Method And Applications For Indirect Calorimetry Based On The Ventilated Hood And Dilution Method

Malnutrition is a condition that results from imbalance of energy or nutrients and adversely affect human health. It includes under-nutrition and over-nutrition.Malnutrition and its resulting vital organ damage of inpatients and popularity of chronic disease have become a tremendous risk for hospitalized patients and important public health problem. It is an effective means to prevent malnutrition by clinical nutrition support and scientific guidance of exercise and dietary thought metabolic rate and substrates measurement. Indirect calorimetric ?IC? method has the advantages of relatively cheap and convenient among metabolic measurement methods. It has acted as an important method for nutrition assessment and nutrition support in clinical nutrition. However, the popularity of the IC is relatively low in China, especially for small and medium-sized hospitals and public health. There are some reasons contributed to this phenomenon: ?a? The equipment depends on the import, which causes the instrument to be expensive, and the cost of measurement and maintenance is high; ?b? The measurements are relatively time consuming and thus can not satisfy the high efficiency demand of hospital patients in China; ?c? The measurement requires professional operators. In view of the above situation, this dissertation conducts the following research:1. The establishment of an indirect calorimetry based on ventilated hood and dilution methodWe established an indirect calorimetry based on ventilated hood and dilution method through designing respiratory gas analysis method and building a test platform for gas collecting and analysis. The indirect calorimetry adopts the automatic control technology of electronic pressure, which used the feedback mechanism to control the pressure of the pipeline and to ensure accuracy of gas concentration measurement through adjustment of the proportional valve. We also adopted a steady state identification technology. It not only monitor and display state of the subjects' gas exchange parameters ?variation coefficient of VO₂ and VCO₂?, which may help operator master the status of subjects, but also can select the stable state interval data and then calculate measurement results, which may reduce operator dependencies.2. The study of reliability and validity of the newly developed indirect calorimetry Short-term repeated measurement experiments in 38 subjects were used to test the reliability. The intra-class correlation coefficient ?ICC?, variation coefficient ?CV%?and limits of agreement ?LoA? were acted as evaluation indexes. For the repeated measurements, we found that the ICC were 0.945 and 0.907, CV% were 5.9% and 8.3%,LoA were -21.0?29.land-27.7?30.9 for VO₂ and VCO₂, respectively. It indicated that the reliability achieved the level of the similar devices. Validation includes an in vitro simulation experiment and an in vivo experiment. ?a? In vitro: there were high correlation coefficient ?r=0.99,p<0.001 for both VO₂ and VCO₂? and narrow LoA ?VO₂:-1.14?6.48,VCO₂: -0.87?8.11? between simulated and measured values, ?b? In vivo:gas exchange variables were measured by our newly developed device and by V02000 in 38 subjects. There were high correlation coefficient ?VO₂: r=0.91, p<0.001,VCO₂:r=0.89,p<0.001?, small mean difference ?VO₂: 5.9%, VCO₂: 5.5%? and moderate LoA?VO₂: -26.9?50.3,VCO₂: -24.8?43.2?. These preliminary data indicated that it showed promise as an accurate and precise tool in the assessment of gas exchange variables.3. The study of fast access method of resting metabolic rateIn view of time consuming situation of current resting metabolic rate ?RMR?measurement method, this research focused on the fast access method of RMR. First,the feasibility of improvement the current RMR measurement protocol was studied. We proposed a sliding time window method ?1-min step size? to observe state profile of stability degree and metabolic rate. Then RMR measurements were conducted in 32 heathy adults. We found that it was feasible to optimize the current measurement protocol and shorten the measurement time. Second, we proposed a RMR acquisition method based on heart rate monitoring. The experimental results of 42 healthy adults showed that the method can obtained RMR accurately. The average time to obtained RMR was 14 minutes, which showed that the method can significantly reduce the measurement time. In addition, the method can personalized measurement time based on monitoring the state of subjects.4. The study of best prediction equations for Non-obese and healthy Chinese adultsThe prediction equations of RMR have the characteristics of no-cost and easy to use. It has important application values in the absence of IC. Researchers have found that the applicability of the RMR prediction equations varied among different populations. However, the study on the accuracy of the RMR prediction equations for non-obese adult population in China is still lacking. We assessed the accuracy of the 14 common used prediction equations by measured the RMR of 46 individuals. We found that all of the 14 prediction equations were not accurate enough. Thus, IC method is still the preferred method to evaluate RMR. Henry's equation is the most accurately,which is able to accurately estimate the RMR of about 70% of the population. It may be used as an alternative to IC in the absence of IC. Further research is needed to establish a RMR prediction equation for this specific populations based on large samples.