1 Measurement of Functional Residual Capacity of the Lung by Nitrogen Washout/Wash-in in Mechanically Ventilated ICU Patients

Background: We evaluated the functionality, feasibility of use at the bedside and repeatability of subsequent Functional Residual Capacity (FRC) measurements in mechanically ventilated ICU patients using a new system. The newly developed system had previously been assessed for accuracy in spontaneously breathing human volunteers. Materials and Methods: We measured the FRC of the lungs of 20 mechanically ventilated ICU patients using the nitrogen washout/wash-in technique. Duplicate measures in each of the patients were analyzed for repeatability. Results: The squared correlation coefficient for the linear regression between repeated measurements was r2 = 0.92 (n = 39); y = 0.99