ELFA 

           A new simple way to measure 

- FRC  (functional residual capacity) of the lung

   and

- CO  (cardiac output)  through lung perfusion

    The patented * measuring principle :

Allow rebreathing through a precisely known deadspace volume and measure the resulting rise in the end-expiratory carbon dioxide concentration.  From the shape of the increasing concentration, both FRC and CO can be deduced. See the schematic illustration below.