Can calculation of energy expenditure based on CO2 measurements replace indirect calorimetry?

Abstract

BackgroundMethods to calculate energy expenditure (EE) based on CO2 measurements (EEVCO2) have been proposed as a surrogate to indirect calorimetry. This study aimed at evaluating whether EEVCO2 could be considered as an alternative to EE measured by indirect calorimetry.MethodsIndirect calorimetry measurements conducted for clinical purposes on 278 mechanically ventilated ICU patients were retrospectively analyzed. EEVCO2 was calculated by a converted Weir’s equation using CO2 consumption (VCO2) measured by indirect calorimetry and assumed respiratory quotients (RQ): 0.85 (EEVCO2_0.85) and food quotient (FQ; EEVCO2_FQ). Mean calculated EEVCO2 and measured EE were compared by paired t test. Accuracy of EEVCO2 was evaluated according to the clinically relevant standard of 5% accuracy rate to the measured EE, and the more general standard of 10% accuracy rate. The effects of the timing of measurement (before or after the 7th ICU day) and energy provision rates (<90 or ≥90% of EE) on 5% accuracy rates were also analyzed (chi-square tests).ResultsMean biases for EEVCO2_0.85 and EEVCO2_FQ were -21 and -48 kcal/d (p = 0.04 and 0.00, respectively), and 10% accuracy rates were 77.7 and 77.3%, respectively. However, 5% accuracy rates were 46.0 and 46.4%, respectively. Accuracy rates were not affected by the timing of the measurement, or the energy provision rates at the time of measurements.ConclusionsCalculated EE based on CO2 measurement was not sufficiently accurate to consider the results as an alternative to measured EE by indirect calorimetry. Therefore, EE measured by indirect calorimetry remains as the gold standard to guide nutrition therapy.

The effect of cisatracurium infusion on the energy expenditure of critically ill patients: an observational cohort study

“…EEVCO 2 = 3.941 × VCO 2 (L/min) / respiratory quotient + 1.11 × VCO 2 (L/min) × 1440. The respiratory quotient was considered to be a fixed value of 0.86 [14][15][16]. The mechanical ventilator measured the VCO2 (Hamilton-S1, Hamilton Medical AG, Bonaduz, Switzerland), and every minute, data are automatically sent to our electronic patient data management system (MetaVision; iMDsoft MetaVision®, Tel Aviv, Israel).…”

Advances in Medical Nutrition Therapy: Parenteral Nutrition

“…Many mechanical ventilators can measure VCO2, which in turn can be used to calculate EE using Weir's formula by assuming the respiratory quotient (RQ). This method remains controversial; Rousing et al concluded that VCO2-based calorimetry is an accurate alternative to predictive equations with a 10% accuracy rate of 89% compared to IC [31], whereas Oshima et al found end-expiratory VCO2 (EEVCO2) to be insufficiently accurate, with a 10% accuracy rate of 77% compared to IC [32]. It is important to note that EEVCO2 requires the use of a constant estimated RQ value; most studies use an RQ value of 0.85.…”

Методичні Рекомендації ESPEN Щодо Клінічного Харчування У Відділенні Інтенсивної Терапії

“…×èñëåíí³ ìåòààíàë³çè ïîêàçàëè íèçüêå çíà÷åííÿ ïðîãíîñòè÷íèõ ð³âíÿíü [119,120], âàð³àáåëüí³ñòü ÿêèõ çá³ëüøóºòüñÿ, îñê³ëüêè ìàñà ò³ëà çàëèøàºòüñÿ çíà÷åííÿì, ÿêå âàaeêî òî÷íî îö³íèòè [121]. ßêùî íåïðÿìà êàëîðè-ìåòð³ÿ íåäîñòóïíà, òî ðîçðàõóíîê ÂÅÑ ç VCO 2 , îòðèìàíîãî ëèøå ç àïàðàòó øòó÷íî¿ âåíòèëÿö³¿ ëåãåí³â (ÂÅÑ = VCO 2 × 8,19), ïðîäåìîíñòðóâàâ á³ëüøó òî÷í³ñòü, í³ae ð³âíÿííÿ [122], àëå ìåíøó, í³ae ìåòîä íåïðÿìî¿ êàëîðèìåò𳿠[123]. Òàêîae ìîaeíà âèêîðèñòîâóâàòè VO 2 , âèðàõóâàíå ç êàòåòåðà ëåãåíåâî¿ àðòåð³¿.…”