Nutrition Monitoring and Feeding Optimization With the smART+ System

Mechanically ventilated patients are unable to take food orally and therefore are dependent on enteral nutrition for provision of both energy and protein requirements. The conditions of ICU patients dramatically change throughout their ICU stay; "diseases, like particularly sepsis, trauma and burns, cause clinically relevant increase in resting energy expenditure (REE) of between 40% - 80%," and most patients do not reach their required protein and caloric targets. The American association for Parenteral and Enteral Nutrition (ASPEN) recommends that for patients who are at high risk for malnutrition, efforts should be made to provide >80% of the estimated or calculated energy and protein goal within 48-72 hours, starting with half the patient's calorie goal with the rate slowly increasing over time, in order to achieve the clinical benefit of enteral nutrition over the first week of hospitalization. However, studies have shown that more than 74% of ICU patients failed to receive at least 80% of their prescribed nutrition.

Predictive equations (such as Harris-Benedict equation) or a simple weight-based formula (48.1% and 48.7% respectively) have therefore been the most practiced methods of determining energy needs; however, the literature clearly indicates that each equation has a large potential for error. This makes it difficult to accurately predict an individual patient's energy requirements during critical illness. In general, predictive equations estimate accurately only 50% of the time in ICU patients, leading to over or under evaluation of the nutritional needs and inducing over or underfeeding. Numerous meta-analyses have demonstrated the poor value of predictive equations variability that is increased because body weight remains a value difficult to accurately assess.

To overcome the inaccuracy in determining the patient's energy consumption and the accompanying problems, the European Society for Parenteral and Enteral Nutrition (ESPEN) guidelines recommend to determine patients' REE based on indirect calorimetry or VCO2-based equation (VCO2 x 8.19). Unfortunately, this is not performed continuously during the course of enteral feeding to assess the ever-changing nutritional needs of the patient. Estimations showed that only 2% of ICUs were regularly using REE / indirect calorimetry,11 and therefore they must resort to performing a one-time calculation of the patient's energy consumption to manually calculate the caloric intake, food type and feeding rate.

This study aims to assess the accuracy of the smART+ System's REE module, compared to (1) the FDA-cleared COSMED device, and (2) nutritional calculations conducted with predictive equations regularly used by the clinical staff at the site.