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


METHODS
Laboratory study and measurements in spontaneously breathing volunteers.


METHODS
Pulmonary function laboratory of a university hospital.


METHODS
20 healthy and 15 lung diseased volunteers.


METHODS
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 FiO(2) 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.


RESULTS
Repeatability of LUFU-FRC was estimated by comparing washin to washout and the different FiO(2)steps. 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).


CONCLUSIONS
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.
Maisch
Stefan
S
Department of Anaesthesiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany. smaisch@gmx.de.
Boehm
Stephan H
SH
Department of Anaesthesiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
Weismann
Dieter
D
Drägerwerk AG, Maislinger Allee 53-55, 23558, Lübeck, Germany.
Reissmann
Hajo
H
Department of Anaesthesiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
Beckmann
Marcus
M
Department of Anaesthesiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
Fuellekrug
Bernd
B
Department of Anaesthesiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
Meyer
Andreas
A
Department of Pneumology, Krankenhaus St. Kamillus, Kamillianerstr. 40-42, 41069, Mönchengladbach, Germany.
Schulte Am Esch
Jochen
J
Department of Anaesthesiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
D000328:Adult; D016001:Confidence Intervals; D004867:Equipment Design; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D008168:Lung / Q000502:physiology*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010993:Plethysmography, Whole Body / Q000379:methods*; D015203:Reproducibility of Results; D012122:Ventilators, Mechanical
D010100:Oxygen