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Mitchell HOROWitz

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Title: Mitchell HOROWitz


1
Cardiopulmonary Exercise Testing
  • Mitchell HOROWitz

2
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

4
Clinical Exercise Tests
  • 6-min walk test
  • Submaximal
  • Shuttle walk test
  • Incremental, maximal, symptom-limited
  • Exercise bronchoprovocation
  • Exertional oximetry
  • Cardiac stress test
  • CPET

5
Karlman Wasserman
6
Coupling of External Ventilation and Cellular
Metabolism
7
Adaptations of Wassermans Gears
8
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

9
What is CPET?
  • Symptom-limited exercise test
  • Measure airflow, SpO2, and expired oxygen and
    carbon dioxide
  • Allows calculation of peak oxygen consumption,
    anaerobic threshold

10
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

11
Modified Borg CR-10 Scale
12
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

13
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

14
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

15
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

16
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

17
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

18
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

19
CPET Measurements
  • Work
  • VO2
  • VCO2
  • AT
  • HR
  • ECG
  • BP
  • R
  • SpO2
  • ABG
  • Lactate
  • CP
  • Dyspnea
  • Leg fatigue

20
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

21
Incremental vs Ramp Exercise Test Protocol
  • INCREMENTAL
  • RAMP

WORK
WORK
TIME
TIME
22
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

23
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

24
Lactic Acid is Buffered by Bicarbonate
  • Lactic acid HCO3 ? H2CO3 Lactate
  • ?
  • H2O CO2

25
Respiratory Exchange Ratio
  • RER CO2 produced / O2 consumed
  • VCO2 / VO2

26
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

27
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.

28
Lactate Threshold
29
Determination of AT from RER Plot (V Slope Method)

30
Determination of AT from Ventilatory Equivalent
Plot
31
Wasserman 9-Panel Plot
32
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
33
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

34
Interpretation of CPET
  • Peak oxygen consumption
  • Peak HR
  • Peak work
  • Peak ventilation
  • Anaerobic threshold
  • Heart rate reserve
  • Breathing reserve

35
Heart Rate Reserve
  • Comparison of actual peak HR and predicted peak
    HR
  • (1 Actual/Predicted) x 100
  • Normal lt15

36
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

37
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

38
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

39
Cardiac vs Pulmonary Limitation
  • Heart Disease
  • Breathing reserve gt30
  • Heart rate reserve lt15
  • Pulmonary Disease
  • Breathing reserve lt30
  • Heart rate reserve gt15

40
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

41
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.

42
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

43
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.
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