When we inhale isolated coronavirus particles, more than 65% reach the deepest region of our lungs where cell damage can lead to low levels of oxygen in the blood, new research has found, and more of these aerosols reach the right lung than the left.
Lead author of the study, Dr Saidul Islam, Sydney University of Technology, said that while previous research has revealed how viral aerosols travel through the upper respiratory tract, including the nose , mouth and throat, this study was the first to examine how they circulate. the lower lungs.
“Our lungs look like tree branches that divide up to 23 times into smaller and smaller branches. Due to the complexity of this geometry, it is difficult to develop a computer simulation, but we were able to model it. happens in the first 17 generations, or branches, of the respiratory tract, ”said Dr. Islam.
“Depending on our breathing rate, between 32% and 35% of viral particles are deposited in these first 17 branches. This means that about 65% of viral particles escape to the deepest regions of our lungs, which includes the alveoli or air sacs. he said.
The alveolar system is essential for our ability to absorb oxygen, so significant amounts of virus in this area, along with the inflammation caused by our body’s immune response, can cause severe damage, reducing the amount of oxygen in the blood and increase the risk of death. .
The study also found that more viral particles are deposited in the right lung, especially the right upper lobe and right lower lobe, than in the left lung. This is due to the very asymmetric anatomical structure of the lungs and the way air circulates through the different lobes.
The research is supported by a recent study of chest CT scans of COVID-19 patients showing greater infection and disease in regions predicted by the model.
The researchers modeled three different flow rates: 7.5, 15 and 30 liters per minute. The model showed greater virus deposition at lower flow rates.
In addition to improving our understanding of coronavirus transmission, the findings have implications for the development of targeted drug delivery devices that can deliver drugs to areas of the respiratory system most affected by the virus.
“Normally, when we inhale drugs from a drug delivery device, most of it is deposited in the upper airways, and only a minimal amount of drugs can reach the targeted position of the lower airways. with diseases like COVID-19, we need to target the most affected areas, ”Dr Islam said.
“We are working to develop devices that can target specific regions, and we also hope to build age-specific and patient-specific whole lung models to better understand how SARS CoV-2 aerosols affect individual patients,” said the co-author and group leader of the Computer Simulations and Modeling Group at UTS, Dr Suvash Saha.
The World Health Organization recently updated its advice on the importance of aerosol transmission, warning that, as aerosols can remain airborne, overcrowded indoor environments and poorly ventilated areas present a risk. significant risk of transmission of Covid-19.
“When we use an aerosol deodorant, the smallest particles of this liquid fall on us under extreme pressure as a gas. Likewise, when an infected person speaks, sings, sneezes or coughs, the virus spreads throughout the body. ‘air and can infect those nearby,’ said Dr Saha.
The study has other applications, the researchers using portable devices to examine air quality – including the concentration of PM2.5 and PM10 and gases such as carbon dioxide, formaldehyde and carbon dioxide. sulfur – in spaces such as train cars. Researchers can then use this data to model the impact on our lungs.
The study, SARS CoV-2 aerosol: How far it can travel to the lower respiratory tract, was recently published in the journal Fluid physics.