Day‐to‐day variation in oxygen consumption at submaximal loads during ergometer cycling by adolescents

The day‐to‐day variation in oxygen consumption (V˙O₂) during ergometer cycling by 20 healthy adolescents, 10 females and 10 males, was measured using indirect calorimetry. The two sets of measurements were performed on two consecutive days. Great care was taken to minimize possible disturbing factors. Cycling started at 50 and 100 W for female and male adolescents, respectively. The load was increased at a rate of 5 W 30 s^?1. In order to reach steady state, the load was kept constant for 3·5 min twice during the cycling session, at 100 and 130 W for the females and at 130 and 160 W for the males. Cycling continued until exhaustion. The maximal loads were 196 W (mean) and 271 W (mean) for females and males, respectively. At the maximal loads the day‐to‐day variation (±2 SD) in oxygen consumption (V˙O₂) was ±330 ml min^?1 for females and 390 ml min^?1 for males. At the submaximal loads the day‐to‐day variation in heart rate (HR) was 9·3 beats min^?1 (±2 SD) (coefficient of variation, CV=3·4% at 130 W) for both sexes. The day‐to‐day variation in oxygen consumption (V˙O₂) was ±199 ml min^?1 (±2 SD) at the different submaximal loads and did not differ between female and male adolescents (CV=5·7% at 130 W). This natural day‐to‐day variation must be taken into consideration when using a submaximal ergometer cycling test for the evaluation of physical capacity in the two sexes.     

Resting energy expenditure and nutritional status in patients undergoing transthoracic esophagectomy for esophageal cancer

This study was to assess the resting energy expenditure of patients with esophageal cancer using indirect calorimetry. Eight male patients with esophageal cancer and eight male healthy controls were enrolled in this study. All patients underwent transthoracic esophagectomy with lymph nodes dissections. The resting energy expenditure was measured preoperatively, and on postoperative day 7 and 14 using indirect calorimetry. Preoperatively, the measured resting energy expenditure/body weight in these patients was significantly higher than that of the controls (23.3 ± 2.1 kcal/kg/day vs 20.4 ± 1.6 kcal/kg/day), whereas the measured/predicted energy expenditure from the Harris-Benedict equation ratio was 1.01 ± 0.09, which did not differ significantly from the control values. The measured resting energy expenditure/body weight was 27.3 ± 3.5 kcal/kg/day on postoperative day 7, and 23.7 ± 5.07 kcal/kg/day on postoperative day 14. Significant increases in the measured resting energy expenditure were observed on postoperative day 7, and the measured/predicted energy expenditure ratio was 1.17 ± 0.15. In conclusion, patients with operable esophageal cancers were almost normometabolic before surgery. On the other hand, the patients showed a hyper-metabolic status after esophagectomy. We recommended that nutritional management based on 33 kcal/body weight/day (calculated by the measured resting energy expenditure × active factor 1.2–1.3) may be optimal for patients undergoing esophagectomy.     

Comparison of resting energy expenditure measurements by ventilated canopy and by respiration chamber

The study compared measurements of resting energy expenditure (REE) by two methods, namely the commercially available ventilated canopy (Medgraphics CCM system) and the respiration chamber. Thirty-five healthy subjects of both sexes with a wide weight range (BMI 18–33·8 kg m^?2) were measured on both systems. The linear regression equation was REE_canopy=0·66 × REE_resp.cham. + 61·1 (kJ h^?1), and the corresponding SEE% was 8·6%. The correlation was high (r=0·89). However, the mean REE measured using the ventilated canopy was 41 kJ h^?1 (13%) lower than that using the respiration chamber (P<0·01). The Medgraphics CCM canopy system seems valid for measurements of REE. However, the REE results measured by the canopy were systematically lower than when measured by the respiration chamber, but can be converted by the equation given with an accuracy error of 9%.     

Resting energy expenditure in patients undergoing pylorus preserving pancreatoduodenectomies for bile duct cancer or pancreatic tumors

We measured the energy expenditure weekly in patients undergoing a pylorus preserving pancreatoduodenectomy for bile duct cancer or pancreatic tumors. Twelve patients (5 women and 7 men; mean age 70.1 years) were enrolled in this study, and their resting energy expenditure levels were determined by indirect calorimetry. In these patients, a significant correlation was observed between the measured resting energy expenditures and the predicted resting energy expenditures calculated by the Harris-Benedict equation. The resting energy expenditures measured before surgery were almost the same as the predicted resting energy expenditures (measured resting energy expenditure: 22.4 ± 3.9 kcal/kg/day vs predicted resting energy expenditure: 21.7 ± 2.0 kcal/kg/day). The measured resting energy expenditure/predicted resting energy expenditure ratio, which reflects the stress factor, was 1.02 ± 0.10. After the pylorus preserving pancreatoduodenectomy, a significant increase in energy expenditure was observed, and the measured resting energy expenditure was 25.7 ± 3.5 kcal/kg/day on postoperative day 7 and 25.4 ± 4.9 kcal/kg/day on postoperative day 14. The measured resting energy expenditure/predicted resting energy expenditure ratio was 1.16 ± 0.14 on postoperative day 7, and 1.16 ± 0.18 on postoperative day 14 respectively. In conclusion, patients undergoing a pylorus preserving pancreatoduodenectomy showed a hyper-metabolic status as evaluated by their measured resting energy expenditure/predicted resting energy expenditure ratio. From our observations, we recommend that nutritional management based on 30 kcal/body weight/day (calculated by the measured resting energy expenditure×activity factor 1.2–1.3) may be optimal for patients undergoing a pylorus preserving pancreatoduodenectomy.     

间接测热法与传统能量估算法测定重症监护病房患者能量消耗的比较

目的 比较间接测热法测定能量消耗值(MEE)与传统方法得到估计能量消耗值(EEE)的差异,为危重患者的能量补充提供依据.方法 采用自身前后对照研究方法,对57例重症监护病房(ICU)患者使用间接测热法得到MEE,使用传统能量估算法如HB公式法、HB系数法和体重法得到EEE,其中低体重者[体质指数(BMI)<18.4 kg/m2]使用理想体重表计算,并以EEE与MEE的比值来评价估算能量的准确性.结果 HB公式法、HB系数法和实际体重法得到的EEE与间接测热法得到MEE比较差异均有统计学意义[(6335±1004)kJ、(9125±1795)kJ、(7188±1029)kJ比(7753±1439)kJ,P<0.05或P<0.01].HB系数法与实际体重法比较差异也有统计学意义(P<0.01),且后者的结果更接近实际测定值.用HB公式法估计能量会造成多数患者营养不足[低体重者占100%(4/4);体重正常者(BMI 18.5～23.9 kg/m2)占73.59%(39/53)].低体重者使用理想体重估算能量均能在营养充足范围内[100%(4/4)];体重正常者使用HB系数法和实际体重法可造成大量的营养不足[分别占39.62%(21/53)和43.39%(23/53)]及营养过度(分别占24.53%(13/53)和13.22%(7/53)].结论 对于危重病患者,各种传统公式估算能量消耗都很不精确,容易造成大量的营养不足和营养过度,最好使用间接测热法测定目标能量;在没有间接能量测定仪的情况下,低体重者使用理想体重,而体重正常者使用实际体重的估算法似乎较为合理.

Abstract：

Objective To compare measurement of energy expenditure(MEE)by indirect calorimetry (IC)with traditional estimation of energy expenditure(EEE),to provide a basis for energy supplementary for critically ill patients.Methods Using self-controlled study,the energy expenditure of 57 intensive care nnit(ICU)patients was measured by IC.Meanwhile,EEE was also calculated using the following equations:Harris-Benedict(HB),HB×factor,or 104.6 kJ/kg.Body weight were calculated using actual body weight(ABW)or ideal body weight(IBW).If body mass index(BMI)<18.4 kg/m2 it was considered as underweight,and the IBW was selected from the IBW table.The potential adequacy of estimated energy was assayed by ratio of EEE/MEE.Results There was significant difference in MEE by IC and EEE by HB,HB×factor and 104.6 kJ/kg [(6335±1004)kJ,(9125±1795)kJ,(7188±1029)kJ vs.(7753±1439)kJ,P<0.05 or P<0.01].There was significant difference between EEE by HB × factor and 104.6 kJ/kg(P<0.01),and EEE by 104.6 kJ/kg×ABW,and the latter was closer to MEE.Underfeeding would occur in most ICU patients if HB equation was used [100%(4/4)in underweight patients and 73.59%(39/53)in normal weight(BMI 18.5-23.9 kg/m2)].EEE as calculated by 104.6 kJ/kg ×IBW was reasonable in the underweight patients 100%(4/4),but EEE in the patients with normal weight by using HB×factor or 104.6 kJ/kg × ABW resulted in significant underfeeding[39.62%(21/53)and 43.39%(23/53)]or overfeeding[24.53%(13/53)and 13.22%(7/53)].Conclusion EEE derived from the equations was extremely inaccurate and may result in significant underfeeding or overfeeding in individuals.On the basis of this study we would recommend IC for measuring energy expenditure in ICU patients.Otherwise,the equations of 104.6 kJ/kg × IBW in underweight and 104.6 kJ/kg × ABW in normal weight patients may be reasonable.     

Evaluation of a mobile unit for indirect calorimetry during spontaneous ventilation

Summary The Mijnhardt Oxycon-4 (OX-4), designed for measurements of gas exchange during exercise using a mouth-piece, was adapted for use in recumbant patients by the introduction of a transparent canopy and a suction device. This system was evaluated in laboratory models and in patients.     

Relationship between oxygen cost of walking and level of walking disability after stroke: An experimental study

Background and Purpose

Since physical inactivity is the major risk factor for recurrent stroke, it is important to understand how level of disability impacts oxygen uptake by people after stroke. This study investigated the nature of the relationship between level of disability and oxygen cost in people with chronic stroke.

Methods

Level of walking disability was measured as comfortable walking speed using the 10‐m Walk Test reported in m/s with 55 ambulatory people 2 years after stroke. Oxygen cost was measured during 3 walking tasks: overground walking at comfortable speed, overground walking at fast speed, and stair walking at comfortable speed. Oxygen cost was calculated from oxygen uptake divided by distance covered during walking and reported in ml?kg^?1?m^?1.

Results

The relationship between level of walking disability and oxygen cost was curvilinear for all 3 walking tasks. One quadratic model accounted for 81% (95% CI [74, 88]) of the variance in oxygen cost during the 3 walking tasks:

Discussion

The oxygen cost of walking was related the level of walking disability in people with chronic stroke, such that the more disabled the individual, the higher the oxygen cost of walking; with oxygen cost rising sharply as disability became severe. An equation that relates oxygen cost during different walking tasks according to the level of walking disability allows clinicians to determine oxygen cost indirectly without the difficulty of measuring oxygen uptake directly.     

脓毒性休克时大鼠全身氧供给与氧消耗关系的变化

目的：观察脓毒性休克时全身氧供给（ＤＯ２）与氧消耗（ＶＯ２）关系的变化。方法：以改良的盲肠结扎穿孔（ＣＬＰ）方法制备大鼠脓毒性休克模型，观察大鼠休克过程中ＤＯ２、ＶＯ２、氧摄取率（ＥＲＯ２）等变化。结果：ＣＬＰ后５小时已出现平均动脉压明显下降（Ｐ＜０．０５）。在休克早期，ＤＯ２即进行性下降，ＥＲＯ２出现代偿性升高，ＶＯ２维持相对不变，呈非氧供依赖关系；当ＤＯ２降至３４．６０ｍｌ·ｋｇ－１／ｍｉｎ后，ＶＯ２随ＤＯ２线性降低（ｒ＝０．７３３，Ｐ＜０．０１），即呈病理性氧供依赖关系。结论：脓毒性休克时ＤＯ２与ＶＯ２间呈双相变化关系，病理性氧供依赖的出现与组织氧摄取和氧利用功能障碍有关。     

Sequence effects of combined resistance exercises with step choreography in the same session in women's oxygen uptake during and postexercise

The combination of step choreography (SC) with resistance training exercises (RE) in the same session is common in class fitness rooms populated mainly by women to increase energy expenditure. The aim of this study was to evaluate the differences in the exercise oxygen uptake and postexercise between two different combinations of resistance training exercises and step choreography, regarding the order of execution. Thirteen active women (30·31 ± 4·42 years, 62·02 ± 5·37 kg, 162·65 ± 4·40 cm, 19·14 ± 3·29% body fat) performed two combinations: step choreography before resistance training, where resistance training was divided into two blocks of analysis (10 min each); and step choreography divided into three equal blocks (10 min for each block), before, in the middle and after resistance exercise. There were significant differences (P<0·05) between the two sessions in oxygen uptake postexercise in the period of 0–5 min. A significant increase (P<0·0001) in the oxygen uptake absolute and relative in the heart rate between blocks 1 and 2 of resistance exercise in the two sessions was observed. In the step choreography in blocks, a significant (P = 0·001) decrease between blocks 2 and 3 in the step choreography before resistance exercise and a significant (P<0·05) increase in the heart rate in both sessions between blocks were observed. The combination of step choreography and resistance exercises during the same exercise session is a good strategy to promote an elevation of women's oxygen uptake during and after an exercise session, independent of the sequence used.     

Validity of wearable actimeter computation of total energy expenditure during walking in post-stroke individuals

BackgroundRecent studies reported that wearable sensor devices show low validity for assessing the amount of energy expenditure in individuals after stroke.ObjectiveWe aimed to evaluate the validity of energy expenditure calculation based on the product of energy cost and walked distance estimated by wearable devices in individuals after hemispheric stroke.MethodsWe recruited individuals with hemispheric stroke sequelae who were able to walk without human assistance. The participants wore a tri-axial accelerometer (Actigraph GT3x) and a pedometer (ONStep 400) on the unaffected hip in addition to a respiratory gas exchange analyzer (METAMAX 3B) during 6 min of walking at their self-selected walking speed and mode. The energy expenditure was calculated from the product of energy cost measured by the METAMAX 3B and the distance estimated by wearable devices. It was compared to the energy expenditure measured by the METAMAX 3B and the energy expenditure values recorded by the devices according to the manufacturer's algorithms. The validity was investigated by Bland-Altman analysis (mean bias [MB], root mean square error [RMSE], limits of agreement [95%LoA]), and Pearson correlation analysis (r).ResultsWe included 26 participants (mean [SD] age 64.6 [14.8] years). With the pedometer, the energy expenditure calculated from the product of energy cost and walked distance showed high accuracy and agreement with METAMAX 3B values (MB = −1.6 kcal; RMSE = 4.1 kcal; 95%LoA = −9.9; 6.6 kcal; r = 0.87, P < 0.01) but low accuracy and agreement with Actigraph GT3x values (MB = 15.7 kcal; RMSE = 8.7 kcal; 95%LoA = −1.3; 32.6 kcal; r = 0.44, P = 0.02) because of poorer estimation of walked distance. With the pedometer, this new method of calculation strongly increased the validity parameter values for estimating energy expenditure as compared with the manufacturer's algorithm.ConclusionsThis new method based on the energy cost and distance estimated by wearable devices provided better energy expenditure estimates for the pedometer than did the manufacturer's algorithm. The validity of this method depended on the accuracy of the sensor to measure the distance walked by an individual after stroke.     

Changes in energy metabolism after induction therapy in patients with severe or moderate ulcerative colitis

We investigated the changes in energy expenditure during induction therapy in patients with severe or moderate ulcerative colitis. Thirteen patients (10 men, 3 women; mean age, 36.5 years) with ulcerative colitis admitted to the Shiga University Hospital were enrolled in this study. We measured the resting energy expenditure and respiratory quotients of these patients before and after induction therapy with indirect calorimetry. We analyzed the changes of nutritional status and serum inflammatory cytokine levels and also evaluated the relationship between energy metabolism and disease activity by using the Seo index and Lichtiger index. The resting energy expenditure was 26.3 ± 3.8 kcal/kg/day in the active stage and significantly decreased to 23.5 ± 2.4 kcal/kg/day after induction therapy (p<0.01). The resting energy expenditure changed in parallel with the disease activity index and C-reactive protein and inflammatory cytokine levels. The respiratory quotient significantly increased after induction therapy. Thus, moderate to severe ulcerative colitis patients had a hyper-metabolic status, and the energy metabolism of these patients significantly changed after induction therapy. Therefore, we recommend that nutritional management with 30–34 kcal/kg/day (calculated as measured resting energy expenditure × activity factor, 1.3) may be optimal for hospitalized ulcerative colitis patients.     

Differences in energy expenditure during high-speed versus standard-speed yoga: A randomized sequence crossover trial

ObjectivesTo compare energy expenditure and volume of oxygen consumption and carbon dioxide production during a high-speed yoga and a standard-speed yoga program.DesignRandomized repeated measures controlled trial.SettingA laboratory of neuromuscular research and active aging.InterventionsSun-Salutation B was performed, for eight minutes, at a high speed versus and a standard-speed separately while oxygen consumption was recorded. Caloric expenditure was calculated using volume of oxygen consumption and carbon dioxide production.Main outcome measuresDifference in energy expenditure (kcal) of HSY and SSY.ResultsSignificant differences were observed in energy expenditure between yoga speeds with high-speed yoga producing significantly higher energy expenditure than standard-speed yoga (MD = 18.55, SE = 1.86, p < 0.01). Significant differences were also seen between high-speed and standard-speed yoga for volume of oxygen consumed and carbon dioxide produced.ConclusionsHigh-speed yoga results in a significantly greater caloric expenditure than standard-speed yoga. High-speed yoga may be an effective alternative program for those targeting cardiometabolic markers.     

Oxygen consumption and mixed venous oxygen saturation monitoring during orthotopic liver transplantation

Mixed venous oxygen saturation monitoring has been advocated for some critically ill patients. Patients with end-stage hepatic failure have oxygen consumption rates that are lower than normal. Using the Fick equation, oxygen consumption may be calculated if mixed venous and arterial oxygen tensions (and saturations), hemoglobin, and cardiac output are determined simultaneously. This report describes a unique pattern of changes in and oxygen consumption in 7 patients undergoing liver transplantation. A previous study correlated plasma carbohydrate (glucose) levels with early hepatic graft survival. After induction, the 7 patients reported here had low oxygen consumption and high values. The oxygen consumption rates decreased to the lowest point during the anhepatic phase and rose above baseline by the end of the case. The and oxygen consumption data reported here follow the presence of presumed hepatic metabolic activity (increased CO₂ and ionized calcium). Further research must be completed to determine whether these measurements indicate early hepatic nonfunction.     

Oxygen consumption and mixed venous oxygen saturation monitoring during orthotopic liver transplantation

Mixed venous oxygen saturation monitoring has been advocated for some critically ill patients. Patients with end-stage hepatic failure have oxygen consumption rates that are lower than normal. Using the Fick equation, oxygen consumption may be calculated if mixed venous and arterial oxygen tensions (and saturations), hemoglobin, and cardiac output are determined simultaneously. This report describes a unique pattern of changes in and oxygen consumption in 7 patients undergoing liver transplantation. A previous study correlated plasma carbohydrate (glucose) levels with early hepatic graft survival. After induction, the 7 patients reported here had low oxygen consumption and high values. The oxygen consumption rates decreased to the lowest point during the anhepatic phase and rose above baseline by the end of the case. The and oxygen consumption data reported here follow the presence of presumed hepatic metabolic activity (increased CO₂ and ionized calcium). Further research must be completed to determine whether these measurements indicate early hepatic nonfunction.     

Comparison of measured and predicted energy expenditure in mechanically ventilated children

Objective: To determine the energy requirements in mechanically ventilated pediatric patients using indirect calorimetry and to compare the results with the predicted metabolic rate. Design: In 50 mechanically ventilated children with a moderate severity of illness, energy expenditure was measured by indirect calorimetry. Daily caloric intake was recorded for all patients. Total urinary nitrogen excretion was determined in 31 patients. Results: Although there was a close correlation between the measured total energy expenditure (mTEE) and the predicted basal metabolic rate (pBMR) (r = 0.93, p < 0.001), Bland–Altman analysis showed lack of agreement between individual mTEE and pBMR values. The ratio of caloric intake/mTEE was significantly higher in the patients with a positive nitrogen balance (1.4 ± 0.07) compared with those with a negative nitrogen balance (0.8 ± 0.1; p < 0.001). Conclusions: Standard prediction equations are not appropriate to calculate the energy needs of critically ill, mechanically ventilated children. Individual measurements of energy expenditure and respiratory quotient by means of indirect calorimetry in combination with nitrogen balance are necessary for matching adequate nutritional support. Received: 27 June 1997 Accepted: 12 February 1998     

Changes in energy expenditure and fat metabolism in rats infused with interleukin-1

Metabolic alterations related to resting energy expenditure (REE) and fat metabolism have been noted during sepsis, and often depend on the causative agent and the stage and severity of the illness. We studied the effect of IL-1, the protein mediator of the 'acute phase' response during infection, on REE, respiratory quotient (RQ), and fat metabolism in male rats (210 g), who were infused over an 8-h period with (1-14C)-palmitate (PALM), (2-3H)-glycerol (GLY) and either saline or interleukin-1 (IL-1). At 7-8 h post infusion, the IL-1 group showed a significant increase in REE but no change in RQ. The IL-1 group also exhibited a significant decrease in serum free fatty acid (FFA) and an increase in FFA clearance. Free fatty acid flux, %PALM oxidation, serum (GLY), glycerol clearance, and glycerol flux (a measure of lipolytic rate) were not significantly different between the two groups. We conclude that IL-1 can mimic the increase in REE seen during infection; the increase in REE is not due to a selective increase in fat oxidation only, although the unchanged RQ and increased REE suggest that there is a proportional increase in net FFA oxidation.     

Meal-induced thermogenesis in obese patients before and after weight reduction

Summary. The purpose of this study was to find out whether human obesity is associated with a diminished meal-induced thermogenesis and, if so, to what extent this response is influenced by weight reduction. Ten obese subjects (body mass index 42 ± 2) and 10 age- and sex-matched non-obese volunteers were studied with continuous indirect calorimetry in the basal state and after the ingestion of a standardized test meal. Six obese subjects (body mass index 44 ± 2) were examined on two occasions, once before and once after gastric banding and an average weight reduction of 18 ± 3 kg. Basal oxygen uptake and energy expenditure were 30% (P<0·001) greater in the obese subjects compared to non-obese controls. After the meal, pulmonary oxygen uptake and energy expenditure increased rapidly and reached a relatively constant level after 60 min; for pulmonary oxygen uptake the average rise above basal was less in the obese (17·7 ± 1·6%) than the non-obese (27·8 ± 1·9%, P<0·001); the increase in energy expenditure was 18·5 ± 1·7% in obese and 30·8 ± 2·1% in non-obese subjects (P<0·001). After weight reduction, oxygen uptake and energy expenditure in the basal state were 20% lower (P<0·05) than before weight reduction. The average postprandial increase in oxygen uptake was greater after weight reduction (24·8 ± 2·0%) than before (16·7 ± 1·6%, P<0·001). Corresponding values for energy expenditure were 27·2 ± 2·2 and 18·2 ± 2·2% (P<0·001). It is concluded that: (1) the thermogenic response to a mixed meal is lower in obese compared to non-obese individuals; and, (2) this impaired response is partly normalized after weight reduction. These findings suggest that a diminished meal-induced thermogenesis is a secondary phenomenon rather than a primary pathogenic factor in human obesity.     

Influence of insulin on glucose metabolism and energy expenditure in septic patients

Introduction  

It is recognized that administration of insulin with glucose decreases catabolic response in sepsis. The aim of the present study was to compare the effects of two levels of insulinaemia on glucose metabolism and energy expenditure in septic patients and volunteers.     

重症感染患者应激激素和细胞因子与能量消耗的关系

目的：确立能反映能量代谢应激程度的有效指标,为营养支持时的能量补充量提供参考依据。方法：同步测定重症感染患者静息能量消耗（ＲＥＥ）、应激激素、细胞因子〔包括肿瘤坏死因子（ＴＮＦ）、白介素 ６（ＩＬ６）〕水平,并作疾病严重度评分（ＡＰＡＣＨＥⅡ）和感染严重度评分（ＳＳＳ）。将患者分为高代谢（ＲＥＥ／ＨＢ≥１１０％ ）及正常代谢（ＲＥＥ／ＨＢ＜ １１０％ ）２组,分析各指标与能量消耗变化的相关程度。结果：虽然感染组患者的ＴＮＦ、ＩＬ ６、糖皮质激素和Ｃ 反应蛋白（ＣＲＰ）水平及ＡＰＡＣＨＥⅡ、ＳＳＳ评分均明显高于对照组（Ｐ均＜ ０．０５）,但只有ＩＬ ６、糖皮质激素和ＣＲＰ与能量消耗间存在密切关系（Ｐ＜ ０．０５）。结论：疾病种类及严重度评分不能判断患者是否存在能量代谢的应激,ＣＲＰ、ＩＬ ６ 和糖皮质激素是预测感染患者能量消耗变化的有效指标