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OXYGEN UPTAKE

BIOCHEMISTRY

mprasadnaidu
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OXYGEN UPTAKE

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  1. Oxygen Uptake and Energy Expenditure M.Prasad Naidu MSc Medical Biochemistry, Ph.D,.

  2. 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.

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

  4. 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?

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

  6. 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

  7. 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

  8. 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

  9. 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. ˆ 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

  10. Hadane Transformation (con’t) 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 ___|

  11. 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 __________|

  12. Respiratory Exchange Ratio • Caloric equivalents as function of fuels consumed (CCJ, Table 6.1, p 62) Equation 9: RER = VCO2 /VO2

  13. Examples of caloric equivalents and % fuels consumed

  14. THANK YOU

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