1. Energy Expenditure

2. Direct Calorimetry zAll metabolic processes produce heat zHuman calorimeter - closed system zMonitored heat output

3. Direct Calorimetry

4. Indirect Calorimetry zEstimate energy expenditure from O 2 uptake z5 kcal/L of O 2 consumed is liberated

5. Closed-Circuit Spirometry zClosed system of 100% O 2 - Rebreathe zCanister of KOH absorbs expired CO 2 zO 2 consumption = VO 2i - VO 2f zEffective for resting and light exercise

6. Open-Circuit Spirometry zInhale ambient air w/ constant composition (20.93% O 2, 0.03% CO 2, 79.04% N 2 ) zO 2 consumption = inspired O 2 - expired O 2

7. Open-Circuit Spirometry zPortable zBag Technique zComputerized Instrumentation

8. Open-Circuit Spirometry

9. Respiratory Quotient (RQ) Assumption: Exchange of O 2 and CO 2 measured at the lungs reflects the actual gas exchange from nutrient catabolism in the cell zsteady-rate conditions

10. Respiratory Quotient (RQ) zDetermine magnitude & type of food metabolized z% contribution of lipids and CHO zChemical composition of various CHO, fats, and proteins varies

11. Respiratory Quotient (RQ) zQuantity of CO 2 produced / O 2 consumed zRQ = VCO 2 / VO 2 zVaries depending on the composition

12. Respiratory Quotient (RQ) zRQ = CO 2 produced / O 2 consumed zCHO yC 6 H 12 O 6 + 6 O 2  6 CO 2 + 6 H 2 O zRQ = 6 CO 2 / 6 O 2 = 1.0

13. Respiratory Quotient (RQ) zLipid - C 16 H 32 O 2 + 23 O 2  16 CO 2 + 16 H 2 O zRQ = 16 CO 2 / 23 O 2 = 0.696 zRQ  0.70

14. Respiratory Quotient (RQ)

15. Protein (Albumin) C 72 H 112 N 2 O 22 S + 77 O 2  63 CO 2 + 38 H 2 O + SO 3 + 9 CO(NH 2 ) 2 zRQ = 63 CO 2 / 77 O 2 = 0.818 zRQ  0.82

16. Respiratory Quotient (RQ) However, impossible to determine proteins contribution to RQ. Why? zNot completely oxidized zAs a result...

17. Calulate the Nonprotein RQ zIgnore protein oxidation zCalculate only CHO and Fat oxidation

18. Limitations of RQ zCannot calculated protein use accurately zAssume body’s O 2 content remains constant and CO 2 exchange is proportional to its release from cells zAt or near exhaustion   CO 2 2 0 excess lactate zproduction of glucose in liver from AA and fats  RQ < 0.70

19. Respiratory Exchange Ratio (RER) zRQ assumption holds true only in steady- rate conditions zIdentical calculation to RQ zreflects gas exchange only

20. Calulate the Nonprotein RQ zFor each gram of excreted N (urea): - 4.8 L CO 2 is produced - 6.0 L O 2 is consumed If a subject: - consumes 4.0 L O 2 - produces 3.4 L CO 2 - excretes 0.13 g of N

21. Nonprotein RQ zDetermine CO 2 produced: - 4.8 L CO 2 /g * 0.13 g = 0.62 L zDetermine O 2 consumed: - 6.0 L O 2 /g * 0.13 g = 0.78 L zDetermine nonprotein CO 2 produced: - 3.4 L - 0.62 L = 2.78 L

22. Nonprotein RQ zDetermine nonprotein O 2 consumed: - 4.0 L - 0.78 L = 3.22 L zOverall nonprotein RQ: - 2.78 / 3.22 = 0.86 zDetermine thermal equivalents (table)

23. How much food was metabolized for energy? zKnown: 3.22 L O2 consumed zCalculated nonprotein RQ: 0.86 zTable look-up - 0.62 g CHO/L O 2 - 0.25 g lipid/L O 2

24. How much food was metabolized for energy? zGrams of CHO metabolized: - 3.22 L x 0.62 g/L = 2.00 grams zGrams of lipid metabolized: - 3.22 L x 0.25 g/L = 0.80 grams

25. How much food was metabolized for energy? zHow many calories were metabolized? - CHO: 2 g * 4 kcal/g = 8.0 kcal - lipid:0.8 g * 9 kcal/g = 7.2 kcal - total:15.2 kcal ztypically assume: 40:60 lipid to CHO ratio (4.825 kcal/L O 2 )