An Impactor is an instrument used to measure the size distribution of particles, particularly in pharmaceutical testing for inhalers and nebulizers. However, it’s important to understand that the Impactor does not simulate the lung—it’s primarily a tool to measure particle size distribution, not to replicate lung physiology.
Why?
- Impactors do not simulate how particles behave in the dynamic, moist, and moving environment of the lungs. The human lung involves mucus, cilia movement, moisture, air flow dynamics, and elasticity—none of which are present in an Impactor.
- In the lung, factors like airway humidity, branching airways, and lung tissue interactions significantly affect aerosol or powder deposition. These factors are not captured by the Impactor, which is essentially a static device.
- The Impactor operates under dry conditions, while the lungs have a moist surface that can change the behavior of particles through hygroscopic growth. They can increase in size due to moisture absorption, affecting where they deposit. Impactors cannot simulate these humid conditions or the interaction between particles and lung fluids.
- The Impactor assumes a constant and linear airflow, which does not mimic the complex and variable breathing patterns of a human.
- The purpose of the Impactor is to determine the in vitro aerodynamic particle size distribution of inhalable aerosols and powders. While this information helps predict whether particles are likely to reach the lungs, it doesn’t account for biological factors that influence actual deposition.
While Impactors do not simulate the complex environment of the lungs, they remain essential tools in Inhaler testing. They accurately measure the aerodynamic particle size distribution of aerosols/powders, which is crucial for predicting whether inhaled medications can reach the deeper parts of the respiratory tract. This information is vital for developing inhalers and nebulizers that deliver drugs effectively. Although they can’t replicate lung physiology, Impactors offer a standardized, controlled method for assessing particle size, ensuring consistency and reliability in testing before moving on to more complex, costly in vivo studies.
