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Current Affairs

Breathing rate and risk of coronavirus infection

Date: 16 January 2021 Tags: Miscellaneous

Issue

Researchers have found that a lower breathing frequency and holding one’s breath increases the risk of virus-laden droplets reaching the deep lung.

 

Background

Breathing slow can bring various health benefits but not as far as airborne transmission of disease is concerned. 

 

Details

  • Human bodies fight off much of the aerosols we inhale before they can deposit themselves in the inner lung, thanks to the complex geometry of the extrathoracic region and the lungs.

  • Part of the aerosols are flushed out in the form of mucus, while those that cross the nasal passage would still have to navigate the complex branching structure that define the lung.

  • The study looked at the dynamics of micrometre-sized droplets through such micro-channels, mimicking the lung environment. 

  • Transport of material or gases in the deep lung is purely diffusive. This diffusive nature ensures that gases are able to diffuse much faster than particles. This is part of the body’s own protection against aerosol particles reaching the blood.

  • Since different individuals are likely to have differing lung morphometry, their inherent protection is likely to be different.

  • This variability in aerosol uptake from individual to individual is a possible reason why some people are more susceptible to airborne diseases than others.

 

The findings

  • The experiments showed that low breathing frequency, the number of breaths per minute, increases the time the virus stays inside, and therefore increases the chances of deposition and consequently infection.

  • The research found a correlation between deposition and the aspect ratio of the capillaries, suggesting that droplets are likely to deposit in longer bronchioles.

  • Diffusion and impaction are two of the three mechanisms by which aerosols are deposited in various regions of the lung, the third being sedimentation.

  • Impaction happens when the droplets are moving so fast that they do not faithfully follow the air, and instead “impact” the walls of the bronchi.

  • Turbulence is the primary mode of deposition in the upper bronchi where the air velocity is high. But once the air reaches the deep lung, it is slowed down significantly, resulting in gas transport aided by diffusion.