Spirometer system and method for determining lung functional residual capacity (FRC) with a non-occluding shutter

A flow tube apparatus provided for determining the lung Functional Residual Capacity (FRC), the apparatus comprising:

• a) a flow tube having a length defined between a distal end and a proximal end, having a substantially open lumen configured to allow air to flow from said proximal end to said distal end;
• said flow tube having a wall defined between an inner diameter and an outer diameter, wherein said inner diameter has at least one of the following profiles along the length of said open lumen:
• decreasing diameter, increasing diameter, hourglass profile, and wave like profile;
• b) a flow-meter positioned in a first recess disposed within said wall and a pressure sensor positioned in a second recess disposed within said wall;
• c) said flow tube configured to associate with a flow deflecting apparatus comprising:
• i) an axle disposed across the diameter of said lumen at a distance from said proximal end, said axle having a first end disposed within said flow tube wall and a second end extending through and transcending said flow tube wall, wherein said second end is adapted for associating with a deflector driver disposed externally to said flow tube;
• ii) wherein said deflector driver is adapted to drive said axle within said flow tube lumen in at least one direction;
• iii) said axle associated with a deflector leaf member provided for deflecting airflow within said flow tube characterized in that said leaf is configured not to occlude airflow through said flow-tube and therein allow flow through said tube so as to maintain normal breathing physiology along said flow-tube;
• and wherein said deflector leaf member may be controllably manipulated about said axle to assume at least two non-occluding positions within said flow tube, a first leaf position provided to maintain said flow-tube lumen substantially open and a second leaf position provided to deflect airflow through said flow tube;
• wherein said axle is adapted to allow both rotational and vertical movement of said leaf within said lumen.