Henrik Rasmussen

Nutritional risk screening (NRS 2002): a new method based on an analysis of controlled clinical trials

BACKGROUND & AIMS A system for screening of nutritional risk is described. It is based on the concept that nutritional support is indicated in patients who are severely ill with increased nutritional requirements, or who are severely undernourished, or who have certain degrees of severity of disease in combination with certain degrees of undernutrition. Degrees of severity of disease and undernutrition were defined as absent, mild, moderate or severe from data sets in a selected number of randomized controlled trials (RCTs) and converted to a numeric score. After completion, the screening system was validated against all published RCTs known to us of nutritional support vs spontaneous intake to investigate whether the screening system could distinguish between trials with a positive outcome and trials with no effect on outcome. METHODS The total number of randomized trials identified was 128. In each trial, the group of patients was classified with respect to nutritional status and severity of disease, and it was determined whether the effect of nutritional intervention on clinical outcome was positive or absent. RESULTS Among 75 studies of patients classified as being nutritionally at-risk, 43 showed a positive effect of nutritional support on clinical outcome. Among 53 studies of patients not considered to be nutritionally at-risk, 14 showed a positive effect (P=0.0006). This corresponded to a likelihood ratio (true positive/false positive) of 1.7 (95% CI: 2.3-1.2). For 71 studies of parenteral nutrition, the likelihood ratio was 1.4 (1.9-1.0), and for 56 studies of enteral or oral nutrition the likelihood ratio was 2.9 (5.9-1.4). CONCLUSION The screening system appears to be able to distinguish between trials with a positive effect vs no effect, and it can therefore probably also identify patients who are likely to benefit from nutritional support.

Increase in incidence and prevalence of inflammatory bowel disease in northern Denmark: A population-based study, 1978-2002

Objectives Although incidence rates of inflammatory bowel disease have been reported worldwide, few long-term population-based studies with current time-trend analyses exist. We therefore examined time trends in the incidence rate of inflammatory bowel disease in a 25-year study period, and estimated the prevalence in 2002. All patients diagnosed between 1978 and 2002 were included as incident cases (n=2326) and all patients living in North Jutland County on 31 December 2002 were used to estimate prevalent cases (n=2205). Methods Medical records of all patients diagnosed with ulcerative colitis and Crohns disease in the North Jutland County Hospital Discharge Registry were reviewed to examine if the diagnostic criteria were fulfilled. Age-specific and gender-specific standardized incidence rates were calculated. Results For ulcerative colitis, incidence rates in women increased from 8.3 (95% confidence interval (CI): 6.7–9.9) in 1978–1982 to 17.0 (95% CI: 14.7–19.3) per 100 000 person-years in 1998–2002. The corresponding figures for men were 7.7 (95% CI: 6.1–9.3) and 16.7 (95% CI: 14.4–18.8) per 100 000 person-years. For Crohns disease, the incidence rates in women increased from 4.1 (95% CI: 3.0–5.2) in 1978–1982 to 10.7 (95% CI: 8.8–12.5) per 100 000 person-years in 1998–2002. The corresponding figures for men were 3.2 (95% CI: 2.1–4.2) and 8.5 (95% CI: 6.9–10.2) per 100 000 person-years. The prevalence of ulcerative colitis and Crohns disease was 294 and 151 per 100 000 inhabitants, respectively. Conclusions A marked and parallel increase was seen in both ulcerative colitis and Crohns disease in both genders during the last 25 years, with a corresponding high prevalence of both diseases.

Measuring nutritional risk in hospitals

About 20%–50% of patients in hospitals are undernourished. The number varies depending on the screening tool amended and clinical setting. A large number of these patients are undernourished when admitted to the hospital, and in most of these patients, undernutrition develops further during hospital stay. The nutrition course of the patient starts by nutritional screening and is linked to the prescription of a nutrition plan and monitoring. The purpose of nutritional screening is to predict the probability of a better or worse outcome due to nutritional factors and whether nutritional treatment is likely to influence this. Most screening tools address four basic questions: recent weight loss, recent food intake, current body mass index, and disease severity. Some screening tools, moreover, include other measurements for predicting the risk of malnutrition. The usefulness of screening methods recommended is based on the aspects of predictive validity, content validity, reliability, and practicability. Various tools are recommended depending on the setting, ie, in the community, in the hospital, and among elderly in institutions. The Nutrition Risk Screening (NRS) 2002 seems to be the best validated screening tool, in terms of predictive validity ie, the clinical outcome improves when patients identified to be at risk are treated. For adult patients in hospital, thus, the NRS 2002 is recommended.

Measurement of gastrointestinal pH and regional transit times in normal children

Summary: Gastrointestinal pH and regional intestinal transit times of a capsule were measured in twelve healthy children aged 8–14 years using a radiotransmitting pH-sensitive capsule. The location of the capsule was determined by fluoroscopy. pH in the stomach was 1.5, but rose to 6.4 in the duodenum (mean values). pH gradually rose in the small intestine and reached an alkaline peak value of 7.4 in the distal part. pH dropped to 5.9 in the cecum but rose to 6.5 in the rectum. Median gastric residence time of the capsule was 1.1 h. Small intestinal transit time was 7.5 h, and colonic transit time was 17.2 h. pH profile and intestinal transit times found in the present study are almost identical to values found in studies on healthy adults. It is therefore concluded that the release pattern of pH-dependent sustained-release tablets in children is likely to be equal to that of adults.

Nonlinear superheat and capacity control of a refrigeration plant

This paper proposes a novel method for superheat and capacity control of refrigeration systems. The main idea is to control the superheat by the compressor speed and capacity by the refrigerant flow. A new low order nonlinear model of the evaporator is developed and used in the design of the nonlinear controller. The proposed method is validated by experimental results.

Sensorless field oriented control of a PM motor including zero speed

This paper presents a simple control method for controlling permanent magnet synchronous motors (PMSM) in a wide speed range without a shaft sensor. The method estimates the stator flux by integration of the measured BEMF signal. To compensate for the offset in the BEMF the offset is estimated. The control method is made robust at zero and low speed by changing the direct vector current component to a value different from zero. In order to verity the applicability of the method the controller has been implemented and tested on a 800 W motor.

Observer-Based Estimation of Stator-Winding Faults in Delta-Connected Induction Motors: A Linear Matrix Inequality Approach

This paper addresses the subject of interturn short circuit estimation in the stator of a delta-connected induction motor. In this paper, an adaptive observer scheme is proposed. The proposed observer is capable of simultaneously estimating the speed of the motor, the amount turns involved in the short circuit, and an expression of the current in the short circuit. Moreover, the states of the motor are estimated, meaning that the magnetizing currents are made available even though a fault has occurred in the motor. To be able to develop this observer, a model that is particularly suitable for the chosen observer design, is also derived. The efficiency of the proposed observer is demonstrated by tests performed on a test setup with a customized designed induction motor. With this motor it is possible to simulate interturn short-circuit faults.

Parameter estimation of inverter and motor model at standstill using measured currents only

Methods for the estimation of the parameters in the electrical equivalent diagram for an induction motor, based on especially designed experiments, are given. In all experiments, two of the three phases are given the same potential, i.e., no net torque is generated and the motor is at standstill. Input to the system is the reference values for the stator voltages given as duty cycles for the PWM power device. The system output is the measured stator currents. Three experiments are described giving respectively: (1) the stator resistance and inverter parameters; (2) the stator transient inductance; and (3) the referred rotor resistance and magnetizing inductance. The method developed in the two last experiments is independent of the inverter nonlinearity. New methods for system identification concerning saturation of the magnetic flux are given and a reference value for the flux level is derived. Experimental results are compared to factory measured values, and the difference may be explained by temperature variations and saturation effects.

Estimation of stator winding faults in induction motors using an adaptive observer scheme

This paper addresses the subject of inter-turn short circuit estimation in the stator of an induction motor. In the paper an adaptive observer scheme is proposed. The proposed observer is capable of simultaneously estimating the speed of the motor, the amount turns involved in the short circuit and an expression of the current in the short circuit. Moreover the states of the motor are estimated, meaning that the magnetizing currents are made available even though a fault has happened in the motor. To be able to develop this observer, a model particular suitable for the chosen observer design, is also derived. The efficiency of the proposed observer is demonstrated by tests performed on a test setup with a customized designed induction motor. With this motor it is possible to simulate inter-turn short circuit faults.

Thermal analysis of an HVAC system with TRV controlled hydronic radiator

A control oriented model for an HVAC system is derived in this paper. The HVAC system consists of a room and a hydronic radiator with a temperature regulating valve (TRV) which has a step motor to adjust the valve opening. The heating system and the room are simulated as a unit entity for thermal analysis and controller design. A discrete-element model with interconnected small scaled elements is proposed for the radiator. This models the radiator more precisely than that of a lumped model in terms of transfer delay and radiator gain. This precise modeling gives us an intuition into a regular unwanted phenomenon which occurs in low demand situations. When flow is very low in radiator and the supply water temperature and the pressure drop across the valve is constant, oscillations in room temperature frequently occur. The model derived in this paper demonstrates that the oscillations are in part due to the large gain of the radiator in low demand conditions compared to the high demand situations. The simulation model of radiator is optimized in terms of approximating the small signal gain of radiator in all operating points accurately. The controller designed for high demand weather conditions is applied to the opposite conditions to illustrate the oscillatory condition more apparently. Suggestions to alleviate this situation are proposed.