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Oxygen Uptake and Energy Expenditure
M.Prasad NaiduMSc Medical Biochemistry, Ph.D,.
ObjectivesUnderstand 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.
Aerobic Metabolism
O2 CO2 AIR
LUNGS
O2CO2 V/Q Lungs
Pulmonary Circulation
Heart
Muscle/Tissues
Use O2, produce CO2
ATP from CHO, Fats
VO2 Fick RelationshipVO2 (ml/min) = Q(L/min) * AVDO2
Expanded: [HR * SV] * [1.34 * [Hb] * (SaO2 - SvO2)]
SV = L blood/bt [Hb] = g Hb/100 ml blood1.34 = ml O2/gm Hb Saturations in decimal equivalent of %
Affects of: Heart Disease? Altitude? Lung Disease? Training?
Uses:Energy expenditure, efficiency, VO2max index
of fitness, Time course of VO2 in response to work
Steady state concept
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
Convert gas volumes to STPD from ATPS(CCJ Lab Manual p. 60)
Standard Temperature Pressure DryTemperature = 0 degrees CelsiusPressure = 760 mmHg (sea level)Dry = 0% humidityEquation 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
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
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 orEquation 4:VI * FI N2 = VE * FeN2
Assume: FIN2 = 1 - FIO2 - FICO2
FEN2 = 1 - FEO2 - FECO2
Standard air values:FIO2 = .2093FICO2 = .0003FIN2 = .7904
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 ___|
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 __________|
Respiratory Exchange RatioCaloric equivalents as function of fuels
consumed (CCJ, Table 6.1, p 62)
Equation 9: RER = VCO2 /VO2
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