Breathing patterns and ambient nanoparticle size affect interactions deep within the lungs

The human body takes in oxygen via the hundreds of millions of tiny air cavities called alveoli, whose fragile structures can be damaged by small particles. With widespread air pollution a constant global concern in public health, researchers are looking for ways to study this region of the respiratory system. Arefi et al. simulated the deposition of nanoparticles in lung-on-a-chip (LOAC) devices to better understand their impact on the tiny structures.

By varying particle size and taking specific types of breathing patterns into account, the authors were able to characterize the interplay and competing effects.

Specifically, they found activities that encourage breath-holding, like smoking and vaping, tend to increase nanoparticle deposition proportionally to the amount of time spent holding the breath. In the case of physical exercise, simulated by a higher breathing frequency, the faster and greater volumes of air flow also led to an uptick in particle deposition.

Particle size also plays a role, as it determines the type of motion the particle will undergo. In general, very fine (about 50 nanometers) and coarse (greater than 600 nanometers) particles are deposited the most. The deposition efficiency initially decreases with increasing particle size before reaching a minimum at about 200 nanometers, where gravitational effects begin to take over due to the greater mass.

“Some findings from this computer simulation may directly inform medical doctors’ decisions and recommendations,” said author Don Sin. He suggests individuals with pre-existing medical conditions consider restricting outdoor activities on days with heavy ambient air pollution.

Author James Feng said they hope these findings will improve future LOAC designs to accelerate the transition into clinical applications.

Source: “Simulation of nanoparticle transport and adsorption in a microfluidic lung-on-a-chip device,” by S. M. Amin Arefi, Cheng Wei Tony Yang, Don D. Sin, and James J. Feng, Biomicrofluidics (2020). The article can be accessed at https://doi.org/10.1063/5.0011353 .