Validation Data

Validation Data

Clement Clarke International have sought validation for the In-Check principle from the Aerosol Science Centre, AEA Technologies plc. This test house is an established centre for the calibration of cascade impactors, liquid impingers and other aerosol analysers, and is respected as a suitable third-party reference for Quality Assurance certification within the pharmaceutical industry.

AEA Technology website www.aeat.co.uk

Testing procedures report the flow/pressure profile for a number of sampled In-Check systems, against the actual inhaler devices flow/pressure readings. An example of one report is detailed below:-

EQUIPMENT Description>>>

The apparatus measures the air flow and pressure drop through a dry powder inhaler or an In-Check peak flow meter. The flow is measured by a fleisch tube connected to an electronic differential pressure sensor. The pressure is measured by an electronic pressure sensor connected to a T-piece placed between the fleisch tube and the test system. Both sensors are connected to an ADC board in a PC, recording data at 20Hz. The In-Check was connected to this system with a small section of rubber tubing. Particular care was taken to ensure an air tight seal.

Air was pulled through the system using a vacuum pump, with the airflow controlled by a needle valve.

CALIBRATION

The fleisch tube was calibrated by pulling air through several times using a 1.5 litre syringe. The pressure sensor was calibrated by pushing its sample tube into a measuring cylinder filled with water, and measuring the difference between the height of the water in the cylinder and the height of the water in the tube using the cylinder's graduated scale. The pressure sensor has been calibrated for linearity in a previous study.

MEASUREMENTS

For each inhaler/adapter measurements were taken for airflows of 0 l/min up to 80 l/min. Before each test, the inhaler was primed (where relevant), or the In-check system reset. The inhalers were always tested in their upright position, and the In-check tested in its horizontal position. The measurements were always started at 0 l/min, increasing to 80 l/min over about I minute. Data from the sensors was read directly into an excel spreadsheet, and averaged over 25 or 50 samples to improve readability of the graphs.

CALCULATIONS

Theory states that for a given resistance (k) the pressure drop will be proportional to the square of the airflow:

For each adapter setting of each In-check system the value of was calculated.

RESULTS

The results show that the In-Check systems matched the inhalers well, with good repeatability over the five systems checked.