Légcserearány

Légcserearány, often translated as gas exchange ratio or respiratory quotient (RQ), is a dimensionless quantity in physiology and biochemistry that represents the ratio of carbon dioxide produced by metabolic processes to the amount of oxygen consumed. This ratio is typically expressed as CO2/O2. The value of the légcserearány varies depending on the type of fuel being metabolized by an organism.

For example, when carbohydrates are the primary energy source, the légcserearány is close to 1.0 because the complete oxidation of glucose (C6H12O6 + 6O2 → 6CO2 + 6H2O) produces an equal molar amount of carbon dioxide and consumes oxygen. For fats, the légcserearány is generally lower, around 0.7, due to their more complex chemical structure which requires more oxygen for complete breakdown. Proteins have an intermediate légcserearány, typically around 0.8.

In clinical settings, particularly in intensive care, monitoring the légcserearány can provide insights into a patient's metabolic state and the effectiveness of nutritional support. It can help determine whether a patient is being overfed or underfed and can indicate the proportion of different macronutrients being utilized for energy. Deviations from expected values can also suggest underlying metabolic abnormalities or imbalances. While a useful indicator, the légcserearány is just one piece of the puzzle in assessing a patient's overall metabolic health.