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A shocking video shows the difference between healthy lungs and those of a smoker who got through one pack of cigarettes a day for 20 years.

Uploaded by North-Carolina based nurse Amanda Eller, the videos show the black, cancer-ridden lungs of a heavy smoker failing to properly inflate, the Daily Mail reports.

This is compared to the healthy, red-coloured lungs that are shown inflating and deflating as normal in the videos, which have been shared more than 5,000 times.

Around 15 percent of adults in the US and 17 percent in the UK smoke cigarettes.

Smoking raises a person's risk of developing lung cancer by approximately 23 times and is responsible for 87 percent of all related deaths.

Diseased lungs fail to fully inflate

While trying to inflate the blackened lungs, a woman, believed to be Ms Eller, said: "Because these lungs are COPD, cancerous lungs, the elastance is gone, so they will stretch out but then the recoil of them just snaps right back."

Elastance is the ability of lungs to rebound after being stretched during inhalation.

Reduced elastance suggests the lungs are stiff and have to work harder to bring in sufficient air, leaving individuals breathless.

When a PEP valve was fitted to the diseased lungs, their capacity to inflate slightly improved. A PEP valve helps to clear and open airways in cystic fibrosis patients.

The healthy, non-smoker's lungs filled to full capacity and then deflated slowly as normal. Photo / Facebook

These diseased lungs were then compared to healthy, red organs, which swelled to full capacity when filled with air.

Ms Eller added: "You can see [after] inhalation and [during] expiration [the lungs] totally deflate."

When a PEP valve was added to the healthy lungs, their rate of deflation slowed even more, which would allow people to absorb more oxygen.