Respiratory exchange ratio 119

Alveolar ventilation supplies O2 to the bloodstream while alveolar capillary perfusion provides alveolar gas with COj. Resting individuals consume approximately 250 mL 02/min and produce approximately 200 ml. COi/min because, stoichiometrically, metabolic processes require a greater supply of O, than the quantity of CO2 produced. Defining the respiratory exchange ratio, R, as... 

The respiratory exchange ratio (usually abbreviated, RQ or R) should be known but, in practice, it makes little difference unless very high accuracy is required. 

DEWAR STRUCTURES KEKULE STRUCTURES RESONANCE STABILIZATION ENERGY RESPIRATORY BURST OXIDASE NADPH OXIDASE RESPIRATORY EXCHANGE RATIO Restricted rotation,... 

Studies of the respiratory quotient or respiratory exchange ratio (RER) indicate a metabolic shift in CR rats depending on food availability, while there is little change in AL rats [21,42]. Figure 7 illustrates daily variations of RER with dietary regimen. Analysis of the food composition indicates an expected average value of RER of 0.89. RER in AL rats is 0.89 0.02 over a 24-hour period and is relatively more constant than that in CR rats, indicating that AL rats metabolize a constant ratio of carbohydrate and lipid over 24 hours [21, 42]. In contrast, CR animals metabolize more carbohydrate... 

Fig. 7. Respiratory exchange ratio of male F344 rats at 18 months of age. Calorically restricted rats were fed just before turning off the light (arrow). The light was off from hours 0 to 12 and on from hours 12 to 24. Adapted from reference 21.

The quantitative analysis of oxidation of fuels shows that when most carbohydrates are oxidized, the ratio of carbon dioxide produced to oxygen consumed is 1. On the other hand, this ratio, which is called the respiratory quotient (RQ) or the respiratory exchange ratio, is -0.7 when fatty acids are oxidized. The measurements of O2 consumption and CO2 emission only indicate which fuels are being oxidized on average by the whole body and do not necessarily reflect which fuel is being used selectively by particular cell types or tissues. As noted in Chap. 11, the synthesis of triglycerides raises the RQ above 1. 

Equation 4.7 uses the definition of the respiratory exchange ratio, R = VcqjA qj. which usually has a value of /f 0.8 for VJQ = 1. It also replaces the end capillary concentration with the systemic arterial value, assuming equilibration. From Eq. 4.7, the extreme limits of VJ Q, men-... 

Respiratory exchange ratio Is the CO2 output divided by the oxygen uptake. At times when the excretion of COj matches its production, the respiratory exchange ration equals the RQ. If excretion exceeds production, the respiratory exchange ratio exceeds the RQ In the early phases of hyperventilation, the respiratory exchange ratio may approach 2. 

Colombani et al. incorporated a double-blind crossover design to study the general metabolic impact of ARG aspartate supplementation in 14 endurance-trained athletes, using 15 g of ARG aspartate or placebo for 14 days before a marathon run. The authors foimd no obvious metabolic benefit, including no differences in the respiratory exchange ratio, cortisol, insulin, ammonia, or lactate levels related to the supplementation of ARG aspartate. ... 

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