大島 拓

BACKGROUND & AIMS: The ICALIC project was initiated for developing an accurate, reliable and user friendly indirect calorimeter (IC) and aimed at evaluating its ease of use and the feasibility of the EE measurements in intensive care unit (ICU). METHODS: This was a prospective unblinded, observational, multi-center study. Simultaneous IC measurements in mechanically ventilated ICU patients were performed using the new IC (Q-NRG®) and currently used devices. Time required to obtain EE was recorded to evaluate the ease of use of Q-NRG® versus currently used ICs and EE measurements were compared. Conventional descriptive statistics were used: data as mean ± SD. RESULTS: Six centers out of nine completed the required number of patients for the primary analysis. Mean differences in the time needed by Q-NRG® against currently used ICs were -32.3 ± 2.5 min in Geneva (vs. Deltatrac®; p < 0.01), -32.3 ± 3.1 in Lausanne (vs. Quark RMR®; p < 0.05), -33.7 ± 1.4 in Brussels (vs. V-Max Encore®; p < 0.05), -26.4 ± 7.8 in Tel Aviv (vs. Deltatrac®; p < 0.05), -28.5 ± 3.5 in Vienna (vs. Deltatrac®; p < 0.05), and 0.3 ± 1.2 in Chiba (vs. E-COVX®; p = 0.17). EE (kcal/day) measurements by the Q-NRG® were similar to the Deltatrac® in Geneva and Vienna (mean differences±SD: -63.1 ± 157.8 (p = 0.462) and -22.9 ± 328.2 (=0.650)), but significantly different in Tel Aviv (307.4 ± 324.5, p < 0.001). Significant differences were observed in Lausanne (Quark RMR®: -224.4 ± 514.9, p = 0.038) and in Brussels (V-max®: -449.6 ± 667.4, p < 0.001), but none was found in Chiba (E-COVX®; 55.0 ± 204.1, p = 0.165). CONCLUSION: The Q-NRG® required a much shorter time than most other ICs to determine EE in mechanically ventilated ICU patients. The Q-NRG® is the only commercially available IC tested against mass spectrometry to ensure gas accuracy, while being very easy-to use.

RATIONALE: Accurate evaluation of the energy needs is required to optimize nutrition support of critically ill patients. Recent evaluations of indirect calorimeters revealed significant differences among the devices available on the market. A new indirect calorimeter (Q-NRG®, Cosmed, Roma, Italy) has been developed by a group of investigators supporting the international calorimetry study initiative (ICALIC) to achieve ultimate accuracy for measuring energy expenditure while being easy to use, and affordable. This study aims to validate the precision and the accuracy of the Q-NRG® in the in-vitro setting, within the clinically relevant range for adults on mechanical ventilation in the ICU. Mass spectrometry is the reference method for the gas composition analysis to evaluate the analytic performances of the Q-NRG®. METHODS: The accuracy and precision of the O2 and CO2 measurements by the Q-NRG were evaluated by comparing the measurements of known O2 and CO2 gas mixtures with the measurements by the mass spectrometer (Extrel, USA). The accuracy and precision of the Q-NRG® for measurements of VO2 (oxygen consumption) and VCO2 (CO2 production) at clinically relevant ranges (150, 250 and 400 ml/min STPD) were evaluated by measuring simulated gas exchange under mechanically ventilated setting at different FiO2 settings (21-80%), in comparison to the reference measurements by the mass spectrometer-based mixing chamber system. RESULTS: The measurements of gas mixtures of predefined O2 and CO2 concentrations by the Q-NRG® were within 2% accuracy versus the mass spectrometer measurements in Passing Bablok regression analysis. In a mechanically ventilated setting of FiO2 from 21 up to 70%, the Q-NRG® measurements of simulated VO2 and VCO2 were within 5% difference of the reference mass spectrometer measurements. CONCLUSION: In vitro evaluation confirms that the accuracy of the Q-NRG® indirect calorimeter is within 5% at oxygen enrichment to 70%; i.e. maximum expected for clinical use. Further recommendations for the clinical use of the Q-NRG® by will be released once the ongoing multi-center study is completed.

BACKGROUND & AIMS: This review aims to clarify the use of indirect calorimetry (IC) in nutritional therapy for critically ill and other patient populations. It features a comprehensive overview of the technical concepts, the practical application and current developments of IC. METHODS: Pubmed-referenced publications were analyzed to generate an overview about the basic knowledge of IC, to describe advantages and disadvantages of the current technology, to clarify technical issues and provide pragmatic solutions for clinical practice and metabolic research. The International Multicentric Study Group for Indirect Calorimetry (ICALIC) has generated this position paper. RESULTS: IC can be performed in in- and out-patients, including those in the intensive care unit, to measure energy expenditure (EE). Optimal nutritional therapy, defined as energy prescription based on measured EE by IC has been associated with better clinical outcome. Equations based on simple anthropometric measurements to predict EE are inaccurate when applied to individual patients. An ongoing international academic initiative to develop a new indirect calorimeter aims at providing innovative and affordable technical solutions for many of the current limitations of IC. CONCLUSION: Indirect calorimetry is a tool of paramount importance, necessary to optimize the nutrition therapy of patients with various pathologies and conditions. Recent technical developments allow broader use of IC for in- and out-patients.

BACKGROUND: Methods 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. METHODS: Indirect 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). RESULTS: Mean 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. CONCLUSIONS: Calculated 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.

BACKGROUND & AIMS: We hypothesize that an optimal and simultaneous provision of energy and protein is favorable to clinical outcome of the critically ill patients. METHODS: We conducted a review of the literature, obtained via electronic databases and focused on the metabolic alterations during critical illness, the estimation of energy and protein requirements, as well as the impact of their administration. RESULTS: Critically ill patients undergo severe metabolic stress during which time a great amount of energy and protein is utilized in a variety of reactions essential for survival. Energy provision for critically ill patients has drawn attention given its association with morbidity, survival and long-term recovery, but protein provision is not sufficiently taken into account as a critical component of nutrition support that influences clinical outcome. Measurement of energy expenditure is done by indirect calorimetry, but protein status cannot be measured with a bedside technology at present. CONCLUSIONS: Recent studies suggest the importance of optimal and combined provision of energy and protein to optimize clinical outcome. Clinical randomized controlled studies measuring energy and protein targets should confirm this hypothesis and therefore establish energy and protein as a power couple.