1. Physical impairments that cause swallowing difficulties, dental disorders, dysphagia, stroke complication, or comatose states.
2. Upper GI problems such as esophageal fistula, partial obstructions in the esophagus or pylorus, and surgery or radiation therapy of upper GI tract, neck, or oropharynx.
3. Mental disturbances such as anorexia or depression.
4. Hyper metabolic states that produce increase nutritional needs such as burn, sepsis, multiple injuries, cancer, or hyperthyroidism.