Oxygen Uptake

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Oxygen Uptake and Energy Expenditure

• M.Prasad Naidu
• MSc Medical Biochemistry, Ph.D,.

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Objectives

• Understand the meaning and derivation of the
  oxygen uptake measurement and measurement of
  energy expenditure.
• Perform techniques to measure oxygen uptake (O2),
  carbon dioxide production (CO2), and RER.
• Calculate energy expenditure during exercise.

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Aerobic Metabolism
O2
CO2
AIR
LUNGS
CO2
V/Q Lungs
O2
Pulmonary Circulation
Use O2, produce CO2 ATP from CHO, Fats
Heart
Muscle/Tissues
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VO2 Fick Relationship

• VO2 (ml/min) Q(L/min) AVDO2
• Expanded HR SV 1.34 Hb (SaO2 -
  SvO2)
• SV L blood/bt Hb g Hb/100 ml blood
• 1.34 ml O2/gm Hb Saturations in decimal
  equivalent of
• Affects of Heart Disease? Altitude? Lung
  Disease? Training?

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Uses

• Energy expenditure, efficiency, VO2max index of
  fitness, Time course of VO2 in response to work
• Steady state concept

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Important variables for measurement of VO2

• VE or VI, FeO2, FIO2, FI CO 2, FeCO2
• Assumption N2 not produced or used by body
  during exercise

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Convert gas volumes to STPD from ATPS (CCJ Lab
Manual p. 60)

• Standard Temperature Pressure Dry
• Temperature 0 degrees Celsius
• Pressure 760 mmHg (sea level)
• Dry 0 humidity
• Equation 1 
• VSTPD VATPS (Pb - PH2O) /760 273/(oC
  273)
•   Note PH2O under saturated conditions is
  temperature dependent (CCJ, p. 60).
•   Ambient PH2O is obtained as
•  Equation 2
•   Ambient PH2O Saturated PH2O Relative
  Humidity/100

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VO2 Consumption is volume O2 inhaled - volume O2
exhaled

• Equation 3
• VO2 (VI FIO2) - (VE FeO2)
• NOTE VI ? VE unless 100 Carbohydrate oxidized
• Remember C6H12O6 6O2 6H2O 6CO2
• Therefore CO2 / O2 1

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• Haldane Transformation Allows us to calculate
  either VI or VE if only one is known. Based on
  fact N2 is not used or given off by body.
• ? N2 in N2 out
• or
• Equation 4
• VI FI N2 VE FeN2
•  
• Assume FIN2 1 - FIO2 - FICO2
• FEN2 1 - FEO2 - FECO2
•  
• Standard air values FIO2 .2093
• FICO2 .0003
• FIN2 .7904

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Hadane Transformation (cont)

• Rearrange and combine 
• Equation 5
• VI VE (FeN2 / FI N2) or VE VI (FI N2 /
  FeN2) 
•  
• Substitute into VO2 equation if we measure VE
  gives
• Equation 6
• VO2 VE (FeN2 / FI N2) FIO2 - (VE
  FEO2)
• _________VI __________ - __VE ___

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VCO2 Production is volume CO 2 exhaled - volume
CO 2 inhaled

• Equation 7
• VCO2 (VE FECO2) - (VI FICO2)
•  
• Applying Haldane Transformation
• Equation 8
• VCO2 VE FECO2 - VE (FeN2 / FI N2)
  FICO2
• ___ VE __ -__________ VI __________
•  

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Respiratory Exchange Ratio

• Caloric equivalents as function of fuels consumed
  (CCJ, Table 6.1, p 62)
• Equation 9
• RER VCO2 /VO2

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Examples of caloric equivalents and fuels
consumed
RER kcal/L oxygen CHO Fat
0.78 4.776 26 74
0.9 4.924 68 32
1.0 5.047 100 0
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