الفهرس 
Introduction
Energy requirementsOnly 14 pages are availabe for public view
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Abstract
Malnutrition can have deleterious effects on respiratory functions in general. In mechanically ventilated patients, this can manifest as impaired respiratory system immunity and difficult weaning from mechanical ventilation. Providing nutritional support is a corner stone in the care of mechanically ventilated patients regardless the cause of mechanical ventilation whether medical, surgical or traumatic.
Nutritional support can be achieved by providing properly calculated amounts of energy needs, macronutrients and micronutrients. Calculating energy needs in mechanically ventilated patients can be done by many methods, but best is through application of indirect calorimetry especially in the settings of difficult weaning where the need to avoid hypercaloric feeding is ultimate. Despite many controversies, the Harris-Benedict equation remains a simple and a relatively effective method for determining energy needs in absence of indirect calorimetry.
Nutritional assessment is an important component in any nutritional support program. It is employed to diagnose already existing malnutrition, to monitor the efficacy of nutritional support, and to detect possible complications. Nutritional assessment involves clinical history, physical examination, functional tests as well as laboratory investigations.
Providing nutritional support for mechanically ventilated patients through the enteral route whenever possible is currently preferred to the parenteral nutrition as it is more physiological and preserves gut mucosal integrity thus preventing bacterial translocation into the blood. Unless contraindicated enteral nutrition should be started within 48 hours after ICU admission.
Choice of access for enteral nutrition depends on many factors including anticipated duration of enteral nutritional support, state of gastrointestinal motility, risk of aspiration and available resources. Small intestinal feeding is preferred to gastric feeding in case of high risk for aspiration and intolerance to gastric feeding. When prolonged duration of enteral nutritional support is anticipated enterostomies are employed.
Choice of enteral feeding formula depends on gastrointestinal function, nutritional needs and associated medical conditions, but in general standard polymeric enteral formulas can be used in mechanically ventilated patients.
As any type of therapy, enteral nutritional support can have its margin of complications which precludes achieving goals of nutritional therapy. Diarrhea is the most commonly encountered complication of enteral feeding while delayed gastric emptying resulting in high gastric residuals is the most frequent cause for stopping enteral nutrition. Aspiration pneumonia is a serious complication of enteral nutrition but it can occur even in the absence of enteral feeding, many interventions can be employed to protect against aspiration pneumonia in mechanically ventilated patients but most important is backrest elevation. Application of a properly designed enteral nutrition protocol can help in minimizing complications and achieving desired goals.
Apart from using enteral formulas supplemented with ω-3 fatty acid in ARDS patients, the routine use of immune nutrients in mechanically ventilated patients may be unjustified and of questioned benefits.