Respiratory Quotient

Introduction

The process of breaking down the respiratory substrate to liberate energy is known as respiration.

• Aerobic and anaerobic respiration are the two basic operational elements of cell respiration, with aerobic respiration requiring the presence of oxygen and anaerobic respiration not

• Glucose, a 6-carbon molecule, is the most frequent respiratory substrate. Glycolysis, the TCA cycle, the electron transport chain, and oxidative phosphorylation are all used to break down the substrate

• Cells may make and store ATP during these cycles, and carbon dioxide is produced as a by-product. Understanding the quantities of carbon dioxide generated by various substrates is critical since hazardous levels may be harmful to the organism

• Healthcare experts might advise a patient to change his or her diet, especially if he or she has pulmonary or hepatic disease, in order to boost CO2 release and reduce respiratory weariness, as well as use it as a prognostic factor

The respiratory quotient (RQ) is the difference between the volume of carbon dioxide exhaled and the volume of oxygen received during breathing. When estimated from carbon dioxide generation to oxygen absorption, it is a dimensionless quantity employed in a computation for basal metabolic rate. Oxygen uptake is a type of indirect calorimetry that is measured directly at the tissue or mouth with a respirometer. RQ = (Volume of carbon dioxide eliminate/Volume of oxygen consumed)

Respiratory Exchange Ratio

The respiratory exchange ratio (R), defined as CO₂ elimination is divided by oxygen absorption, and remains steady between 0.8 and 0.9 in early to mid-exercise, with modest variance across people depending on their dietary fats and carbs balance. It’s worth noting that R is determined using exhaled gases, as opposed to cellular R, also known as the respiratory quotient (RQ), which is determined at the tissue level. R may rise transiently just before and during exercise as a result of anticipatory hyperventilation. Increases dramatically over the ventilatory threshold, and R rises above 1.0. When you stop exercising, your CO₂ levels drop quickly, but they stay high while your tissue CO₂ reserves are depleted. R can then rise to as high as 1.3 to 1.5 over the course of 1 to 2 minutes before dropping.

Characteristics of respiratory quotient

• In general, more oxidized compounds, such as glucose, require much less oxygen to be properly processed, and so have higher respiratory quotients. Conversely, compounds that are less oxidized, such as fatty acids, require more oxygen to complete their metabolism and so have lower respiratory quotients

• The caloric value of each litre (l) of carbon dioxide generated is referred to as the respiratory quotient. When data on oxygen consumption is available, it is typically utilised directly since it is a more direct and dependable measure of energy output

• The energy generated by protein is used to calculate the Respiratory Quotient. However, no one Respiratory Quotient can be allocated to the oxidation of protein in the diet due to the intricacy of the different methods in which distinct amino acids might be oxidized

• Insulin is assumed to be favorably related with an increase in the respiratory quotient, as it builds lipid stockpiling and diminishes fat oxidation. A higher respiratory remainder is the consequence of a positive energy balance

Applications

• The respiratory quotient has practical uses in severe cases of chronic obstructive pulmonary disease, when patients expend a lot of energy on respiratory effort. The respiratory quotient is pushed down by increasing the quantity of fats in the diet, resulting in a proportionate decrease in the amount of CO₂ generated. This minimises the amount of energy required on breathing by lowering the respiratory load to remove CO₂

• The Respiratory Quotient can be used to determine if a person is overfeeding or underfeeding. Underfeeding lowers the respiratory quotient by forcing the body to consume fat reserves, whereas overfeeding raises it by causing lipogenesis. A respiratory quotient of less than 0.85 implies underfeeding, whereas a respiratory quotient of more than 1.0 indicates overfeeding. This is especially essential in patients with limited respiratory systems, because a higher respiratory quotient correlates with higher respiratory rate and lower tidal volume, putting affected patients at danger

• The respiratory quotient is a tool that may be used to assess liver function and diagnose liver disease. Non-protein respiratory quotient (npRQ) values are effective indications in the prediction of overall survival rate in patients with liver cirrhosis. Patients with a npRQ of less than 0.85 had a worse survival rate than those with a npRQ of more than 0.85. A reduction in npRQ indicates that the liver is storing less glycogen.  As per past investigations, non-alcoholic greasy liver sickness is related with a low respiratory remainder esteem, and the non protein respiratory remainder esteem was a solid indicator of infection seriousness

• Aquatic scientists have recently employed the respiratory quotient to provide light on its environmental applications. RQ appears to be connected to the elemental makeup of the respired compounds, according to experiments with natural bacterioplankton utilising various single substrates. Bacterioplankton RQ is therefore proved to be not only a practical part of determining bacterioplankton respiration, but also an important ecosystem state variable that givesinteresting data about oceanic environment functioning. According to the stoichiometry of the many metabolised substrates, dissolved oxygen (O₂) and carbon dioxide (CO₂) in aquatic environments should covary inversely owing to  photosynthesis and respiration processing. We may learn more about metabolic activity and the combined roles of chemical and physical forces in shaping the biogeochemistry of aquatic ecosystems by using this quotient

Conclusion

The respiratory quotient (RQ) is the difference between the volume of carbon dioxide exhaled and the volume of oxygen received during breathing. When estimated from carbon dioxide generation to oxygen absorption, it is a dimensionless quantity employed in a computation for basal metabolic rate.