Question

explain how RER is determined, what information it provides, and how this measure can be flawed in certain circumstances

Answer 1

RER - Respiratory exchange ratio is a ratio between amount of CO2 produced in metabolism and oxygen used

So the ratio is determined by comparing exhaled gas to room air.Ratio can be used for estimating Respiratory quotient

RER = VCO2 /VO2 ( for carbohydrates its value is 1 and for fats it is 0.7)

It provides information that which fuel ( carbohydrate or fat) is being metabolised to supply the body with energy.Its calculation is commonly in conjunction with exercises tests such as VO2 max test and can be used as indicator that participants are nearing exhaustion and limits of their cardio - respiratory system as RER greater than or equal to 1 is often used as secondary endpoint criterion of VO2 max test

This RER measure can be flawed in certain circumstances though RQ and RER terms to be synonyms but distinction is way in which each is measured as RER is measured using indirect calorimetry and Respiratory quotient can be measured across capillary bed of particular organ or even a collection of cell in vitro.

But during intensive exercises the value of RER vary from Respiratory quotient as RER can be higher than 1 in intense exercise by production of extra CO2 by bicarbonate buffering system during intense exercise causing change in values from Respiratory quotient , also during metabolic acidosis / alkalosis or Respiratory acidosis /alkalosis , thus it can be flawed in certain circumstances

Only during mild and moderate activities RER is equivalent as Respiratory quotient also in resting period which help in determining if difficulty weaning from mechanical ventilation or RQ of < 0.7 indicates or suggest underfeeding and use of ketone as fuel sources

PLEASE UPVOTE IF YOU FIND IT SATISFACTORY.COMMENT IF ANY DOUBT.