LUNG DEPOSITION
FINE PARTICLE FRACTION
INTRODUCTION

For the treatment of asthma and COPD high drug concentrations at the site of disease are needed.1 One of the most important factors to determine lung deposition and therapeutic efficacy of inhalation therapy is the size of the inhaled particles containing the drugs.2 They differ in diameter from ≤1 µm up to 10 µm or even larger.

Optimal lung deposition is achieved when a high percentage of particles is between 1 and 5.8 µm in diameter.3 This is called the fine particle fraction of an aerosol (FPF). This FPF is influenced by the inhalation force of the patients in case of flow-dependent inhalers like dry powder inhalers (DPIs), whereas in flow-independent devices, like pressurized metered dose inhaler (pMDI) or soft mist inhaler (SMI), FPF is determined by device performance.4,5

HISTORIC FACT
The reduction of medicated liquid to fine droplets for inhalation was first applied with the invention and refinement of atomizers and nebulizers in the late 1800s. Nebulizers create aerosols with higher fractions of small droplets that are more likely to deposit in the lungs.8
PARTICLE SIZE AND LUNG DEPOSITION BY RESPIRATORY TRACT REGION
Particle Size
small
<1µm
medium
1 - 5.8 µm
large
>5.8 µm
Explanation of use
Inhalation simulator based on Demoly et al., 2014.5
This interactive simulator displays the effect of particle size on oropharyngeal deposition.
With the buttons, particle size can be varied in three steps: small (<1 µm), medium (1-5.8 µm), and large (>5.8 µm),
and the effect on particle deposition is shown.2,4,5
CONCLUSION

As demonstrated in the infographics, particle size strongly influences lung deposition.2 Drug particles of optimal size reach the alveolar region. Larger particles have a higher risk of impaction in the oropharyngeal region, and to some extent are deposited in the conducting airways. Particles that are too small, < 1 µm, have a greater chance than 40% to be exhaled.1,2,6

Even when FPF is optimal, lung deposition may not be efficient, because other device and patient factors also play a role.1,4,7 In the next scientific communication we will focus on spray-velocity and duration. Keep yourself posted!

Do you have questions about this Scientific Communication? Please do not hesitate to contact your local medical BI representative.