Intensive Care Medicine

, Volume 33, Issue 5, pp 912–916 | Cite as

Determination of functional residual capacity by oxygen washin-washout: a validation study

  • Stefan Maisch
  • Stephan H. Boehm
  • Dieter Weismann
  • Hajo Reissmann
  • Marcus Beckmann
  • Bernd Fuellekrug
  • Andreas Meyer
  • Jochen  Schulte am Esch
Technical Note



To validate a new system for functional residual capacity (FRC) measurements using oxygen washin/washout in spontaneously breathing humans. The system (LUFU, Drägerwerk AG, Lübeck, Germany) consists of an unmodified EVITA 4 ventilator, a side-stream paramagnetic oxygen sensor and a dedicated software.


Laboratory study and measurements in spontaneously breathing volunteers.


Pulmonary function laboratory of a university hospital.


20 healthy and 15 lung diseased volunteers.


FRC was measured by LUFU (LUFU-FRC) and by helium dilution (He-FRC); intra-thoracic gas volume (ITGV) was determined by body plethysmography. Each measurement cycle consisted of four independent LUFU-FRC determinations (step change of FiO2 from 0.21 to 0.5 and back and from 0.21 to 1.0 and back), two helium-dilution runs and two body box measurements. Repeatability and agreement between methods were determined by comparing different measurements of one technique and by comparing different techniques among each other.

Measurements and results

Repeatability of LUFU-FRC was estimated by comparing washin to washout and the different FiO2steps. The difference of the means was 3.7% at the most. Agreement between methods resulted in the following differences (mean ± standard deviation of differences) for healthy and lung-diseased volunteers, respectively: LUFU-FRC vs. He-FRC –0.40 ± 0.50 L (0.02 ± 0.95 L), LUFU-FRC vs. ITGV –0.43 ± 0.54 L (–0.18 ± 0.61 L) and He-FRC vs. ITGV –0.03 ± 0.43 L (–0.20 ± 0.98 L).


LUFU is a non-invasive method for the determination of FRC that requires only minor additional equipment and no modification to the ventilator. It can be used in difficult conditions such as breathing patterns with variations from breath to breath. The results of this study show that LUFU is sufficiently reliable and repeatable to warrant its clinical application.


Oxygen washin-washout Functional residual capacity Helium dilution method Body plethysmography 

Supplementary material

134_2007_578_MOESM1_ESM.pdf (874 kb)
Electronic Supplementary Material (PDF 890K)


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Stefan Maisch
    • 1
  • Stephan H. Boehm
    • 1
  • Dieter Weismann
    • 2
  • Hajo Reissmann
    • 1
  • Marcus Beckmann
    • 1
  • Bernd Fuellekrug
    • 1
  • Andreas Meyer
    • 3
  • Jochen  Schulte am Esch
    • 1
  1. 1.Department of AnaesthesiologyUniversity Medical Center Hamburg-EppendorfHamburgGermany
  2. 2.Drägerwerk AGLübeckGermany
  3. 3.Department of PneumologyKrankenhaus St. KamillusMönchengladbachGermany

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