What does the respiratory exchange ratio (RER) indicate?

• A. The rate of gas diffusion in the lungs
• B. Balance of carbon dioxide production and oxygen consumption
• C. The efficiency of pulmonary ventilation
• D. The volume of air in the alveoli

Answer: (B)

The respiratory exchange ratio (RER) is a significant measure that indicates the balance of carbon dioxide production and oxygen consumption in the body. It is calculated by measuring the volume of carbon dioxide produced (VCO2) relative to the volume of oxygen consumed (VO2) during respiration.

An RER value close to 0.7 typically suggests that fat is the predominant fuel being metabolized, while a value closer to 1.0 indicates that carbohydrates are the primary source of energy. This ratio provides insights into the metabolic state of an individual, informing us about their energy substrate utilization during rest or exercise. Understanding RER is crucial in fields such as exercise physiology, nutrition, and clinical assessments of respiratory and metabolic health.

The other options do not accurately characterize what RER signifies; for example, gas diffusion rate, pulmonary ventilation efficiency, or alveolar air volume pertain to different physiological concepts outside the specific context of RER.