Use of indirect calorimetry during cardiopulmonary exercise testing

1. Cardiopulmonary
Exercise Testing

2. Why?
• To assess functional capacity
• To measure optimal performance
• To determine factors limiting performance
• To judge ability to return to normal activity (post-
injury/illness)
• To provide specific comparisons to performance standards

3. Types of Tests
Incremental Exercise Tests Indirect Exercise Tests
Maximal tests
Submaximal tests
Field Tests
Cooper Run
6 Minute Walk test
Step tests
Continuous tests
Discontinuous tests

4. Maximal tests
What type of protocol?
What measurements?
What mode of exercise?
Treadmill
Cycle ergometer
Upper Body ergometer
Continuous v discontinuous
Short v Long
VO2, VCO2, RER, VE
Heart Rate
Blood Lactate
RPE
SmO2

5. VO2 measurement

6. Assessing VO2max
 Single best estimate of CR Fitness
 Amount of oxygen consumed depends upon:
– Ability to transport oxygen
– Ability to extract/use oxygen
(HR x SV) x a-vO2difference
FICK EQUATION

7. Measuring Energy Expenditure:
Direct Calorimetry
 Substrate metabolism efficiency
– 40% of substrate energy  ATP
– 60% of substrate energy  heat
 Heat production increases with energy production
– Can be measured in a calorimeter
– Water flows through walls
– Body temperature increases water temperature

9.  Pros
– Accurate over time
– Good for resting metabolic measurements
 Cons
– Expensive, slow
– Exercise equipment adds extra heat
– Sweat creates errors in measurements
– Not practical or accurate for exercise
Measuring Energy Expenditure:
Direct Calorimetry

10.  Estimates total body energy expenditure based on O2
used, CO2 produced
– Measures respiratory gas concentrations
– Only accurate for steady-state oxidative metabolism
Measuring Energy Expenditure:
Indirect Calorimetry
Open Circuit Spirometry – The most common method of
indirect calorimetry performed in health and research
settings

11. Open Circuit Spirometry
– In open-circuit spirometry, the subject breathes
room air in and is thus “OPEN” to the environment
– Expired air is prevented from leaving the
mouthpiece through a valve
– The % of O2 and CO2 in inspired and expired air is
evaluated by the analyzers (which must be
calibrated) to determine O2 use and CO2 production

13. Metabolic Equipment
 Mouthpiece/nose clip or mask
– Allow air in, prevent air loss
 O2 and CO2 analyzer
 Connecting hoses
 Pneumotach sensor
 Calibration gas tank and volume
cylinder

14. Common Variables
Measured

15. Measurements - VO2 and VCO2
VO2: volume of O2 consumed per minute
– Rate of O2 consumption
– Volume of inspired O2 − volume of expired O2
VCO2: volume of CO2 produced per minute
– Rate of CO2 production
– Volume of expired CO2 − volume of inspired CO2

16.  Analyzers measure EXPIRED O2 and CO2
 V of inspired O2 may not = V of expired CO2
 V of inspired N2 = V of expired N2
Measurements - VO2 and VCO2

17.  Haldane transformation
– Unfortunately, VE does not = VI
– Allows V of inspired air (unknown) to be directly calculated
from V of expired air (known)
– Based on constancy of N2 volumes
– VI = (VE x FEN2)/FIN2
– VO2 = (VE) x {[1-(FEO2 + FECO2) x (0.265)] − (FEO2)}
Measurements - VO2 and VCO2

18. Measurements - VO2 and VCO2
 A volume of O2 consumption
relative to unit of body mass and
time expressed as ml/kg/min
 Used for weight-bearing
modalities
 A discrete volume of O2
consumption in reference to
time expressed in L/min or
ml/min
 Used for nonweight-bearing
modalities
Absolute VO2 & CO2 Relative VO2 & CO2

19.  Respiratory exchange ratio (RER)
– Ratio between rates of CO2 production, O2 usage
– RER = VCO2/VO2
 O2 usage during metabolism depends on type of fuel
being oxidized
– More carbon atoms in molecule = more O2 needed
– Glucose (C6H12O6) < palmitic acid (C16H32O2)
Measurements - RER

20.  RER for 1 molecule glucose (CHO) = 1.0
– 6 O2 + C6H12O6  6 CO2 + 6 H2O + 32 ATP
– RER = VCO2/VO2 = 6 CO2/6 O2 = 1.0
 RER for 1 molecule palmitic acid (Fats) = 0.70
– 23 O2 + C16H32O2  16 CO2 + 16 H2O + 129 ATP
– RER = VCO2/VO2 = 16 CO2/23 O2 = 0.70
Measurements - RER

21. Measurements - RER

22. Measuring Energy Expenditure:
Indirect Calorimetry Limitations
 CO2 production may not = CO2 exhalation
 RER inaccurate for protein oxidation
 RER near 1.0 may be inaccurate when lactate
buildup > CO2 exhalation
 Gluconeogenesis produces RER <0.70

23.  Heart Rate (HR) = measured in beats/min
– an indirect measure of exercise intensity
– Incraeses linrealy during exercise
– ranges from 40’s to 200 b/min
 Blood Pressure (BP) = measured in mmHg (Systolic
BP/Diastolic BP
– SBP increases with exercise, DBP remains the same
 Electrocardiogram (ECG) = measurement of heart
rhythm
Measurements – Cardiovascular

24.  Tidal Volume (VT) = volume of air inspired/expired
per breath (mL or L)
 Breathing Frequency (FB) = number of breaths (per
minute)
 Minute Ventilation (VE) = volume of air expired per
minute (L/min)
Measurements – Ventilatory

25.  Blood Lactate (La-) = measured in mmol?L of blood
– Blood La- is a measure of anaerobic metabolism use
– Typically sampled from venous blood sample using
fingerprick methods
– Remains stable (2 mmol/L) during moderate exercise
and increases exponentially with higher intensity
(above LT)
Measurements – Metabolic

26.  Muscle Oxygen Saturation (SmO2) =
– The measurement of SmO2 takes place in the capillaries
of the muscle, where O2 is being consumed.
– SmO2 is a good measure of O2 supply v. demands in
muscle.
 Muscle Total Hemoglobin (tHgb) =
– Measure of total blood flow to a tissue (muscle)
Measurements – Metabolic

27.  Ratings of Perceived Exertion (RPE) = A scale to
assess a subjects perceived estimate of difficulty of
an activity.
 Pain scales = a scale used to assess subject pain
(typically local) during an activity.
Measurements – Cognitive scales

29. Wong Baker Faces Scale Angina Scale

30. Performing
VO2max Tests

31. Time Abs.VO2 Abs.VCO2 Rel.VO2 Rel.VCO2 RER METS Calories VE HR
sec L/min L/min ml/kg/min ml/kg/min kCal/min L/min bpm
:20 0.316 0.261 5.108 4.225 0.827 1.459 1.579 8.317 119.061
:40 0.779 0.604 12.606 9.773 0.775 3.602 3.896 16.397 126.217
1:00 0.994 0.748 16.084 12.101 0.752 4.595 4.971 18.327 130.455
1:20 1.549 1.037 25.054 16.782 0.67 7.158 7.744 25.943 144.894
1:40 1.396 1.025 22.586 16.582 0.734 6.453 6.981 23.475 147
2:00 1.512 1.107 24.466 17.906 0.732 6.99 7.562 25.211 146.791
2:20 1.957 1.451 31.651 23.473 0.742 9.043 9.783 34.244 152.718
2:40 1.481 1.151 23.954 18.627 0.778 6.844 7.404 28.2 157.643
3:00 1.849 1.433 29.914 23.174 0.775 8.547 9.246 33.598 153.11
3:20 1.66 1.292 26.848 20.9 0.778 7.671 8.298 31.369 157.84
3:40 1.972 1.575 31.906 25.476 0.798 9.116 9.862 34.519 162.935
4:00 1.869 1.512 30.228 24.459 0.809 8.637 9.343 35.06 160.694
4:20 2.198 1.795 35.549 29.042 0.817 10.157 10.988 39.977 170.435
4:40 2.184 1.827 35.328 29.55 0.836 10.094 10.92 40.889 168.324
5:00 2.181 1.82 35.287 29.444 0.834 10.082 10.907 42.494 170.595
5:20 2.552 2.107 41.277 34.088 0.826 11.793 12.758 47.64 172.901
5:40 2.237 1.87 36.184 30.242 0.836 10.338 11.184 42.423 165.552
6:00 2.574 2.188 41.642 35.391 0.85 11.898 12.871 49.542 175.971
6:20 2.825 2.454 45.692 39.698 0.869 13.055 14.123 54.444 176.496
6:40 2.724 2.38 44.068 38.505 0.874 12.591 13.621 54.667 187.5
7:00 3.023 2.641 48.899 42.716 0.874 13.971 15.114 57.622 182.535
7;20 3.076 2.754 49.76 44.543 0.895 14.217 15.38 60.527 172.171
7;40 3.013 2.675 48.747 43.265 0.888 13.928 15.067 58.055 184.078
8:00 2.874 2.617 46.496 42.341 0.911 13.285 14.372 59.16 186.395
8:20 2.153 1.944 34.828 31.439 0.903 9.951 10.765 44.443 193.06
8:40 3.637 3.34 58.832 54.023 0.918 16.809 18.184 74.142 198.722
9:00 3.495 3.294 56.542 53.293 0.943 16.155 17.477 72.452 194.531
9:20 3.92 3.721 63.405 60.189 0.949 18.116 19.598 80.372 207.85
9:40 3.595 3.502 58.151 56.644 0.974 16.615 17.974 76.321 198.181
10:00 3.926 3.851 63.504 62.298 0.981 18.144 19.628 82.236 198.883
10:20 4.151 4.098 67.152 66.291 0.987 19.186 20.756 87.111 195.581

32. 0
10
20
30
40
50
60
70
80
Rel VO2 v Time
0
50
100
150
200
250
HR v Time

34. Was it really maximal?
 Maximal oxygen consumption = single highest oxygen
consumption elicited among different modes of exercise
 Peak oxygen consumption = highest oxygen consumption
for a specific type of exercise
– Related to involved muscle mass and type of training

35. VO2max Criteria
 Plateau of oxygen consumption and HR despite an increase
in power level!
– No greater than 150 mL.min-1
 RER > 1.05 or more
 High Blood Lactate (> 8 mM)
 RPE > 17-18
 Reaching a previously MEASURED max HR
 Failure of HR to rise with increased intensity
 Subject exhaustion

36. Normal Values for VO2max (ml/kg/min)
Age (years) Very High High Good Average Fair Low
20-29 >61 53-61 43-52 34-42 25-33 <25
30-39 >57 49-57 39-48 31-38 23-30 <23
40-49 >53 45-53 36-44 27-35 20-26 <20
50-59 >49 43-49 34-42 25-33 18-24 <18
60-69 >45 41-45 31-40 23-30 16-22 <16
20-29 >57 49-57 38-48 31-37 24-30 <24
30-39 >53 45-53 34-44 28-33 20-27 <20
40-49 >50 42-50 31-41 24-30 17-23 <17
50-59 >42 38-42 28-37 21-27 15-20 <15
60-69 >39 35-39 24-34 18-23 13-17 <13
MALES
FEMALES

37. Estimating VO2max

38. ACSM Equation components
 Rest = 3.5 ml/kg/min
 Horizontal = m/min x 0.1 ml O2 per m/min
– 0.1 ml of O2 to transport each kg of body mass per meter of
horizontal distance
 Vertical = grade (fraction) x m/min x 1.8
– 1.8 ml of O2 per kg of body mass for each meter of vertical
distance

39. Distances
 1mile=1.62km
 1km=0.62mile
 1mile=5280feet
 1m=3.28ft
 1inch=2.54cm
Speeds
 1mph=26.8m/min
 1mph=1.62km/hr
 1km/hr=0.62mph
Weight
 1lb = .454kg
Work
 1 MET= 3.5ml/kg/min

40. Walking Equation
VO2(ml/kg/min) = 0.1 (speed) + 1.8 (speed) (grade) + 3.5
– used for speeds of 50-100 m/min or 1.9-3.7 mph
– Ex. 5% grade = .05

41. Running Equation
VO2 (ml/kg/min) = 0.2 (speed) + 0.9 (speed) (grade) + 3.5
- Resting = 3.5 ml/kg/min
- Horizontal = m/min x 0.2 O2 per m/min
- Vertical = grade (fraction) x m/min x 0.9
(used for speeds >80 m/min if truly jogging)