Objective
Assessing limits of agreement with helium dilution and repeatability of a new system (lung funcution, LUFU) that measures
end-expiratory lung volume (EELV) in mechanically ventilated patients using the O2 washin (EELVWin) and washout (EELVWout) technique. LUFU consists of an Evita 4 ventilator, a side-stream oxygen analyzer, and a dedicated PC software.
Design and setting
Prospective human study in a general ICU of a University hospital.
Patients
Thirty-six mechanically ventilated patients.
Interventions
We obtained 36 couples of both EELVWin and EELVWout measurements in each patient (5 with healthy lungs, 9 with ALI, 22 with ARDS). Measurements were obtained with patients ventilated
either by assisted (ASB, 16 measurements) or controlled (CMV, 20 measurements) ventilation. In 19 of 20 cases in CMV, we obtained
helium dilution measurements (EELVHe).
Measurements and results
Bias for agreement with EELVHe was −16 ± 156 and 8 ± 161 ml, respectively, for EELVWin and EELVWout. Bias for agreement between EELVWin and EELVWout was 28 ± 78 and 23 ± 168 ml, respectively, for CMV and ASB. During CMV bias for repeatability were 8 ± 92 and 23 ± 165 ml,
respectively, for EELVWin and EELVWout. During ASB bias for repeatability were 32 ± 160 and −15 ± 147 ml, respectively, for EELVWin and EELVWout.
Conclusions
The LUFU method showed good agreement with helium, and good repeatability during partial and controlled mechanical ventilation.
The technique is simple and safe.
Keywords Oxygen washin–washout - Functional residual capacity - End-expiratory lung volume - Helium dilution - ARDS mechanical ventilation