Design and characteristics of a portable breath actuated, particle size selective medical aerosol inhaler

A new medical aerosol inhaler comprising a pressurized canister or metered dose inhaler (MDI), an aerosol holding chamber and a one-way valve system has been designed. Coordination of inhalation with actuation of the canister is no longer necessary as the valve ensures that aerosol is delivered only upon inspiration. The optimum chamber dimensions were found experimentally to be a cylinder approx. 11 cm in length by 3.5 cm diameter. It was deduced that the large particles from the MDI, which usually deposit in the upper airway during standard metered dose inhaler use, impacted in the holding chamber and the remainder evaporated to smaller size particles. These smaller particles (< 2.8 μ) remain suspended in the holding chamber, available for inhalation.