2, and expired oxygen and
  carbon dioxide
• Allows calculation of peak oxygen consumption,
  anaerobic threshold

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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

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Modified Borg CR-10 Scale
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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

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Mortality in CF Patients

• Nixon et al NEJM 327 1785 1992.
• Followed 109 patients with CF for 8 yrs from CPET
• Peak VO2 gt81 predicted 83 survival
• Peak VO2 59-81 predicted 51 survival
• Peak VO2 lt59 predicted 28 survival

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Mortality in CHF Patients

• Mancini et al Circulation 83 778 1991.
• Peak VO2 gt14 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

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CPET to Predict Risk of Lung Resection in Lung
Cancer

• Lim et al Thorax 65iii1, 2010
• Alberts et al Chest 1321s, 2007
• Balady et al Circulation 122191, 2010
• Peak VO2 gt15 ml/kg/min
• No significant increased risk of complications or
  death
• Peak VO2 lt15 ml/kg/min
• Increased risk of complications and death
• Peak VO2 lt10 ml/kg/min
• 40-50 mortality
• Consider non-surgical management

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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 lt88 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 (gt200/120)
• Significant pulmonary HTN
• Tachyarrhythmia, bradyarrhythmia
• High degree AV block
• Hypertrophic cardiomyopathy
• Electrolyte abnormality
• Moderate stenotic valvular heart disease
• Advanced or complicated pregnancy
• Orthopedic impairment

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Indications for Early Exercise Termination

• Patient request
• Ischemic ECG changes
• 2 mm ST depression
• Chest pain suggestive of ischemia
• Significant ectopy
• 2nd or 3rd degree heart block
• Bpsys gt240-250, Bpdias gt110-120
• Fall in BPsys gt20 mmHg
• SpO2 lt81-85
• Dizziness, faintness
• Onset confusion
• Onset pallor

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CPET Measurements

• Work
• VO2
• VCO2
• AT
• HR
• ECG
• BP

• R
• SpO2
• ABG
• Lactate
• CP
• Dyspnea
• Leg fatigue

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Exercise Modality

• Advantages of cycle ergometer
• Cheaper
• Safer
• Less danger of fall/injury
• Can stop anytime
• Direct power calculation
• Independent of weight
• Holding bars has no effect
• Little training needed
• Easier BP recording, blood draw
• Requires less space
• Less noise
• Advantages of treadmill
• Attain higher VO2
• More functional

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Incremental vs Ramp Exercise Test Protocol

• INCREMENTAL

• RAMP

WORK
WORK
TIME
TIME
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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

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Properties of Skeletal Muscle Fibers

• Red Slow twitch Type I
• Sustained activity
• High mitochondrial density
• Metabolize glucose aerobically
• 1 glucose yields 36 ATP
• Rapid recovery

• White Fast twitch Type II
• Rapid burst exercise
• Few mitochondria
• Metabolize glucose anaerobically
• 1 glucose yields
• 2 ATP and 2 lactic acid
• Slow recovery

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Lactic Acid is Buffered by Bicarbonate

• Lactic acid HCO3 ? H2CO3 Lactate
• ?
• H2O CO2

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Respiratory Exchange Ratio

• RER CO2 produced / O2 consumed
• VCO2 / VO2

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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

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Relationship of AT to RER and Ventilatory Equiv
for O2

• Below the anaerobic threshold, with carbohydrate
  metabolism, RER1 (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 gt1 (CO2
  production gt 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.

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Lactate Threshold
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Determination of AT from RER Plot (V Slope Method)

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Determination of AT from Ventilatory Equivalent
Plot
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Wasserman 9-Panel Plot
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Oxygen Consumption Fick Equation

• Fick Equation
• Q VO2 / C(a-v)O2
• VO2 Q x C(a-v)O2
• VO2 SV x HR x C(a-v)O2

Arterial oxygen content (1.34)(SaO2)(Hgb) V
enous oxygen content (1.34)(SvO2)(Hgb)
Heart disease Lung disease Muscle
disease Deconditioning
Anemia Lung disease (low SaO2)
Heart disease
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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 35106, 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

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Interpretation of CPET

• Peak oxygen consumption
• Peak HR
• Peak work
• Peak ventilation
• Anaerobic threshold
• Heart rate reserve
• Breathing reserve

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Heart Rate Reserve

• Comparison of actual peak HR and predicted peak
  HR
• (1 Actual/Predicted) x 100
• Normal lt15

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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

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Breathing Reserve

• Comparison of actual peak ventilation and
  predicted peak ventilation
• Predicted peak ventilation MVV, or FEV1 x 35
• (1 Actual/Predicted) x 100
• Normal gt30

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Comparison CPET results

• Normal CHF COPD
• Predicted Peak HR 150 150 150
• Peak HR 150 140 120
• MVV 100 100 50
• Peak VO2 2.0 1.2 1.2
• AT 1.0 0.6 1.0
• Peak VE 60 40 49
• Breathing Reserve 40 60 2
• HR Reserve 0 7 20
• Borg Breathlessness 5 4 8
• Borg Leg Discomfort 8 8 5

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Cardiac vs Pulmonary Limitation

• Heart Disease
• Breathing reserve gt30
• Heart rate reserve lt15
• Pulmonary Disease
• Breathing reserve lt30
• Heart rate reserve gt15

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CPET Interpretation

• Peak VO2 HRR BR AT/VO2max
  A-a
• Normal gt80 lt15 gt30 gt40 normal
• Heart disease lt80 lt15 gt30 lt40
  normal
• Pulm vasc dis lt80 lt15 gt30 lt40
  increased
• Pulm mech dis lt80 gt15 lt30 gt40
  increased
• Deconditioning lt80 gt15 gt30 gt40
  normal

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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.

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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 lt88 on RA.
• Fall in BPsys gt20 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

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SUMMARY

• Above the anaerobic threshold, CO2 production
  exceeds 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 gt30 and HRR lt15.
• In pure pulmonary disease, BR is lt30 and HRR
  gt15.