title: Mechanisms of gastroesophageal reflux in critically ill mechanically ventilated patients.
abstract: OBJECTIVE
  Gastroesophageal reflux is a major problem in mechanically ventilated patients and may lead to pulmonary aspiration and erosive esophagitis. Transient lower esophageal sphincter relaxations are the most common mechanism underlying reflux in nonventilated patients. The mechanisms that underlie reflux in critically ill ventilated patients have not been studied. The aim of this study was to determine the mechanisms underlying gastroesophageal reflux in mechanically ventilated patients in the intensive care unit.
  
  
  METHODS
  In 15 mechanically ventilated intensive care unit patients, esophageal motility, pH, and intraluminal impedance (11/15 patients) were recorded for 1 hour before and 5 hours during continuous nasogastric feeding.
  
  
  RESULTS
  Basal lower esophageal sphincter pressure was uniformly low (2.2 +/- 0.4 mmHg). The median (interquartile range) acid exposure (pH <4) was 39.4% (0%-100%) fasting and 32% (7.5%-94.2%) fed. Acid reflux occurred in 10 patients, but slow drifts in esophageal pH were also an important contributor to acid exposure. If esophageal pH decreased to pH <4, it tended to remain so for prolonged periods. A total of 46 acid reflux events were identified. Most (55%) occurred because of absent lower esophageal sphincter pressure alone; 45% occurred during straining or coughing.
  
  
  CONCLUSIONS
  Gastroesophageal reflux in mechanically ventilated patients is predominantly due to very low or absent lower esophageal sphincter pressure, often with a superimposed cough or strain. These data suggest that measures that increase basal LES pressure may be useful to prevent reflux in ventilated patients.
authors.affiliation: Department of Gastroenterology, Hepatology and General Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia.
authors.forename: Garry
authors.initials: G
authors.lastname: Nind
authors.forename: Wei-Hao
authors.initials: WH
authors.lastname: Chen
authors.forename: Richard
authors.initials: R
authors.lastname: Protheroe
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Iwakiri
authors.forename: Robert
authors.initials: R
authors.lastname: Fraser
authors.forename: Robert
authors.initials: R
authors.lastname: Young
authors.forename: Marianne
authors.initials: M
authors.lastname: Chapman
authors.forename: Nam
authors.initials: N
authors.lastname: Nguyen
authors.forename: Daniel
authors.initials: D
authors.lastname: Sifrim
authors.forename: Rachael
authors.initials: R
authors.lastname: Rigda
authors.forename: Richard H
authors.initials: RH
authors.lastname: Holloway
mesh_terms: D000328:Adult; D000368:Aged; D003371:Cough / Q000150:complications / Q000209:etiology; D016638:Critical Illness / Q000628:therapy*; D003679:Deglutition; D004943:Esophagogastric Junction / Q000503:physiopathology; D005260:Female; D005764:Gastroesophageal Reflux / Q000209:etiology* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000503:physiopathology; D011312:Pressure; D012121:Respiration, Artificial / Q000009:adverse effects*