MRI Shows Lung Damage In Passive Smokers

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Main Category: Smoking / Quit Smoking
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Article Date: 27 Nov 2007 - 13:00 PDT

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A special type of MRI scan that uses colours to show damaged and undamaged areas of the lung has been used to show that non smokers suffer injury to their lungs from being exposed to second hand cigarette smoke for a long period of time.

These are the results of a study that was presented today, 27th November, to the annual meeting of the Radiological Society of North America (RSNA), in Chicago by lead researcher, Dr Chengbo Wang, a magnetic resonance physicist from the Department of Radiology at The Children's Hospital of Philadelphia in the US .

A colourful presentation of bright medical images showed the audience the extent of the damage deep in the lungs caused by inhaling second hand smoke. The damage is microscopic and not detectable with the usual medical imaging tools.

The researchers said this evidence should strengthen the case for authorities to tighten up regulations on second hand smoke.

Wang and colleagues used a special type of magnetic resonance imaging (MRI) to locate the tiny structural changes deep in the lungs. As Wang explained to the press:

"Almost one third of nonsmokers who had been exposed to secondhand cigarette smoke for a long time developed these structural changes."

Although the MRIs they looked at belonged to adults said Wang, the findings will also have implications for the 35 per cent of American children who breathe in smoke at home every day.

The researchers enrolled a total of 60 adults aged from 41 to 79, of which 45 had never smoked. The non smokers were grouped according to low and high exposure to second hand smoke. High exposure meant the participant had lived with a smoker for at least 10 years, often during childhood. The remaining 15 participants, all smokers, constituted a control group whose MRIs were used for comparison.

The participants inhaled a mixture of nitrogen and helium containing helium-3, an isotope obtained from polarising the gas to make it visible on the MRI scan. The MRI equipment used in this study measured diffusion, or the movement of individual atoms. In this case it measured the distance travelled by the isotope helium atoms in 1.5 seconds once inhaled into the lungs.

The helium atoms moved further in the non smokers who had been exposed to second hand smoke than in the lungs of normal subjects, suggesting the presence of holes and expansions in the alveoli. Alveoli are tiny breathing sacs in which inhaled oxygen passes into the bloodstream.

The results showed that nearly one third of the high exposure non smokers had structural changes in their lungs that were similar to those found in smokers.

"We interpreted those changes as early signs of lung damage, representing very mild forms of emphysema," said Wang.

Emphysema is a lung disease where the alveoli collapse making it very difficult to get enough oxygen into the bloodstream and to remove waste carbon dioxide from the bloodstream. It is commonly found in smokers and a major killer in the US, where nearly 14,000 people die from it every year.

The researchers also found a puzzling result among the remaining two thirds of the high exposure non smokers. Here they found diffusion distances shorter than those in the low exposure group. Perhaps the reason is this group was beginning to suffer a narrowing of the airways caused by the early stages of chronic bronchitis, another lung disease that is common among smokers.

Acknowledging the need for more studies to be done to replicate the findings and look more careful into the causes of the lung damage they observed, Wang said that:

"To our knowledge, this is the first imaging study to find lung damage in non smokers heavily exposed to secondhand smoke."

"We hope our work strengthens the efforts of legislators and policymakers to limit public exposure to secondhand smoke," added Wang.

Click here to learn more about emphysema (American Lung Association).

Written by: Catharine Paddock
Copyright: Medical News Today
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