Breathe easy: New research to improve inhaler effectiveness

Patients using dry powder inhalers to deliver medicine to their lungs need to breathe in at a “goldilocks” rate that is not too fast or too slow, and the drug particles need to be very fine – at around one micron – to be most effective, new research shows.

A dry powder inhaler (DPI) is a handheld device where you simply breathe in through the inhaler to deliver medicine directly to your lungs, unlike a ‘metred dose inhaler’ or ‘puffer’, which delivers aerosolised medicine from a pressurised canister.

“Inhalers were developed in the 1960’s to deliver medicine directly to the airways of people with lung diseases such as Asthma and COPD. They also hold potential to treat those with COVID-19,” said co-author Dr Suvash Saha from the University of Technology Sydney.

“However an inhaler that is not working efficiently can result in the drug being deposited mostly in the mouth and throat rather than in the deeper regions of the lungs, so the treatment is less effective,” he said.

Dr Saha, together with Dr Anurag Tiwari, Associate Professor Akshoy Ranjan Paul and Professor Anuj Jain from the Motilal Nehru National Institute of Technology Allahabad, India, used computation fluid dynamics to model how drugs are delivered to the human respiratory tract via a DPI device.

They examined three different drug particle sizes; 1, 5, and 10 microns, and three different inhalation rates; low, moderate and high, to determine how inhalers can be improved.

The study revealed that finer drug particles of around one micron are better able to travel further into the lungs than larger particle sizes.

They also found that the optimal inhalation rate that delivers the maximum amount of drug particles into the deeper airways of the lungs is one that is not too high or too low.

“At higher flow rates, more of the drug particles are deposited in the upper airways as they are more likely to impact with the walls of the airway,” said Dr Paul. 

“However, at lower flow rates there is not enough momentum to carry the drug particles to the deeper regions of the lungs,” he said.

This information will be important for designers of new dry powder inhalers, as well as for pharmacists wanting to improve drug formulations for delivery through these devices.

The findings have just been published in the paper ‘Computational Evaluation of Drug Delivery’ in the journal Physics of Fluids.

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