ACCS Respiratory Practice Exam

Respiratory quotient reflects how efficiently cells extract energy by oxidizing substrates, and it is defined as the amount of carbon dioxide produced (VCO2) divided by the amount of oxygen consumed (VO2). This ratio shows what fuel is mainly being burned: carbohydrate oxidation pushes the value toward about 1.0, fat oxidation toward about 0.7, and protein around 0.8. That makes the correct statement the one that describes RQ as CO2 production per O2 consumed. The ratio is not inverted (VO2/VCO2), it does depend on which macronutrient is being metabolized, and the typical physiologic range is not 2.0–3.0 but roughly 0.7–1.0 (about 0.8 for a mixed diet).