Study objectives: To establish the value of electrical
impedance tomography (EIT) in assessing pulmonary edema in
noncardiogenic acute respiratory failure (ARF), as compared to the
thermal dye double indicator dilution technique (TDD).
Design: Prospective clinical study.
Setting: ICU of a general hospital.
Patients: Fourteen ARF patients.
Interventions: In order to use the TDD to determine the
amount of extravascular lung water (EVLW), a fiberoptic catheter was
placed in the femoral artery.
Measurements and main
results: Fourteen consecutive ARF patients receiving mechanical
ventilation were measured by EIT and TDD. EIT visualizes the impedance
changes caused by the ventilation in two-dimensional image planes. An
impedance ratio (IR) of the ventilation-induced impedance changes of a
posterior and an anterior part of the lungs was used to indicate the
amount of EVLW. For the 29 measurements in 14 patients, a significant
correlation between EIT and TDD (r = 0.85; p < 0.001) was found.
The EIT reproducibility was good. The diagnostic value of the
method was tested by receiver operator characteristic analysis, with 10
mL/kg of EVLW considered as the upper limit of normal. At a cutoff
level of the IR of 0.64, the IR had a sensitivity of 93%, a
specificity of 87%, and a positive predictive value of 87% for a
supranormal amount of EVLW. Follow-up measurements were
performed in 11 patients. A significant correlation was found between
the changes in EVLW measured with EIT and TDD (r = 0.85;
p < 0.005).
Conclusion: We conclude that EIT is a
noninvasive technique for reasonably estimating the amount of EVLW in