Calculate the respiratory quotient (RQ) ratio from CO₂ production and O₂ consumption to determine metabolic substrate utilization and assess respiratory efficiency.
Respiratory Quotient (RQ)
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Predominant Substrate
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Metabolic Interpretation
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Respiratory quotient (RQ) is the ratio of CO₂ produced to O₂ consumed during metabolism. It indicates which type of fuel (carbohydrates, fats, or proteins) your body is primarily using for energy and helps assess metabolic efficiency.
RQ values typically range from 0.7 to 1.0. An RQ of 0.7 indicates fat oxidation, 0.85 indicates protein metabolism, and 1.0 indicates carbohydrate oxidation. Values above 1.0 may suggest anaerobic metabolism or hyperventilation.
These values are typically measured using indirect calorimetry equipment in clinical or research settings. The equipment analyzes expired air to determine gas exchange rates, usually expressed in mL/min or L/min.
RQ values can be influenced by diet composition, exercise intensity, metabolic state (fed vs fasted), disease conditions, and measurement timing. Physical activity and recent food intake significantly impact RQ measurements.
Normal resting RQ values typically range from 0.7 to 1.0, with an average around 0.8-0.85 for mixed substrate utilization. Values outside this range may indicate specific metabolic states or measurement errors.
Yes, RQ is used in indirect calorimetry to calculate energy expenditure more accurately. Different substrates require different amounts of oxygen and produce different amounts of CO₂ per calorie burned.
RQ values above 1.0 may indicate anaerobic metabolism, hyperventilation, or conversion of carbohydrates to fat (lipogenesis). In clinical settings, this could suggest respiratory distress or metabolic dysfunction.