title: 13CO2 breath tests, a tool to assess intestinal and liver function in the ICU?
abstract: OBJECTIVE
  CO2 breath tests, based on nondispersive infrared (NDIR) measurement technology, offer the chance for a noninvasive online quantitation of physiological processes. With recent extensions of the NDIR measurement technology breath tests could be used in an ICU setting without any restriction. Since online tools to assess feed intolerance with gastric emptying and to quantify gradual changes in liver function are still missing, this review explores the potential of breath tests to fill this gap.
  
  
  RESULTS
  Gastric emptying may be correctly quantified; however, the corresponding tests fail to capture aberrations in nutrient absorption, which appear to be linked to hyperglycemia and insulin resistance and may contribute to feed intolerance. The progression or ameloriation of liver injury could be assessed with breath tests, which cannot, however, distinguish between functional and macrocirculatory or microcirculatory disorders.
  
  
  CONCLUSIONS
  Breath tests for liver function and gastric emptying taken alone may fail in their ability to specifically quantify the clinical disorders. However, invasive test extensions could help to characterize their validity and thus to identify additional, noninvasive measurements to assure and expand this domain.
authors.affiliation: Klinik für Anästhesiologie, Universitätsklinikum, Ulm, Germany. josef.vogt@uni-ulm.de
authors.forename: Josef A
authors.initials: JA
authors.lastname: Vogt
authors.forename: Peter
authors.initials: P
authors.lastname: Radermacher
authors.forename: Michael
authors.initials: M
authors.lastname: Georgieff
mesh_terms: D001944:Breath Tests; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes; D005746:Gastric Emptying / Q000502:physiology*; D006801:Humans; D007362:Intensive Care Units; D007422:Intestines; D008833:Microcirculation; D008991:Monitoring, Physiologic
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide