Data Processing From Indirect Calorimetry: Recommendations and Guidelines

Data Processing From Indirect Calorimetry: Recommendations and Guidelines

Data Processing From Indirect Calorimetry: Recommendations and Guidelines Robert A. Robergs, Ph.D., FASEP, EPC Exercise Physiology Laboratories, Exercise Science Program, University of New Mexico Maximal Oxygen Consumption (VO2max) VE FEO2 FECO2 VO2 VO2max Cardiorespiratory limitations A.V. Hill Time or Intensity Background No universally recommended procedures for processing VO2 data from breath-by-breath indirect calorimetry, or from time averaged systems. No standardized criteria or recommended methods for detecting either of a VO2 plateau, the maximal rate of oxygen consumption (VO2max), or a peak VO2 in the absence of a VO2 plateau (VO2peak). Increasing use of breath-by-breath indirect calorimetry in education, research and professional practice The lack of any objective criteria to follow when processing decreases the validity of measurement. Challenges How do researchers in exercise physiology currently collect and process data? What causes the noise in breath-by-breath VO2 data?

Should this noise be reduced? How should this noise be reduced? What is a VO2 plateau? How can a VO2 plateau be objectively determined? What is VO2max? What is VO2peak? How can VO2max and VO2peak be objectively determined? How do researchers in exercise physiology currently collect and process data? Survey conducted over internet International sport science email discussion list (www.sportsci.org) n = 75 Breath-by-breath = 48% Time averaged mixing chamber = 25% Either depending on purpose = 27% Data processing = 30 s (38%), 60 s (18%), 20 s (11%), a moving average of 5-11 breaths (10%), 15 s (8%) and the middle 5 of 7 breaths (7%), other (8%) Check for VO2 plateau = 93% No distinction between VO2max or VO2peak = 76% VO2 Plateau criteria < 150 mL/min (34%) < 2 mL/kg/min (27%) subjective visual (18%) other (19%) Secondary criteria = attainment of age predicted HRmax (53%), RER > 1.10 (49%) or RER > 1.15 (27%), RPE > 17, 18 or 19 (20%) Why these methods used? = own beliefs (32%), what they were taught (26%), what they read in research articles (22%), tradition (13%) and the influence of their colleagues (7%) VO2 (L/min) What causes the noise in breath-by-breath VO2 data? 3.5 3.0 2.5

2.0 1.5 1.0 VE STPD (L/min) 2.17 0.3 L/min, with a range of 1.4 3.3 L/min 70 55 40 25 10 Predicted VO2 (L/min) Variability 96 % explained by a two-factor model of VE and FEO2 3.5 3.0 Pred VO2 = 0.9572(Meas VO2) + 0.0898 R2 = 0.9572 SEE = 0.059 L/min) 2.5 2.0 1.5 1.0 0.5 0.0 0.0 3.5 0.5

1.0 1.5 2.0 2.5 3.0 Measured VO2 (L/min) 3.0 VO2 (L/min) 4.0 2.5 2.0 1.5 1.0 Measured Predicted 0.5 0.0 0 2 4 6 8 Time (min)

10 12 14 3.5 4.0 VO2 (L/min) 2.5 5%error 2.0 1.5 1.0 0.5 0.0 0 2 4 6 8 Time (min) 10 12 14

Should this noise be reduced? SIM How should this noise be reduced? 4.5 4.0 3.5 VO2 (L/min) VO2 (L/min) 4 a=bb 3.0 2.5 2.0 1.5 Time Averaging b=15 s 3 2 40 0.5 60 s 0 5

10 15 0 20 0 Time (min) 4 5 10 15 20 Time (min) 4 c=30 s d=60 s Breaths 30 0.0 20 30 s 10

15 s 3 VO2 (L/min) VO2 (L/min) e 1 1.0 2 1 3 0 0 2 0 5 10 15 Time (min) 20 10 Time (min)

1 0 5 0 0 5 10 15 Time (min) 20 15 20 4.5 4.0 Breath Averaging b=5 breaths 4 3.0 2.5 2.0 1.5 1.0

3 2 1.75 1 0.5 0.0 0 0 5 10 15 20 0 Time (min) 10 15 20 Time (min) 4 c=11 breaths 3 VO2 (L/min)

VO2 (L/min) 4 5 2 1 d=21 breaths 3 0 5 10 15 Time (min) 20 1.50 1.25 21 breaths 1.00 0.75 11 breaths 0.50 5 breaths

0.25 bb 0.00 0 2 5 10 Time (min) 1 0 Time Interval (min) 3.5 VO2 (L/min) VO2 (L/min) 5 a=bb 0 0 5 10

15 Time (min) 20 15 20 VO2 (L/min) 4 a muscle 3 Digital Filtering 2 1 4 b 3 3 2 1 2 1

0 0 4 4 VO2 (L/min) cardiovascular c ventilation VO2 (L/min) VO2 (L/min) 4 VO2 (L/min) 0 d 3 2 e 3 2 1

1 0 0 0 50 100 150 Data Points 200 250 0 50 100 150 Data Points 200 250 What is a VO2 plateau? V O2 (m L/m in ) 3750

V O2 (m L/m in) 4000 3500 3250 2750 12 3500 linear regres s ion 3000 13 14 15 16 17 18 Time (min) 3000 VO2 plateau at VO2max 2500 2000

initial deviation from linearity 1500 1000 500 exercise rest 0 0 2 4 6 8 10 Time (min) 12 14 16 18 What is VO2max or VO2peak? VO2 (L/min) 5 4

3 2 1 0 0 2 4 6 8 10 12 Time (min) 14 16 18 Data Example treadmill running VO2 (mL/min) 4000 3600 3200 2800 2400 2000 10

11 12 13 Time (min) 14 15 Custom Programming Example Conclusions Clear rationale for processing breath-by-breath VO2 data to decrease noise. Processing best done by digital filtering Still formulating and debating criteria and methods to quantify VO2 plateau, VO2max, VO2peak In the absence of a VO2 plateau, what are valid criteria to use to verify a true VO2max? Thank you

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