title: Major influence of oxygen supply on 13CO2:12CO2 ratio measurement by nondispersive isotope-selective infrared spectroscopy.
abstract: BACKGROUND
  The nondispersive isotope-selective infrared spectroscopy (NDIRS) is a valid method for the measurement of the 13CO2:12CO2 ratio in breath samples. Methodical influences have to be considered to obtain valid results.
  
  
  OBJECTIVE
  To evaluate the effect of oxygen supply to patients on the measurement of 13C:12C ratio in breath samples by NDIRS.
  
  
  METHODS
  Breath samples of 26 healthy volunteers were taken before, immediately after, and 5 minutes after inhalation of 100% oxygen via a continuous positive air pressure (CPAP) mask. Analysis of breath samples was performed by NDIRS.
  
  
  RESULTS
  Delta per thousand before oxygen inhalation was -25.8 +/- 0.2. Immediately after 5 minutes of 100% oxygen inhalation, delta per thousand increased to -14.8 +/- 0.5 (delta over baseline [DOB] 11.0 +/- 0.4) and after additional 5 minutes of room air inhalation, delta per thousand normalized to -25.6 +/- 0.2 (DOB 0.2 +/- 0.1).
  
  
  CONCLUSIONS
  Oxygen supply to patients and, therefore, changes in gas composition in breath samples clearly influence 13CO2 measurement by NDIRS. This has to be taken into account in the clinical setting. Thus, oxygen supply during measurement of exhaled 13CO2 by NDIRS has to be avoided or maintained at a strictly constant level.
authors.affiliation: Department of General, Visceral and Transplantation Surgery, University Hospital Charité, Berlin, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Riecke
authors.forename: Peter
authors.initials: P
authors.lastname: Neuhaus
authors.forename: Martin
authors.initials: M
authors.lastname: Stockmann
mesh_terms: D000328:Adult; D001944:Breath Tests / Q000295:instrumentation / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis*; D002247:Carbon Isotopes / Q000032:analysis*; D002250:Carbon Radioisotopes / Q000032:analysis*; D005260:Female; D006801:Humans; D008297:Male; D010100:Oxygen / Q000008:administration & dosage / Q000494:pharmacology*; D013055:Spectrophotometry, Infrared / Q000295:instrumentation / Q000379:methods
chemical_list: D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D010100:Oxygen