Approximately 40-50% of ICU patients are malnourished (1), which can be associated with the development of additional issues such as poor wound healing, increased risk of pressure ulcer development, weakened respiratory muscles, impaired immunity, organ dysfunction, and increased morbidity and mortality.
It is important to note that critical illness also significantly affects metabolism. Resting energy expenditure (REE), or the number of calories required by the body while at rest over a 24-hour period, generally increases in relation to burns, sepsis, trauma, and surgery. Registered dietitian nutritionists (RDNs) use predictive equations to assess the approximate REE of critically ill patients. A precise calculation of a patient's REE may help to prevent overfeeding or underfeeding of ICU patients, and potentially reduce the length-of-stay in the ICU as much as 2.9 days (2). Although that number of days does not sound very impressive it can add up to hundreds, of thousands - even millions - of dollars.
There are a great many equations which RDNs utilize for estimating REE in critically ill patients. Predictive equations are somewhat of a "one-size fits all" approach to patient care, and research studies have found these equations to be accurate about only 30% of the time (3). A more accurate approach to measuring REE is the metabolic cart, which uses indirect calorimetry to measure the oxygen consumption and carbon dioxide production of the patient. Every liter of oxygen consumed is equivalent to 5 calories (4).
In a perfect world, a metabolic cart study would be performed on every critically ill patient. However, there are several reasons why it is not always an option for estimating REE. The healthcare facility must first purchase a metabolic cart, which is costly. Larger hospitals are sometimes fortunate to have a budget which can support a costly purchase such as this, but unfortunately smaller hospitals do not always have this luxury. Specially trained staff is required for operation. which can be costly as well. Additionally, metabolic cart studies can be time consuming and may be difficult to achieve during daytime hours when staff is available. Finally, a steady state is required for the measurement to be valid, which can be difficult to accomplish with critically ill patients.
GE Healthcare has recently unveiled new ventilators for critical care which can improve the health of critically ill patients through a measured approach to nutrition - quite literally a measured approach to nutrition. The ventilator has the capability to use the respiratory gas module to calculate precise, real-time measurements of the critically ill patient's caloric requirements (3).
This new technology has the potential to guide RDNs in their quest to provide the best nutritional support possible for critically ill patients. Not to mention the potential to save millions of healthcare dollars.
1. Souba, W. Nutritional support. N Engl J Med 1997; 336: 41.
2. Neumayer LA, Smout RJ, Horn HG, Horn SD. Early and sufficient feeding reduces length of stay and charges in surgical patients. J Surg Res. 2001;95(1):73–77.
3. The Jewish Hospital Demonstrates Over 2-Day Reduction in ICU Length of Stay with GE Ventilation. July 2015.
4. Saenz AD. Metabolic Cart. Medscape. http://emedicine.medscape.com/article/2009552-overview. Published March 11, 2016. Accessed January 10, 2017.