Cardiopulmonary Exercise Testing (CPET)

1. Cardiopulmonary Exercise Testing (CPET) Pathophysiologic Limitations and Exercise Prescription Dr. Scotty Butcher, PhD, BSc(PT), CSCS, RCEP University of Saskatchewan scotty.butcher@usask.ca No conflicts of interest

2. Overview • Overview of exercise limitations • Cardiovascular limitations • Metabolic limitations • Ventilatory limitations • Clinical exercise prescription

3. CPET Interpretation • Was the test maximal? • Was RER ≥ 1.1? • HR > 90% predicted max? • Patient exhaustion? • Was there a plateau in VO2? • Dyspnea score >5? • Was there evidence of a ventilatory limitation • (i.e. Max exercise VE ≥ Predicted MVV)? STEP 1. STEP 2. What was the exercise limitation(s)? Other 1. Leg/Back Pain 2. Cardiac Concern (i.e. ST depression etc) 3. HR < max predicted 4. RQ < 1.1 5. Dyspnea score <5 • Cardiovascular • HR ~ max predicted • RQ ≥ 1.1 • Exhaustion • Max VE < Pred MVV • Dyspnea score >5 • O2pulse <90% pred • Pulmonary • Max VE ≥ Pred MVV • Exp flow limitation • Hyperinflation • SpO2 < 88% • HR < max predicted • RQ < 1.1 • Dyspnea score >5 STEP 3. Pathological or Physiological?

4. PHYSIOLOGIC EXERCISE AND ACTIVITY LIMITATIONS • Cardiac/Cardiovascular • Metabolic and/or muscle • Fatigue • Strength/Power/Endurance • Ventilation • ↑ Ventilatory Requirement &/or • ↓ Ventilatory Capacity • Tidal volume &/or flow constraint

5. Cardiovascular Limitations • May be ‘normal’ • Heart rate > 90% of predicted maximum • O2pulse = indirect marker of SV • will vary with varying fitness • Associated with: • Metabolic Limitations • (Near) Maximal patient effort

6. Metabolic Limitations • Respiratory exchange ratio (RER) = VCO2/VO2 • RER > 1.10 • Indication of impending muscle fatigue • VO2 and work rate should NOT be used to determine a maximal response • will vary with varying fitness

7. Respiratory Limitations • Gas exchange limitations • Exercise-induced hypoxemia • Ventilation limitations

8. Exercise-induced hypoxemia • Decrease in SPO2 > 4% considered clinically significant • Most testing centers will allow a decrease to 80 – 86% before stopping testing • Decrease in SPO2 contributes to exercise intolerance, but is not by itself usually a limiting factor

9. Respiratory Limitations • Gas exchange limitations • Exercise induced hypoxemia • Ventilation limitations • Ventilatory requirements approach capacity • Reduced capacity? • Increased requirements?

10. Ventilatory Reserve in Lung/Airways Disease Predicted Maximum Ventilation (MVV) (35 x FEV1) FEV1 = 1s forced expired volume . Should be 30% VE reserve . VE . VCO2 Exercise Intensity

11. EXERCISE FLOW-VOLUME IN COPD Limitation on ventilation (tidal volume and flow constraint) Healthy COPD Flow Volume Why is breathing at high lung volumes such a problem? ↑ work of breathing EELV Dynamic Hyperinflation

12. Ventilatory Reserve in Athletes Predicted Maximum Ventilation (MVV) (35 x FEV1) FEV1 = 1s forced expired volume . Should be 30% VE reserve . VE . VCO2 Exercise Intensity

13. WHEN DEMAND EXCEEDS CAPACITY Limitation on ventilation (tidal volume and flow constraint) Flow Volume Why is breathing at high lung volumes such a problem? ↑ work of breathing EILV EELV

14. Elite Male Athlete Johnson et al. 1991

15. AGE Johnson et al. 1991

16. Female subjects x = 48 ml/kg/min < 56 ml/kg/min x = 63 ml/kg/min > 57 ml/kg/min McClaran et al. JAP. 1998;84:1872-1881

17. Case 22 yr old female BMI: 26 (but muscular with low body fat) Severe dyspnea on exertion; “diagnosed” with exercise-induced asthma Currently taking salbutamol before and after exercise. She says it doesn’t help FEV1 106% pred. FVC 102% pred. Very active – elite cross country skier No CV history or significant family history

18. Peak Exercise Data .

19. Elite Female X-Country Skier 100% VO2max (53 ml/kg/min) 50% VO2max

20. CPET Interpretation STEP 3. Pathological or Physiological? • Was the test maximal? • Was RER ≥ 1.1? • HR > 90% predicted max? • Patient exhaustion? • Was there a plateau in VO2? • Dyspnea score >5? • Was there evidence of a ventilatory limitation • (i.e. Max exercise VE ≥ Predicted MVV)? STEP 1. STEP 2. What was the exercise limitation(s)? Other 1. Leg/Back Pain 2. Cardiac Concern (i.e. ST depression etc) 3. HR < max predicted 4. RQ < 1.1 5. Dyspnea score <5 • Cardiovascular • RQ ≥ 1.1 • HR ~ max predicted • Exhaustion • Dyspnea score >5 • Max VE < Pred MVV • Pulmonary • Max VE ≥ Pred MVV • Exp flow limitation • Hyperinflation • SpO2 < 88% • HR < max predicted • RQ < 1.1 • Dyspnea score >5

21. Exercise Prescription from CPET • Based on CPET results, exercise rehabilitation can be more efficient • Three example methods: • Anaerobic Threshold (AT) Continuous • AT intervals • High Intensity Intervals (peak power)

22. Anaerobic Threshold • Definition: • Anaerobic energy production accelerates to supplement aerobic energy production • H+ production exceeds the rate of removal (and consequently, H+ buffering begins) • Why is it important? • Good predictor of aerobic or endurance capacity • Usually an optimal training intensity for cardiovascular adaptation

23. Anaerobic Threshold • Measurement: • Common method is “V-slope” method • V-slope graphs VCO2 vs VO2

24. VCO2 plotted against VO2 (V-slope method) VCO2 (L/min) VO2 (L/min)

25. Anaerobic Threshold • Measurement: • Common method is “V-slope” method • V-slope graphs VCO2 vs VO2 • Commercial software often underestimates AT • Not unusual to see automatic selection of AT at an RER 0.85 or less • Better method: “dual criteria” or “ventilatory equivalent” methods

26. Anaerobic Threshold • Criteria for determining AT using dual criteria: • A nadir in VE/VO2 followed by an incremental increase • A plateau in VE/VCO2 • A respiratory exchange ratio around 1.0 (0.98 – 1.02)

27. Anaerobic Threshold Plateau in VE/VCO2 Nadir RER ~ 1.0 ~40 – 60% Exercise Intensity

28. Why train at AT and not a % of max? IT = individualized at AT ST = standard training at 50% Vallet 1997 Eur Respir J 10:114-122 (COPD patients)

29. Exercise prescription from CPET • Frequency: 3 – 5 times per week • Intensity (examples of methods): • Continuous at, or slightly below, AT • AT Intervals: alternating 10% above : 10% below AT for 2-5 minutes on : 2-5 minutes off • Peak Power intervals: alternating at 100% peak work rate for 1-2 minutes and at 20% for 1-2 minutes • Time: 20 – 30 minutes • Type: large muscle mass activity (walking/running, swimming, cycling)

30. SUMMARY • Comprehensive CPET can be used diagnostically to determine functional physiological limitations • Individualized exercise rehabilitation intensity to optimize outcomes

31. Acknowledgements • Collaborators • Dr. Don Cockcroft • Dr. Jon Farthing • Dr. Phil Chilibeck • Clinicians • Trent Litzenberger • Wendy Verity • Catherine Baule • ICEP Lab • Dr. Darcy Marciniuk • Robyn Chura • Ron Clemens • Madison Yurach • Brendan Pikaluk • Funding Sources:

32. Thank you