Cardiopulmonary Exercise Testing

Transcription

1 Cardiopulmonary Exercise Testing Gregg L. Ruppel, MEd, RRT, RPFT, FAARC Adjunct Professor, Pulmonary, Critical Care and Sleep Medicine Saint Louis University School of Medicine

2 Conflicts of Interest Speaker & consultant, MGC Diagnostics Royalties for PFT textbook, Elsevier Consultant, ndd Medical * This lecture sponsored by

3 Indications for exercise testing Unexplained dyspnea Pre-op assessment CPET Cardiac vs. pulmonary exercise limitation Fitness, impairment disability Cardiopulmonary rehabilitation

4 Treadmill or Cycle Ergometer Treadmill VO 2 max 5-10% higher AT at lower VO 2 Familiar exercise Work dependent on weight Difficult to draw blood Movement artifact in pressure measures and/or SpO 2 Cycle Ergometer V E, HR, Lactate similar Work independent of weight Less movement artifact Easier to draw blood Easier access to chest Can be done semirecumbent

5 Protocol Strategies Incremental Workload changes by a fixed amount at fixed intervals May not allow steady-state to be attained Selection of appropriate intervals important

6 Protocol Strategies Ramp Workload increases continuously at fixed rate Best suited to cycle ergometer with computer control Rate of workload increase must be matched to patient fitness (5-50 watts) To estimate ramp: W = (Pred VO2-300) 100

7 Why Measure VO 2? VO 2 increases linearly with workload in normal subjects (at moderate increments) Wasserman

8 How To Measure VO 2 (Exhaled Gas Analysis) Then Now

9 Airflow / Volume Transducers Volume transducers are lightweight. They can be held in the mouth easily or mounted in a mask.

10 Gas Analyzers O 2 uses zirconium cell or other rapid responding analyzer (mass spectrometer) CO 2 uses infrared analyzer

11 Breath by Breath (BxB) Gas Exchange Phase delay

12 Physiologic Data from Exhaled Gas Measurements* VO 2 max (VO 2 peak) L/min or ml/min (STPD) ml/min/kg (ideal or actual weight?) METS (ml/min/kg 3.5) % of predicted VO 2max VCO 2 and RER Anaerobic (ventilatory) threshold O 2 pulse (poor man s cardiac output) Ventilation (V E, V T, f B, V D /V T ) *in addition to the ECG, blood pressure, etc.

13 What is VO 2 max?

14 VCO 2 and RER Exhaled gas analysis includes measurement of CO 2 production RER = VCO 2 /VO 2 (at the mouth) RER > consistent with maximal effort

15 What Is Anaerobic Threshold*? VO 2 above which anaerobic mechanisms supplement aerobic energy production Increase in lactate in muscle and arterial blood Metabolic acidosis (lactic acidosis) occurs Lactic acid buffered by HCO3 - H + + HCO 3 - CO 2 + H 2 O *also sometimes called the ventilatory threshold

16 Anaerobic (ventilatory) Threshold 38 y/o female cycle ergometer V-Slope Method

17 AT/Predicted Peak VO 2 (as a %)* Men Women Age (yr) Mean 95% LLN Mean 95% LLN * AT decreases with age in men and women, but at a slower rate than predicted peak VO 2 Davis JA, Storer TW, Caiozzo VJ: Prediction of normal values for lactate threshold estimated by gas exchange in men and women. J Appl Cardiol 1997; 76:

18 Heart Rate and VO 2 100% CAD COPD Normal Heart Rate VO 2 100%

19 Cardiac Output and O 2 Pulse CO VO 2 C(a - v)o 2 x 10 SV x HR VO 2 C(a - v)o 2 x 10 VO HR 2 SV x C(a - v)o 2 x 10

20 Cardiac Output and O 2 Pulse Normal O 2 Pulse (VO 2 /HR) COPD CAD Rest Exercise VO 2

21 Ventilatory Responses to Exercise BR = Breathing Reserve May fall because of dynamic hyperinflation (COPD)

22 Maximal Ventilation Breathing Reserve V Emax = 0.7 x MVV or V Emax = 0.7 x (FEV 1 x 40) (50-85% of MVV) BR = MVV - V Emax or BR = (% Pred MVV) (absolute) (per cent) Ventilation limitation: MVV - V Emax 11 L/min

23 Flow Limitation During Exercise IC 53 y/o Male, 67 in, 150 lbs

24 Flow Limitation During Exercise IC

25 V T and V D /V T 38 y/o female cycle ergometer

26 Determining Maximal Effort *** Heart rate > 85-90% of predicted *** End exercise V E 50-85% of MVV or ** SpO 2 < 80% MVV-V Emax < 15L * Metabolic work RER > 1.10 or lactate > 7 * Clinical Opinion of effort or early termination criteria met * = weight o f variable Once a single criterion is met, test is graded maximal

27 Heart Rate Reserve (HRR) 38 y/o female cycle ergometer

28 Breathing Reserve (BR) 38 y/o female cycle ergometer

29 Typical VO 2 Predicted Values For a 40 year old male, 70 inches, 170 lbs Wasserman Jones pred VO 2 = 2773 ml/min treadmill = 3078 pred VO 2 = 3029 ml/min For a 70 year old male, 70 inches, 170 lbs Blackie pred VO 2 = 2280 ml/min treadmill = 2508 ml/min

30 Case Example: Dyspnea on Exertion The patient is a 39 y/o Caucasian female with a history SLE, ILD, and increased pulmonary pressures on echocardiogram. Her chief complaint is increased dyspnea on exertion. An maximal exercise test was performed using 3-4 minute increments and increasing the workload by 25W at each increment (cycle ergometer). PFTs were performed before exercise.

31 Case Example: Dyspnea on Exertion Exercise: BP rest 152/92 BP peak 220/96 HR rest 81 HR peak 157 (87%) SpO 2 rest 96 SpO 2 peak 89 Chest pain No ECG No ST changes; Pulmonary function: FVC 2.19 (59%) FEV (64%) FEV 1 /FVC 89 MVV 114 TLC 3.60 (67%) DLCO 8.40 (39%) (Peak = 50 Watts; Reason for stopping: dyspnea)

32 Case Example: Dyspnea on Exertion Gas Exchange: VO 2 peak ml/min 1122 (55%) VO 2 peak ml/min/kg 17.0 (51%) AT/VO 2 max 34% pred max METs 4.9 V E max L/min 53 Breathing reserve 61 L/min (46% MVV) RER 1.02 O 2 pulse 7.1 (62%) V D /V T 50% A-aDO 2 57 V E /VCO 2 46 (Peak = 50 Watts; Reason for stopping: dyspnea)

33 Case Example: Dyspnea on Exertion Heart Rate Reserve Ventilatory Reserve

34 Case Example: Dyspnea on Exertion % Watts VD/VT Expected Vd/Vt

35 In Summary Measurement of VO 2 overcomes many of the issues with specific exercise protocols VO 2 avoids pitfalls associated with estimates of workload (METS) VO 2 allows measurement of important exercise variables (AT, O 2 pulse, aerobic impairment) VO 2 is relatively easy to measure (BxB) Exhaled gas analysis provides other important parameters (V E, V D /V T, RER)

36 Questions?? Comet c2014 Q2 Lovejoy 2/7/2015