A simple method to estimate functional residual capacity in mechanically ventilated patients.
OBJECTIVE
The aim of the present study was to evaluate a simplified method for FRC measurement.


METHODS
Accuracy and precision of the method were assessed in a physical lung model; reproducibility was tested in 10 mechanically ventilated patients. In each patient FRC was measured at three PEEP levels.


METHODS
Post-operative intensive care unit in a university hospital.


RESULTS
Gas flow, CO2 concentration, and O2 concentration were measured during in- and expiration by pneumotachography, a mainstream capnometer and a sidestream O2-analyser. For FRC-measurement inspiratory O2 concentration was changed by 30%. FRC was determined as mean value of a N2 washout and N2 washin procedure. Evaluation of this method in a lung model shows a good correlation between FRC set in the lung model and FRC measured (FRC measured = 1.028*FRG model + 22.92 ml; r2 = 0.957; n = 30). The mean difference was 4.4% of FRC-reference (range -8.4% to +21.7%). Duplicate determinations in 10 mechanically ventilated patients differed by an average of -2.7% (range -30.1% to +27.3%).


CONCLUSIONS
Our results suggest that the proposed method can be used in daily clinical work.
Fretschner
R
R
Klinik für Anaesthesiologie und Transfusionsmedizin der Universität Tübingen.
Deusch
H
H
Weitnauer
A
A
Brunner
J X
JX
D000208:Acute Disease; D000328:Adult; D000368:Aged; D005652:Functional Residual Capacity; D006801:Humans; D007362:Intensive Care Units; D008722:Methods; D008875:Middle Aged; D008954:Models, Biological; D010100:Oxygen / Q000032:analysis; D011184:Postoperative Period; D015203:Reproducibility of Results; D012119:Respiration / Q000502:physiology*; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency / Q000628:therapy
D010100:Oxygen