A new apparatus for use in studies of the total and regional deposition of aerosol particles in the human respiratory tract during steady breathing

A new apparatus for use in combined studies of total and regional deposition has been constructed, which accurately samples the aerosol to be inhaled by means of a simple mechanical servomechanism and precision aerosol flow divider. Reversal of operation during expiration enables measurements to be taken during steady breathing. The sampling accuracy has been tested using a bag-in-a-box breathing simulator, which collects the “inhaled” aerosol for comparison with the predicted figure. The result of nine observations was a predicted figure of 100·02 ± 0·8% of the “inhaled” aerosol.

The exhaled aerosol particles are automatically separated for collection by means of two in-series valves controlled by a combination of volume limit switches and pressure changes near the mouth. Tidal volumes can, thus, be set to a predetermined value, enabling the subject to concentrate more effectively on the control of his respiratory flowrates and on minimizing his period of breath-holding.