EE: Respiratory Quotient (RQ) in Healthy and Non-Critically Ill 2014
Click here to see the explanation of recommendation ratings (Strong, Fair, Weak, Consensus, Insufficient Evidence) and labels (Imperative or Conditional). To see more detail on the evidence from which the following recommendations were drawn, use the hyperlinks in the Supporting Evidence Section below.
EE: RQ Below 0.67 or Above 1.3 in Healthy Adults
If the respiratory quotient (RQ) falls outside the physiologic range (below 0.67 or above 1.3) in a healthy adult, the registered dietitian nutritionist (RDN) should suspect an error and repeat the resting metabolic rate (RMR) measurement. The physiologic range of RQ reflecting cellular metabolism across the fed and fasted state is 0.67 to 1.3.
EE: RQ Between 0.67 and 0.90 in Healthy Adults
If the RQ falls between 0.67 and 0.90 in a healthy adult, the RDN should accept the measurement because RQ values within this range cannot reliably be used to detect feeding protocol violations. RQ varies among healthy adults and the range of RQ between fed and fasted states overlaps. In individuals who fasted seven to 14 hours, research reports that RQ ranged from 0.68 to 0.90. Yet, in individuals who consumed a meal 2.5 hours prior to measurement, fasting RQ (0.79 to 0.81) increased by only 0.03 to 0.05. Research demonstrates that RQ has poor accuracy to evaluate feeding protocol violations.
EE: RQ Between 0.91 and 1.3 in Healthy Adults
If the RQ is between 0.91 and 1.3 in a healthy adult who has fasted, the RDN should suspect a problem and consider repeating the measurement. An RQ between 0.91 and 1.3 could be observed in an individual who has not fasted. However, it could also be due to an error in calibration, a leak in the calorimeter, a ventilation problem or some other artifact or protocol violation.
Risks/Harms of Implementing This Recommendation
There are no potential risks or harms associated with the application of these recommendations.
Conditions of Application
Clinical judgment should be used in applying these recommendations to healthy children and non-critically ill children and adults, due to no evidence in these populations.
Potential Costs Associated with Application
Increased cost may be incurred if the RMR measurement needs to be rescheduled due to a protocol violation.
EE: RQ Between 0.67 and 0.90 in Healthy Adults
- Eight studies provide evidence that in healthy adults who had fasted overnight (seven to 14 hours) per protocol prior to the RMR measurement, RQ ranged from 0.68 to 0.90. In addition, limited research regarding prolonged fasting (beyond 14 hours, violating protocol) reported that RQ declined with longer fasts to values as low as 0.65 after 22 hours of fasting. However, limited research reported that RQ remained below 1.0 even though subjects had eaten within the past 3.0 to 4.5 hours, violating protocol. In individuals who consumed a meal 2.5 hours prior to measurement, fasting RQ (0.79 to 0.81) increased by only 0.03 to 0.05. Research demonstrates that RQ is not sufficiently accurate to evaluate feeding protocol violations.
- Evidence is based on the following studies:
- Three neutral-quality randomized crossover trials (Johnston et al, 2002; Romijn et al, 1990; Weststrate and Hautvast, 1990)
- Two neutral-quality time series studies (Leff et al, 1987; Zauner et al, 1999)
- Two neutral-quality cross-sectional studies (Clark and Hoffer, 1991; Liu et al, 1995)
- One neutral-quality nonrandomized trial (Bissoli et al, 1999).
No studies were included in the evidence analysis of these recommendations. However, three review articles provide support for the recommendation.
- Sole metabolism of each macronutrient (i.e., carbohydrate, protein and fat) results in RQs of 1.0, 0.80 and 0.70; respectively. However, conditions such as hypoventilation or hyperventilation, under- or overfeeding, acid/base imbalance or ketone or ethanol metabolism could result in a physiological range for RQ of 0.67 to 1.3. Measurements outside the range of 0.67 to 1.0 are non-physiologic and should be considered an error due to inaccurate calibration, a leak in the calorimeter system or some other artifact (McClave et al, 2003; Feurer and McMullen, 1986; McClave and Snider, 1992).
Recommendation Strength Rationale
- The conclusion statement supporting EE: RQ Between 0.67 and 0.90 in Healthy Adults is grade II.
- The recommendations EE: RQ Below 0.67 or Above 1.3 in Healthy Adults and EE: RQ Between 0.91 and 1.3 in Healthy Adults are based on consensus.
- Risks/Harms of Implementing This Recommendation
The recommendations were created from the evidence analysis on the following questions. To see detail of the evidence analysis, click the blue hyperlinks below (recommendations rated consensus will not have supporting evidence linked).
Bissoli L, Armellini F, Zamboni M, Mandragona R, Ballarin A, Bosello O. Resting metabolic rate and thermogenic effect of food in vegetarian diets compared with Mediterranean diets. Ann Nutr Metab. 1999; 43: 140-144.
Clark HD, Hoffer LJ. Reappraisal of the resting metabolic rate of normal young men. Am J Clin Nutr. 1991; 53: 21-26.
Johnston CS, Day CS, Swan PD. Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy young women. J Am Coll Nutr. 2002; 21(1): 55-61.
Leff ML, Hill JO, Yates AA, Cotsonis GA, Heymsfield SB. Resting metabolic rate: Measurement reliability. Journal of Parenteral and Enteral Nutrition 1987; 11: 354-359.
Liu HY, Lu YF, Chen WJ. Predictive equations for basal metabolic rate in Chinese adults: A cross-validation study. J Am Diet Assoc. 1995; 95 (12): 1,403-1,408 and Liu HY, Lu YF, Chen WJ. Validity of predictive equations for the calculation of basal metabolic rate in healthy Chinese adults. Chinese Nutr Soc. 1994; 19 (2): 141-150.
Romijn JA, Godfried MH, Hommes MJ, Endert E, Sauerwein HP. Decreased glucose oxidation during short-term starvation. Metabolism. 1990 May; 39 (5): 525-530.
Weststrate JA, Hautvast JG. The effects of short-term carbohydrate overfeeding and prior exercise on resting metabolic rate and diet-induced thermogenesis. Metabolism. 1990; 39(12): 1,232-1,239.
Zauner C, Schneeweiss B, Kranz A, Madl C, Ratheiser K, Kramer L, Roth E, Schneider B, Lenz K. Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinehrine. Am J Clin Nutr. 1999;2000;71:1511-1515.
References not graded in Academy of Nutrition and Dietetics Evidence Analysis Process
- Feurer I, Mullen JL. Bedside measurement of resting energy expenditure and respiratory quotient via indirect calorimetry. Nutr Clin Prac. 1986; 1: 43-49.
- McClave SA, Snider HL. Use of indirect calorimetry in clinical nutrition. Nutr Clin Pract. 1992 Oct; 7 (5): 207-221. Review. PMID: 1289691.
- McClave SA, Lowen CC, Kleber MJ, McConnell JW, Jung LY, Goldsmith LJ. Clinical use of the respiratory quotient obtained from indirect calorimetery. J Parenter Enteral Nutr. 2003; 27 (1): 21-26.