cardiopulmonary exercise testing

Dr. Avinash D. ArkeMD FNB

Introduction Cardiopulmonary exercise testing - assessment of the

integrative exercise responses involvingpulmonary, cardiovascular,haematopoietic, neuropsychological, andskeletal muscle systems

THE GAS TRANSPORT SYSTEM

Coupling of External Ventilation and Cellular Metabolism

General Mechanisms of Exercise LimitationPulmonary

VentilatoryRespiratory muscle

dysfunctionImpaired gas exchange

CardiovascularReduced stroke volumeAbnormal HR responseCirculatory abnormalityBlood abnormality

PeripheralInactivityAtrophyNeuromuscular

dysfunctionReduced oxidative

capacity of skeletal muscle

MalnutritionPerceptualMotivationalEnvironmental

Learning objectives 1. Indications for CPET; 2. Methodology—equipment, modality, protocols, conduct of the

test, measurements and graphic interrelationships safety, and personnel issues;

3. Measurements and graphic interrelationships, the physiologic response to exercise, in “normal” subjects, and the consequences of pathophysiologic derangements on exercise performance;

4. Normal reference values; 5. Interpretation, including case study analysis; and 6. Future recommendations for research.

The Fick equationFick equation states that oxygen uptake (VO2) equals cardiac

output times the arterial minus mixed venous oxygen content:VO2 = (SV x HR) x (CaO2 - CvO2)

Where, SV is the stroke volume, HR is the heart rate, CaO2 is the arterial oxygen content, and CvO2 is the mixed venous oxygen content.

Oxygen uptake is often normalised for body weight and expressed in units of ml O2/kg/min.

One metabolic equivalent (MET) is the resting oxygen uptake in a sitting position and equals 3.5 ml/kg/min.

At maximal exercise, the Fick equation is expressed as follows:

VO2max = (SVmax x HRmax) x (CaO2max - CvO2max)

Respiratory exchange ratio (RER)VO2 / VCO2Normal – 1With exercise 0.7 / 0.8If > 1.1, abnormal

Ventilatory anaerobic thresholdVO2 at which lactate starts rising

Indications

Contraindications

Equipment and Methodology

Cycle ergometerTreadmill ergometer

Airflow or volume transducers1.Pneumotachograph2.Mass flow sensor3.Pitot tube flowmeter4.Turbine volume transducer

Gas analyzersMass spectrometer: measure O2, CO2, N2Separate analyzer for O2, CO2

Gas exchange measurement: VO2 and VCO2VO2 = [(Vi . FiO2) - (Ve . FeO2)]/t

Vi is not commonly measured, N2 is neither absorbed nor discharged from the capillaries Vi . FiN2 = Ve . FeN2

Vi = Ve . FeN2/FiN2

because FiCO2 in room air is practically zero and may be safely ignored in the calculation:Vco2 = [Ve . FeCO2]/t

Bag collection method:Douglas bagMixing chamberBreath-by-breath mode

Exercise Testing ProtocolsMaximal incremental cycle ergometry protocolsMaximal incremental treadmill protocolsConstant work rate protocol

Maximal incremental cycle ergometry protocolsIET protocol

3 minutes of rest, 3 minutes of unloaded pedaling the incremental phase of exercise every minute (5 to 25 W/minute) until the patient reaches volitional exhaustion or the test is terminated by the medical monitor

Ramp protocol increase the work rate continuously, usually every 1 to 2 seconds

in a ramplike fashionStandardized exponential exercise protocol

work rate is increased exponentially by 15% of the previous workload every minute

Maximal incremental treadmill protocolsBruce protocol:

the starting point (ie, stage 1) is 1.7 mph at a 10% grade (5 METs). Stage 2 is 2.5 mph at a 12% grade (7 METs). Stage 3 is 3.4 mph at a 14% grade (9 METs). This protocol includes 3-minute periods to allow achievement of a

steady state before workload is increased.Modified Bruce protocol

2 warmup stages, each lasting 3 minutes. The first is at 1.7 mph and a 0% grade, the second is at 1.7 mph and a 5% grade

Balke protocol - speed is kept constant at 3.3 mph, and elevation is increased by 1% every minute

Modified Balke protocol - fixed treadmill speed is chosen and the treadmill grade is increased by a constant amount each minute

Naughton, Weber, and Asymptomatic Cardiac Ischemia Pilot (ACIP) study protocols, all of which start with less than 2 METs at 2 mph and increase in 1- to 1.5-MET increments between stages.

Constant work rate protocolTreadmill or cycle ergometry exercise at levels approximating the subject’s usual daily activities (e.g., up

to 3.0 mph on a treadmill, or up to 50 W on a cycle ergometer). A constant work rate may be performed about 1 hour after an IET. This test should involve at least 6 minutes of continuous exercise. Alternatively, using 50 to 70% of the maximal work rate achieved

during an incremental exercise, a constant work rate test for 5 to 10 minutes often achieves about 70 to 90% of O2max achieved during IET.

Constant work rate protocolUsed: monitoring response cardiopulmonary rehabilitation,

bronchodilators, LVRS, medical devicesanalysis of exercise tidal flow–volume loops and dynamic

hyperinflation, gas exchange kinetics, and validation of pulmonary gas exchange during incremental exercise testing

Patient safetyRelatively safe 0 – 5 / 100000 exercise test (AHA)Veteran Affairs Health Care System exercise laboratories: an

event rate of 1.2 per 10000 tests (MI, VT)

Normal

Cardiomyopathy

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