DDU of Dry Powder Inhalers (DPIs)

The basic requirements for DPI DDU testing are the same as for MDI testing, namely DUSA, mouthpiece adapter, vacuum pump and flow meter. However, a critical flow controller (e.g. Critical Flow Controller TPK 100i) to measure the pressure drop across the device and control the flow conditions during testing is also required. This is because most DPIs are passive breath-actuated devices which rely on the patient’s inspiration rather than a propellant for dose aerosolisation and delivery. The testing of DPIs is further complicated by the fact that different inhalers provide varying degrees of flow resistance, i.e. some require more effort to inhale through than others.