title: Risk factors for aspiration.
abstract: BACKGROUND
  There are numerous risk factors for aspiration in tube-fed critically ill patients. However, there is confusion about the extent to which these factors actually contribute to aspiration. The purpose of this literature review was to summarize findings from selected research studies.
  
  
  METHODS
  A nonexhaustive literature search was conducted to identify risk factors for aspiration in tube-fed, critically ill patients. The most commonly cited factors were decreased level of consciousness, supine position, presence of a nasogastric tube, tracheal intubation and mechanical ventilation, bolus or intermittent feeding delivery methods, high-risk disease and injury conditions, and advanced age.
  
  
  RESULTS
  Many studies of aspiration risk factors have relatively small sample sizes and used equivocal definitions of aspiration. Although some addressed aspiration as an outcome, others considered gastroesophageal reflux or pneumonia as outcomes. Despite these variations, authors almost uniformly agree that a decreased level of consciousness and a sustained supine position are major risk factors for aspiration. There is less agreement regarding the effect of a nasogastric tube (or its size) on aspiration and on the effect of various formula delivery methods.
  
  
  CONCLUSIONS
  A decreased level of consciousness is a major risk factor for aspiration, as is a sustained supine position. Although some authors favor using small-bore feeding tubes to prevent aspiration, there seems to be insufficient data to warrant this action. Although strong data are lacking regarding feeding delivery methods, there are more data to support continuous feedings than bolus/intermittent feedings in high-risk patients.
authors.affiliation: School of Nursing, Saint Louis University, Missouri 63104-1099, USA. methenna@slu.edu
authors.forename: Norma A
authors.initials: NA
authors.lastname: Metheny
mesh_terms: D004750:Enteral Nutrition / Q000009:adverse effects*; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D011015:Pneumonia, Aspiration / Q000209:etiology*; D012307:Risk Factors