Researchers from the Harbin Institute of Technology in China created a model alveolar system for the field of biomicrofluidics that mimics the breathing activity of the human lung and permits observation of flow patterns within the alveoli. This device can be used to better understand how air and dust pass through the alveoli, making it useful in accurately diagnosing and treating respiratory conditions.

Heart Frontally
(Photo: No machine-readable author provided. Ekko assumed (based on copyright claims)/Wikimedia Commons)
Heart Frontally

What is Alveoli?

The main working parts of the human respiratory system are alveoli, which serve as small air sacs that exchange gases. According to Cancer.org, these are the sacs where blood and the lungs exchange oxygen and carbon dioxide when breathing in and out. Inhaled oxygen from the air travels to the body's tissues via the blood after passing through the alveoli. Blood carries carbon dioxide away from the body's tissues and through the alveoli to the lungs, where it is exhaled.

Model Alveolar Structure 

The researchers created a chip with tubes arranged to resemble the structure of a bronchial network bifurcation point. A flexible polymer shaped into tiny tubes resembling the alveolar structure makes up the chip's top layer. Since the lower layer is glass, the authors can see how fluid flows through the tubes.

The scientists created a system in which gas was compressed sinusoidal and pushed around the flexible tubes to simulate respiration. As a result, an inhaling and exhalation cycle is produced. 

The team added tiny red polystyrene spheres to the fluid running through tubes to observe flow patterns in the system. With the aid of these spheres, they could capture images of the fluid's motion as it was forced down the tubes by the artificial breathing system.

Flow Patterns on Alveoli Generation

The team discovered distinct flow patterns for several generations representing subsequent branches in the bronchial network. Alveoli begin to form in the human lung during generation 15 and continue to exist until generation 23. According to the study, the flow pattern changed between the 19th-20th and the 21st-22nd generations.

The 19th generation's alveolar flow is dominated by vortex flow, according to expert Yonggang Zhu. The 20th generation's alveolar flow patterns are compressed but similar to the 19th generation. The next generation had changed, according to the investigators.

The 21st-generation alveolar flow pattern combines radial and vortex flow. The radial flow region is substantially larger than the vortex region. Vortex flow vanishes when the flow reaches the 22nd generation, and all left is radial flow, according to Zhu.

The authors also discovered signs of disorderly behavior close to the vortex's center. They claimed that additional study is required to understand this completely, but they felt the current study serves as an excellent starting point for further research.

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Alveoli Model in Examining COPD and Emphysema

According to COPD News, patients with COPD experience impaired inflation and deflation of the alveoli, as well as irreversible damage to the air sac walls. As a result, the blood cannot get oxygen and cannot expel carbon dioxide as efficiently.

On the other hand, according to Mayo Clinic, emphysema damages the alveoli, which are the lungs' air sacs, to the point where they eventually rupture. This limits the amount of surface area accessible for gas exchange and instead creates one bigger air space rather than several smaller ones.

The model will enable researchers to examine how diseases like emphysema and COPD alter the flow patterns in the alveoli.

 

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