Performance testing system

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Overview
DDU testing for dry powder inhalers measures the dose emitted from the inhaler under controlled airflow conditions. Dry Powder Inhalers (DPIs) are passive, breath‑actuated devices that depend on the patient’s inspiratory effort rather than a propellant for aerosolisation and delivery. Device resistance, patient inspiratory effort and test flow rate are critical parameters that influence delivered dose for DPIs.

Key testing considerations
DPIs present varying internal flow resistances; some devices require higher inhalation effort than others. For reservoir‑type DPIs (multi‑dose devices with a reservoir), dose uniformity should be evaluated across the full contents of the inhaler to confirm consistency over product life. Test conditions should consider representative breathing profiles and appropriate mouthpiece interfaces.

Typical equipment and components used for DPI DDU testing

• Dose Uniformity Sampling Apparatus (DUSA) for DPIs — select DUSA type appropriate to inhaler geometry
• Mouthpiece adapters and mouthpiece adapter support fixtures
• Waste shot collectors (e.g. WSC2)
• Vacuum pump or high capacity pump (e.g. HCP7) to provide required suction where applicable
• Flow meters / flow rate sensors (e.g. Flow Rate Sensor FRS, DFM 2000)
• Critical flow controllers to measure/control pressure drop and flow conditions across the device (e.g. Critical Flow Controller TPK 200iX)
• Inhaler Testing Workstation (ITW) and ancillary stands/fixtures (e.g. DUSA Stand for DPIs)
• Environmental control accessories (temperature/humidity sensors, benchtop environmental chambers)

Related products and system elements commonly integrated into DPI DDU test systems

• Critical Flow Controller TPK 200iX
• High Capacity Pump HCP7
• Inhaler Testing Workstation (ITW)
• Dose Uniformity Sampling Apparatus (DUSA) for DPIs and DUSA Stand
• Flow Rate Sensor (FRS) and Flow Meter DFM 2000
• Waste Shot Collector WSC2
• Mouthpiece Adapter and Mouthpiece Adapter Support Accessory (fixtures for larger DPIs)
• Inhaler Support Accessory (fixture for multi‑dose disc‑shaped devices)

Automation and workflow
Automation options (for example DUSA Shaker™ DTS 100i and related automation for DDU testing) increase throughput, reduce handling variability and minimise manual errors during dose collection and drug recovery steps prior to assay. Automation also improves reproducibility when combined with standardised adapters and fixtures.

Applications
DDU testing of DPIs is used for product release, method development, generic development and bioequivalence studies, and for investigations into variability. For enhanced clinical relevance, some studies integrate realistic breathing profiles and throat or nasal models into DDU and APSD measurements.

Technical characteristics / specifications

• Device type: Dry Powder Inhalers (passive, breath‑actuated)
• Critical test parameters: inspiratory effort, device resistance, airtest flow rate, pressure drop across device
• Required sample collection: collection into DUSA tubes or collectors appropriate to inhaler type prior to assay
• Flow control: critical flow controller recommended to measure pressure drop and control flow (example: TPK 200iX)
• Pumps: high capacity or vacuum pumps used to provide repeatable suction for test conditioning (examples: HCP7)
• Data reproducibility: automation and standardised adapters/fixtures improve repeatability and reduce variability
• Environmental control: temperature and humidity sensors/chambers commonly used for controlled testing conditions